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ARCHIMEDES, a Greek philosopher, studied about buoyancy. According to a legend, Archimedes was asked by king Hieron of Syracuse to determine whether his crown was made of pure gold or mixed with a less expensive metal. Thos was so big task for Archimedes that he was thinking of it all the time. He found the answer while he was taking a bath in the tub. Because of his great excitement, he ran in the streets shouting “EUREKA” , a great word meaning of “I found it”. He performed experiments and calculations and came up with what is now called “ARCHIMEDES PRINCIPLE” “The buoyant force of fluid on an object is equal to the weight of fluid the object is displaces”.
Archimedes’ principle applies to object that sink or float. An object sinks if its weight is greater than the buoyant force, however, it floats if its weight is less than buoyant force.
-(named after and denoted by the first letter in the Greek alphabet, α)
-it consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is produced in the process of alpha decay.
When an atom emits an alpha particle, the atom's mass number decreases by four due to the loss of the four nucleons in the alpha particle. The atomic number of the atom goes down by exactly two, as a result of the loss of two protons – the atom becomes a new element.
Examples: when uranium becomes thorium, or radium becomes radon gas due to alpha decay.
Alpha particles are commonly emitted by all of the larger radioactive nuclei such as uranium, thorium, actinium, and radium, as well as the transuranic elements. Unlike other types of decay, alpha decay as a process must have a minimum-size atomic nucleus which can support it. The smallest nuclei which have to date been found to be capable of alpha emission are the lightest nuclides of tellurium (element 52), with mass numbers between 106 and 110. The process of emitting an alpha sometimes leaves the nucleus in an excited state, with the emission of a gamma ray removing the excess energy. Energetic helium nuclei may be produced by cyclotrons, synchrotrons, and other particle accelerators, but they are not normally referred to as alpha particles. As noted, helium nuclei may participate in nuclear reactions in stars, and occasionally and historically these have been referred to, as alpha reactons (see triple alpha process.)
Because of the short range of absorption, alphas are not generally dangerous to life unless the source is ingested or inhaled, in which case, they become extremely dangerous. Because of this high mass and strong absorption, if alpha emitting radionuclides do enter the body (if the radioactive material has been inhaled or ingested), alpha radiation is the most destructive form of ionizing radiation. It is the most strongly ionizing, and with large enough doses can cause any or all of the symptoms of radiation poisoning. It is estimated that chromosome damage from alpha particles is about 100 times greater than that caused by an equivalent amount of other radiation. The powerful alpha emitter polonium-210 (a milligram of 210Po emits as many alpha particles per second as 4.215 grams of 226Ra) is suspected of playing a role in lung cancer and bladder cancer related to tobacco smoking.[4] 210Po was used to kill Russian dissident and ex-FSB officer Alexander V. Litvinenko in 2006.[5] Not only do alphas themselves cause damage, but approximately equal ionization is caused by the recoiling nucleus after alpha emission, and this energy may in turn be especially damaging to genetic material, since the positive cations of many soluble transuranic elements which emit alphas, are chemically attracted to the net negative charge of DNA, causing the recoiling atomic nucleus to be in close proximation to the DNA.
Protons Electrons and Neutrons What are protons, neutrons and electrons?
Everything around us- air, water, sand, stone, wood, plants, animals, humans- scientists call them all matter.
When we analyze the structure of matter, we see that all matter is made essentially of about a hundred pure substances called elements in different combinations. Some elements do not combine with others and stay in pure form. But in most cases, two or more elements combine to form different substances. These combined substances are called compounds.
For example, the water we drink is a compound of two elements- hydrogen and oxygen. Our common table salt is nothing but a compound of the elements sodium and chlorine. But beware, sugar is a little more complicated - it has carbon in addition to hydrogen and oxygen! Many substances around us, especially the things that make up plant and animal matter, are far more complicated.
But the fact remains- complicated or simple, all matter is made up of elements. Each element is unique- it has its own special qualities. When you break up these elements into smaller and smaller pieces, you will finally get a tiny speck called an atom. Atom is the limit- you cannot break up the atom of an element and expect to see that element’s special qualities continued.
For a long time scientists believed that it is not possible to break up an atom. However some great scientists like J.J. Thomson, Goldstein and Chadwick later discovered that atoms are made up of three particles called Protons, Neutrons and Electrons. These particles are today called sub-atomic particles.
Protons, neutrons and electrons are very tiny particles. They are many times smaller than the smallest speck we can see with our naked eyes. The weight of a proton is somewhat close to the weight of a hydrogen atom, which is the smallest of all atoms. The weight of a neutron is almost the same as a proton. If you divide the weight of a hydrogen atom by 1837, you will get the weight of an electron. Thus electron is the lightest of the subatomic particles.
Of these three particles, protons and electrons have electrical charge on them. Each proton has one unit positive charge on it. Each electron holds one unit of negative charge. Neutrons are not charged particles. The number of protons and electrons in an atom is equal, so they cancel out each other and thus the atom does not have electrical charge on it.
When we speak of things like weight in our everyday life, we use units like grams and kilograms to measure them. We talk of electricity in terms of amperes and watts. However the world of protons, neutrons and electrons is so small we cannot use these units to show their weight or electric charge. Scientists use special units to talk about them.
Protons and neutrons always stay together at the centre of an atom. This part is called the nucleus. The electrons go on circling around the nucleus at very high speeds through special tracks called orbits. This might remind you of our solar system where the planets go on orbiting the sun. Well, the picture is pretty similar except that one is very huge and the other is very tiny.
We found that each atom is made of protons, electrons and neutrons. The atoms of each element have a different number of protons and electrons. No two different elements can have the same number of protons and electrons in their atoms. Hydrogen has one proton and electron in its atom and helium has two protons and electrons in its atom. Oxygen has eight protons and electrons in its atom. Thus it is the number of protons and electrons in the atom that makes each element unique. Scientists explain each element’s behavior using the number of protons, electrons and neutrons it has.
We found earlier that all matter is made up of atoms. Now that we know of protons, neutrons and electrons, we can modify our statement. All matter, everything we see around us, is made up of protons, neutrons and electrons!
Potential energy is energy that is stored within a system. It exists when there is a force that tends to pull an object back towards some lower energy position. This force is often called a restoring force. For example, when a spring is stretched to the left, it exerts a force to the right so as to return to its original, unstretched position. Similarly, when a mass is lifted up, the force of gravity will act so as to bring it back down. The initial action of stretching the spring or lifting the mass both require energy to perform. The energy that went into lifting up the mass is stored in its position in the gravitational field, while similarly, the energy it took to stretch the spring is stored in the metal. According to the principle of conservation of energy, energy cannot be created or destroyed; hence this energy cannot disappear. Instead, it is stored as potential energy. If the spring is released or the mass is dropped, this stored energy will be converted into kinetic energy by the restoring force, which is elasticity in the case of the spring, and gravity in the case of the mass. Think of a roller coaster. When the coaster climbs a hill it has potential energy. At the very top of the hill is its maximum potential energy. When the car speeds down the hill potential energy turns into kinetic. Kinetic energy is greatest at the bottom.
The more formal definition is that potential energy is the energy difference between the energy of object in a given position and its energy at a reference position.
There are various types of potential energy, each associated with a particular type of force. More specifically, every conservative force gives rise to potential energy. For example, the work of an elastic force is called elastic potential energy; work of the gravitational force is called gravitational potential energy; work of the Coulomb force is called electric potential energy; work of the strong nuclear force or weak nuclear force acting on the baryon charge is called nuclear potential energy; work of intermolecular forces is called intermolecular potential energy. Chemical potential energy, such as the energy stored in fossil fuels, is the work of the Coulomb force during rearrangement of mutual positions of electrons and nuclei in atoms and molecules. Thermal energy usually has two components: the kinetic energy of random motions of particles and the potential energy of their mutual positions.
DENSITY is a physical property of matter, as each element and compound has a unique density associated with it. Density defined in a qualitative manner as the measure of the relative "heaviness" of objects with a constant volume.
For example: A rock is obviously more dense than a crumpled piece of paper of the same size. A styrofoam cup is less dense than a ceramic cup.
Density may also refer to how closely "packed" or "crowded" the material appears to be - again refer to the styrofoam vs. ceramic cup.
Density Comparison to Water: In chemistry, the density of many substances is compared to the density of water. Does an object float on water or sink in the water? If an object such as a piece of wood floats on water it is less dense than water vs. if a rock sinks, it is more dense than water.
Density examples:
Oil and vinegar salad dressing: The oil floats on the vinegar water mixture, while the solids sink to the bottom. Oil spills: What happens when an oil tanker leaks on the ocean? The oil floats on the water since it is less dense, and this provides some opportunity to clean up the oil spills by skimming the oil from the surface of the water.
Ice: Everyone knows that ice floats on water, but did you know that this is an abnormal physical property of solid/liquid state of water? The more normal physical property is for the solid of a compound to sink in its own liquid.
Demonstrations with Density
Mysterious Ice Layers of Liquids Egg Densities - sugar water/oil Smart Eggs - salt water and acid Floating Eggs - sugar and water Floating Spheres Lava Lamp Underwater Smoke Stack Floating objects in water
Mathematical Definition of Density
The formal definition of density is mass per unit volume. Usually the density is expressed in grams per mL or cc. Mathematically a "per" statement is translated as a division. cc is a cubic centimeter and is equal to a mL Therefore,
Density = mass/volume = g/mL
In order to determine the density of an object, it is necessary to know: the mass, the volume of the substance, and the definition of density.
Density = mass (g) volume (mL)
Mass vs. Weight: Although the terms mass and weight are used almost interchangeably, there is a difference between them. Mass is a measure of the quantity of matter, which is constant all over the universe. Weight is proportional to mass but depends on location in the universe. Weight is the force exerted on a body by gravitational attraction (usually by the earth).
Example: The mass of a man is constant. However the man may weigh: 150 lbs on earth, 25 lbs on the moon (because the force of gravity on the moon is 1/6 that of the earth), and be "weightless" in space.
A magnetic monopole is a hypothetical physics particle with only one magnetic pole.
Normally, magnets have two "charges" - a north pole and a south pole - which mean that, overall, the magnetic charge of the magnet cancels out.
Magnetic monopoles, on the other hand, behave more like electrical charge, which have a net positive or negative charge.
Magnetic monopoles were originally proposed by Pierre Curie. Paul Dirac developed a quantum physical theory of monopoles in 1931. Since electrical charges are quantized, Dirac was able to show that the existence of magnetic monopoles is consistent with existing laws of physics.
Many current theories (such as string theory) in physics predict that in the high energy state of the early universe, shortly after the big bang, magnetic monopoles would have existed in nature. If these theories are correct, it would take more powerful particle accelerators to generate the magnetic monopoles.
In addition, it is possible to create effective magnetic monopoles within certain types of materials, so that the north and south poles move freely within the material, instead of in coupled pairs.
YOUNG'S EXPERIMENT Young's experiment) demonstrates the inseparability of the wave and particle natures of light and other quantum particles. A coherent light source illuminates a thin plate with two parallel slits cut in it, and the light passing through the slits strikes a screen behind them. The wave nature of light causes the light waves passing through both slits to interfere, creating an interference pattern of bright and dark bands on the screen. However, at the screen, the light is always found to be absorbed as though it were made of discrete particles, called photons.
If the light travels from the source to the screen as particles, then on the basis of a classical reasoning the number that strike any particular point on the screen is expected to be equal to the sum of those that go through the left slit and those that go through the right slit. In other words, according to classical particle physics the brightness at any point should be the sum of the brightness when the right slit is blocked and the brightness when the left slit is blocked. However, it is found that unblocking both slits makes some points on the screen brighter, and other points darker. This can only be explained by the alternately additive and subtractive interference of waves, not the exclusively additive nature of particles, so we know that light must have some particle-wave duality.
Any modification of the apparatus that can determine which slit a photon passes through destroys the interference pattern, illustrating the complementarity principle; that the light can demonstrate both particle and wave characteristics, but not both at the same time. However, an experiment performed in 1987 produced results that demonstrated that which-path information could be obtained without destroying the possibility of interference. This showed the effect of measurements that disturbed the particles in transit to a lesser degree and thereby influenced the interference pattern only to a comparable extent.
The double slit experiment can also be performed (using different apparatus) with particles of matter such as electrons with the same results, demonstrating that they also show particle-wave duality.
A Carbon footprint is the amount of greenhouse gas emissions caused by an indidual, organization, or event, an individual, nation or organization carbon.
This carbon footprint came from the humans activities on there environment and in terms of greenhouse gases produced, measured in units of carbon dioxide.'' if you will calculate the measure of carbon footprint i think this is just the right time, hoping its not too late, to take a clear and determined look just responsible to keep this planet liveable for the generation to come? and also can measured the particular climate changed the carbon footprint can be relates to the amount of greenhouse gases that produced in our day to day lives though its burning fossil fuel for elecricity heating and transportation.
The carbon footprint is a measurement of all greenhouse gases we individually produce and has unit of tonnes ( or kg) of carbon dioxide equivalent.
Evidence of global warming cause of greenhouse effect and carbon footprint by measuring it.
global warming is the same given by scientist for the gradual increase in temperature of the earth's surface that has worsened since the industrial revolution.
as the years goes by the measured and amount of pullution getting bigger and larger. the evidence considerable exists the most of this warming that caused by human activities the effects of the enlargement of the pollution.
this are the altrede chemical composition from the atmosphere. the pollution give by car's even the perfume, alcohol, pestiside, methane and nitrous oxide etc. this are the only example of air pollution. that calculate by carboon footprint
many questions has there no answer's? many people are still hoping for a better lifestyle? what if we do nothing?
what if we do nothing?????? people always saying..
if we could do nothing to the global warming it will rise temperature that will cause sea level and local climate conditions . if this will be happened the forests, crop yeilds, water supplies and also affects human helath, animals, and many types in ecosystem.
The total amount of greenhouse gases produced to directly and indirectly support human activities, usually expressed in equivalent tons of carbon dioxide (CO2).
In other words When you drive a car, the engine burns fuel which creates a certain amount of CO2, depending on its fuel consumption and the driving distance. (CO2 is the chemical symbol for carbon dioxide). When you heat your house with oil, gas or coal, then you also generate CO2. Even if you heat your house with electricity, the generation of the electrical power may also have emitted a certain amount of CO2. When you buy food and goods, the production of the food and goods also emitted some quantities of CO2.
The attached Excel sheet can be used to calculate both CO2 emissions as well as primary energy requirements for the following activities:
*Heating with oil, *coal, *wood, *solar energy or heat pumps *Electricity consumption.
The actual mix of power generation (coal, oil, natural gas, wood, nuclear energy, hydro energy, solar energy, wind, geothermal or waste) is taken into consideration. Travelling by car for diesel and petrol fuelled cars. Either by actual fuel consumption or by distance and average fuel consumption. *Travelling by bus (kilometres or miles) *Travelling by train (kilometres or miles)
..... we need to save the world..... ..... for the safetiness of all....
The term magnetism is used to describe how materials respond on the microscopic level to an applied magnetic field; to categorize the magnetic phase of a material. For example, the most well known form of magnetism is ferromagnetism such that some ferromagnetic materials produce their own persistent magnetic field. However, all materials are influenced to greater or lesser degree by the presence of a magnetic field. Some are attracted to a magnetic field (paramagnetism); others are repulsed by a magnetic field (diamagnetism); others have a much more complex relationship with an applied magnetic field. Substances that are negligibly affected by magnetic fields are known as non-magnetic substances. They include copper, aluminium, water, and gases.
The magnetic state (or phase) of a material depends on temperature (and other variables such as pressure and applied magnetic field) so that a material may exhibit more than one form of magnetism depending on its temperature, etc.
SOURCES OF MAGNETISM...
There exists a close connection between angular momentum and magnetism, expressed on a macroscopic scale in the Einstein-de Haas effect "rotation by magnetization" and its inverse, the Barnett effect or "magnetization by rotation".
At the atomic and sub-atomic scales, this connection is expressed by the ratio of magnetic moment to angular momentum, the gyromagnetic ratio.
Magnetism, at its root, arises from two sources:
* Electric currents or more generally, moving electric charges create magnetic fields (see Maxwell's Equations). * Many particles have nonzero "intrinsic" (or "spin") magnetic moments. (Just as each particle, by its nature, has a certain mass and charge, each has a certain magnetic moment, possibly zero.)
In magnetic materials, sources of magnetization are the electrons' orbital angular motion around the nucleus, and the electrons' intrinsic magnetic moment (see Electron magnetic dipole moment). The other potential sources of magnetism are the nuclear magnetic moments of the nuclei in the material which are typically thousands of times smaller than the electrons' magnetic moments, so they are negligible in the context of the magnetization of materials. (Nuclear magnetic moments are important in other contexts, particularly in Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI).)
Ordinarily, the countless electrons in a material are arranged such that their magnetic moments (both orbital and intrinsic) cancel out. This is due, to some extent, to electrons combining into pairs with opposite intrinsic magnetic moments (as a result of the Pauli exclusion principle; see Electron configuration), or combining into "filled subshells" with zero net orbital motion; in both cases, the electron arrangement is so as to exactly cancel the magnetic moments from each electron. Moreover, even when the electron configuration is such that there are unpaired electrons and/or non-filled subshells, it is often the case that the various electrons in the solid will contribute magnetic moments that point in different, random directions, so that the material will not be magnetic.
However, sometimes (either spontaneously, or owing to an applied external magnetic field) each of the electron magnetic moments will be, on average, lined up. Then the material can produce a net total magnetic field, which can potentially be quite strong.
The magnetic behavior of a material depends on its structure (particularly its electron configuration, for the reasons mentioned above), and also on the temperature (at high temperatures, random thermal motion makes it more difficult for the electrons to maintain alignment).
Diamagnetism appears in all materials, and is the tendency of a material to oppose an applied magnetic field, and therefore, to be repelled by a magnetic field. However, in a material with paramagnetic properties (that is, with a tendency to enhance an external magnetic field), the paramagnetic behavior dominates.[9] Thus, despite its universal occurrence, diamagnetic behavior is observed only in a purely diamagnetic material. In a diamagnetic material, there are no unpaired electrons, so the intrinsic electron magnetic moments cannot produce any bulk effect. In these cases, the magnetization arises from the electrons' orbital motions, which can be understood classically as follows:
When a material is put in a magnetic field, the electrons circling the nucleus will experience, in addition to their Coulomb attraction to the nucleus, a Lorentz force from the magnetic field. Depending on which direction the electron is orbiting, this force may increase the centripetal force on the electrons, pulling them in towards the nucleus, or it may decrease the force, pulling them away from the nucleus. This effect systematically increases the orbital magnetic moments that were aligned opposite the field, and decreases the ones aligned parallel to the field (in accordance with Lenz's law). This results in a small bulk magnetic moment, with an opposite direction to the applied field.
Note that this description is meant only as an heuristic; a proper understanding requires a quantum-mechanical description.
Note that all materials undergo this orbital response. However, in paramagnetic and ferromagnetic substances, the diamagnetic effect is overwhelmed by the much stronger effects caused by the unpaired electrons.
PARAMAGNETISM...
In a paramagnetic material there are unpaired electrons, i.e. atomic or molecular orbitals with exactly one electron in them. While paired electrons are required by the Pauli exclusion principle to have their intrinsic ('spin') magnetic moments pointing in opposite directions, causing their magnetic fields to cancel out, an unpaired electron is free to align its magnetic moment in any direction. When an external magnetic field is applied, these magnetic moments will tend to align themselves in the same direction as the applied field, thus reinforcing it.
FERROMAGNETISM...
A ferromagnet, like a paramagnetic substance, has unpaired electrons. However, in addition to the electrons' intrinsic magnetic moments tendency to be parallel to an applied field, there is also in these materials a tendency for these magnetic moments to orient parallel to each other to maintain a lowered energy state. Thus, even when the applied field is removed, the electrons in the material maintain a parallel orientation.
Every ferromagnetic substance has its own individual temperature, called the Curie temperature, or Curie point, above which it loses its ferromagnetic properties. This is because the thermal tendency to disorder overwhelms the energy-lowering due to ferromagnetic order.
Some well-known ferromagnetic materials that exhibit easily detectable magnetic properties (to form magnets) are nickel, iron, cobalt, gadolinium and their alloys.
The magnetic moment of atoms in a ferromagnetic material cause them to behave something like tiny permanent magnets. They stick together and align themselves into small regions of more or less uniform alignment called magnetic domains or Weiss domains. Magnetic domains can be observed with a magnetic force microscope to reveal magnetic domain boundaries that resemble white lines in the sketch.There are many scientific experiments that can physically show magnetic fields. Effect of a magnet on the domains.
When a domain contains too many molecules, it becomes unstable and divides into two domains aligned in opposite directions so that they stick together more stably as shown at the right.
When exposed to a magnetic field, the domain boundaries move so that the domains aligned with the magnetic field grow and dominate the structure as shown at the left. When the magnetizing field is removed, the domains may not return to an unmagnetized state. This results in the ferromagnetic material's being magnetized, forming a permanent magnet.
When magnetized strongly enough that the prevailing domain overruns all others to result in only one single domain, the material is magnetically saturated. When a magnetized ferromagnetic material is heated to the Curie point temperature, the molecules are agitated to the point that the magnetic domains lose the organization and the magnetic properties they cause cease. When the material is cooled, this domain alignment structure spontaneously returns, in a manner roughly analogous to how a liquid can freeze into a crystalline solid.
ANTIFERROMAGNETISM...
In an antiferromagnet, unlike a ferromagnet, there is a tendency for the intrinsic magnetic moments of neighboring valence electrons to point in opposite directions. When all atoms are arranged in a substance so that each neighbor is 'anti-aligned', the substance is antiferromagnetic. Antiferromagnets have a zero net magnetic moment, meaning no field is produced by them. Antiferromagnets are less common compared to the other types of behaviors, and are mostly observed at low temperatures. In varying temperatures, antiferromagnets can be seen to exhibit diamagnetic and ferrimagnetic properties.
In some materials, neighboring electrons want to point in opposite directions, but there is no geometrical arrangement in which each pair of neighbors is anti-aligned. This is called a spin glass, and is an example of geometrical frustration.
FERRIMAGNETISM...
Like ferromagnetism, ferrimagnets retain their magnetization in the absence of a field. However, like antiferromagnets, neighboring pairs of electron spins like to point in opposite directions. These two properties are not contradictory, because in the optimal geometrical arrangement, there is more magnetic moment from the sublattice of electrons that point in one direction, than from the sublattice that points in the opposite direction.
The first discovered magnetic substance, magnetite, was originally believed to be a ferromagnet; Louis Néel disproved this, however, with the discovery of ferrimagnetism.
-->is the physics of electromagnetic field,a field that exerts a force on charged particles and is reciprocally affected by the presence and motion of such particles..
...a changing magnetic field produces an electric field(this is the phenomenon of electromagnetic induction the basis of operation for electrical generators,induction motors and transformers)Similarly a changing electric field generates a magnetic field.
...The magnetic field is produce by the motion of electrical charges.Thee magnetic field causes the magnetic force associated with magnets.
...The theoritical implication of electromagnetism led to the development of special relativity by Albert Einstein in 1905 and from this is was shown the magnetic fields and electric fields are convertible with relative motion as a four vector
...For humans, population density is the number of people per unit of area usually per square kilometer or mile (which may include or exclude cultivated or potentially productive area). ... Commonly this may be calculated for a county, city, country, another territory, or the entire world.
...The world population is 6.8 billion [1], and Earth's area is 510 million square kilometers (197 million square miles) [2] . Therefore the worldwide human population density is 6.8 billion ÷ 510 million = 13.1 per km² (34.0 per sq. mile), or 44.7 per km² (115.5 per sq. miles) if only the Earth's land area of 150 million km² (58 million sq. miles) is taken into account. This density rises when the population grows. It also includes all continental and island land area, including Antarctica. ...Considering that over half of the Earth's land mass consists of areas inhospitable to human inhabitation, such as deserts and high mountains, and that population tends to cluster around seaports and fresh water sources, this number by itself does not give any meaningful measurement of human population density.
...Several of the most densely-populated territories in the world are city-states, microstates, micronations, or dependencies. These territories share a relatively small area and a high urbanization level, with an economically specialized city population drawing also on rural resources outside the area, illustrating the difference between high population density and overpopulation.
...Cities with high population densities are, by some, considered to be overpopulated, though the extent to which this is the case depends on factors like quality of housing and infrastructure or access to resources. Most of the most densely-populated cities are in southern and eastern Asia, though Cairo and Lagos in Africa also fall into this category.
..City population is, however, heavily dependent on the definition of "urban area" used: densities are often higher for the central municipality itself, than when more recently-developed and administratively unincorporated suburban communities are included, as in the concepts of agglomeration or metropolitan area, the latter including sometimes neighboring cities. For instance, Milwaukee has a greater population density when just the inner city is measured, and not the surrounding suburbs as well.
this is the formula!!!!!^_^v
Mathematically:
\rho = \frac{m}{V} \,
where:
ρ (rho) is the density, m is the mass, V is the volume.
...Different materials usually have different densities, so density is an important concept regarding buoyancy, metal purity and packaging.
...In some cases density is expressed as the dimensionless quantities specific gravity (SG) or relative density (RD), in which case it is expressed in multiples of the density of some other standard material, usually water or air/gas.
In electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. The term usually refers to a semiconductor diode, the most common type today, which is a crystal of semiconductor connected to two electrical terminals, a P-N junction. A vacuum tube diode, now little used, is a vacuum tube with two electrodes; a plate and a cathode.
The most common function of a diode is to allow an electric current in one direction (called the diode's forward direction) while blocking current in the opposite direction (the reverse direction). Thus, the diode can be thought of as an electronic version of a check valve. This unidirectional behavior is called rectification, and is used to convert alternating current to direct current, and remove modulation from radio signals in radio receivers.
However, diodes can have more complicated behavior than this simple on-off action, due to their complex non-linear electrical characteristics, which can be tailored by varying the construction of their P-N junction. These are exploited in special purpose diodes that perform many different functions. Diodes are used to regulate voltage (Zener diodes), electronically tune radio and TV receivers (varactor diodes), generate radio frequency oscillations (tunnel diodes), and produce light (light emitting diodes).
Zone melting or zone refining or floating zone process) is a group of similar methods of purifying crystals, in which a narrow region of a crystal is molten, and this molten zone is moved along the crystal (in practice, the crystal is pulled through the heater). The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot. The impurities concentrate in the melt, and are moved to one end of the ingot. Zone refining was developed by William Gardner Pfann in Bell Labs as a method to prepare high purity materials for manufacturing transistors. Its early use was on germanium for this purpose, but it can be extended to virtually any solute-solvent system having an appreciable concentration difference between solid and liquid phases at equilibrium [1]. This process is also known as the float zone process, particularly in semiconductor materials processing.
Another related process is zone remelting, in which two solutes are distributed through a pure metal. This is important in the manufacture of semiconductors, where two solutes of opposite conductivity type are used. For example, in germanium, pentavalent elements of group V such as antimony and arsenic produce negative (n-type) conduction and the trivalent elements of group III such as aluminum and boron produce positive (p-type) conduction. By melting a portion of such an ingot and slowly refreezing it, solutes in the molten region become distributed to form the desired n-p and p-n junctions.
Aberrations are departures of the performance of an optical system from the predictions of paraxial optics.[1] Aberration leads to blurring of the image produced by an image-forming optical system. It occurs when light from one point of an object after transmission through the system does not converge into (or does not diverge from) a single point. Instrument-makers need to correct optical systems to compensate for aberration. The articles on reflection, refraction and caustics discuss the general features of reflected and refracted rays.
Aberration is something that deviates from the normal way but has several specifically defined meanings:
* Optical aberration, an imperfection in image formation by an optical system * Spherical aberration, which occurs when light rays strike a lens or mirror near its edge * Chromatic aberration, caused by differences in refractive index for different wavelengths of light * Defocus aberration, which occurs when a system is out of focus
The aberration of light (also referred to as astronomical aberration or stellar aberration) is an astronomical phenomenon which produces an apparent motion of celestial objects about their real locations. It was discovered and later explained by the third Astronomer Royal, James Bradley, in 1725, who attributed it to the finite speed of light and the motion of Earth in its orbit around the Sun.
At the instant of any observation of an object, the apparent position of the object is displaced from its true position by an amount which depends solely upon the transverse component of the velocity of the observer, with respect to the vector of the incoming beam of light (i.e., the line actually taken by the light on its path to the observer). The result is a tilting of the direction of the incoming light which is independent of the distance between object and observer.
In the case of an observer on Earth, the direction of a star's velocity varies during the year as Earth revolves around the Sun (or strictly speaking, the barycenter of the solar system), and this in turn causes the apparent position of the star to vary. This particular effect is known as annual aberration or stellar aberration, because it causes the apparent position of a star to vary periodically over the course of a year. The maximum amount of the aberrational displacement of a star is approximately 20 arcseconds in right ascension or declination. Although this is a relatively small value, it was well within the observational capability of the instruments available in the early eighteenth century.
Aberration should not be confused with stellar parallax, although it was an initially fruitless search for parallax that first led to its discovery. Parallax is caused by a change in the position of the observer looking at a relatively nearby object, as measured against more distant objects, and is therefore dependent upon the distance between the observer and the object.
In contrast, stellar aberration is independent of the distance of a celestial object from the observer, and depends only on the observer's instantaneous transverse velocity with respect to the incoming light beam, at the moment of observation. The light beam from a distant object cannot itself have any transverse velocity component, or it could not (by definition) be seen by the observer, since it would miss the observer. Thus, any transverse velocity of the emitting source plays no part in aberration. Another way to state this is that the emitting object may have a transverse velocity with respect to the observer, but any light beam emitted from it which reaches the observer, cannot, for it must have been previously emitted in such a direction that its transverse component has been "corrected" for. Such a beam must come "straight" to the observer along a line which connects the observer with the position of the object when it emitted the light.
Aberration should also be distinguished from light-time correction, which is due to the motion of the observed object, like a planet, through space during the time taken by its light to reach an observer on Earth. Light-time correction depends upon the velocity and distance of the emitting object during the time it takes for its light to travel to Earth. Light-time correction does not depend on the motion of the Earth—it only depends on Earth's position at the instant when the light is observed. Aberration is usually larger than a planet's light-time correction except when the planet is near quadrature (90° from the Sun), where aberration drops to zero because then the Earth is directly approaching or receding from the planet. At opposition to or conjunction with the Sun, aberration is 20.5" while light-time correction varies from 4" for Mercury to 0.37" for Neptune (the Sun's light-time correction is less than 0.03").
refers to various phenomena which occur when a wave encounters an obstacle.
It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Similar effects are observed when light waves travel through a medium with a varying refractive index or a sound wave through one with varying acoustic impedance. Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, x-rays and radio waves. As physical objects have wave-like properties (at the atomic level), diffraction also occurs with matter and can be studied according to the principles of quantum mechanics.
While diffraction occurs whenever propagating waves encounter such changes, its effects are generally most pronounced for waves where the wavelength is on the order of the size of the diffracting objects. If the obstructing object provides multiple, closely-spaced openings, a complex pattern of varying intensity can result. This is due to the superposition, or interference, of different parts of a wave that traveled to the observer by different paths (see diffraction grating).
The formalism of diffraction can also describe the way in which waves of finite extent propagate in free space. For example, the expanding profile of a laser beam, the beam shape of a radar antenna and the field of view of an ultrasonic transducer are all explained by diffraction theory.
..The proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom, along with neutrons, but is also stable by itself and has a second identity as the hydrogen ion, H+. It is composed of three fundamental particles: two up quarks and one down quark.[3] Contents [hide]
* 1 Description * 2 Stability * 3 Quarks and the mass of the proton * 4 The proton in chemistry o 4.1 Atomic number o 4.2 Hydrogen as proton * 5 History * 6 Exposure * 7 Antiproton * 8 See also * 9 References * 10 External links
[edit] Description
Protons are spin-½ fermions and are composed of three quarks,[4] making them baryons. The two up quarks and one down quark of the proton are held together by the strong force, mediated by gluons.[3] The proton has an approximately exponentially decaying positive charge distribution with a mean square radius of about 0.8 fm.[5]
Protons and neutrons are both nucleons, which may be bound by the nuclear force into atomic nuclei. The nucleus of the most common isotope of the hydrogen atom is a single proton (it contains no neutrons). The nuclei of heavy hydrogen (deuterium and tritium) contain neutrons. All other types of atoms are composed of two or more protons and various numbers of neutrons. The number of protons in the nucleus determines the chemical properties of the atom and thus which chemical element is represented; it is the number of both neutrons and protons in a nuclide which determine the particular isotope of an element. [edit] Stability Main article: Proton decay
Protons are observed to be stable and their empirically observed half-life is at least 6.6×1035 years.[6] Grand unified theories generally predict that proton decay should take place, although experiments so far have only resulted in a lower limit of 1035 years for the proton's lifetime. In other words, proton decay has never been witnessed and the experimental lower bound on the mean proton lifetime (2.1×1029 years) is given by the Sudbury Neutrino Observatory.[7]
The volume of any solid, liquid, gas, plasma, or vacuum is how much three-dimensional space it occupies, often quantified numerically. One-dimensional figures (such as lines) and two-dimensional shapes (such as squares) are assigned zero volume in the three-dimensional space. Volume is commonly presented in units such as cubic meters, cubic centimeters, liters, or milliliters.
Volumes of some simple shapes, such as regular, straight-edged, and circular shapes can be easily calculated using arithmetic formulas. More complicated shapes can be calculated by integral calculus if a formula exists for its boundary. The volume of any shape can be determined by displacement.
In differential geometry, volume is expressed by means of the volume form, and is an important global Riemannian invariant.
Volume is a fundamental parameter in thermodynamics and it is conjugate to pressure.
Magnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field.
For the physics of magnetic materials, see magnetism and magnet, more specifically ferromagnetism, paramagnetism, and diamagnetism. For constant magnetic fields, such as are generated by magnetic materials and steady currents, see magnetostatics. A changing magnetic field generates an electric field and a changing electric field results in a magnetic field. (See electromagnetism.)
In view of special relativity, the electric and magnetic fields are two interrelated aspects of a single object, called the electromagnetic field. A pure electric field in one reference frame is observed as a combination of both an electric field and a magnetic field in a moving reference frame.
In modern physics, the magnetic (and electric) fields are understood to be due to a photon field; in the language of the Standard Model the electromagnetic force is mediated by photons. Most often this microscopic description is not needed because the simpler classical theory covered in this article is sufficient; the difference is negligible under most circumstances.
(often abbreviated E-M radiation or EMR) is a phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It consists of electric and magnetic field components which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. Electromagnetic radiation is classified into several types according to the frequency of its wave; these types include (in order of increasing frequency and decreasing wavelength): radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. A small and somewhat variable window of frequencies is sensed by the eyes of various organisms; this is what is called the visible spectrum, or light. EM radiation carries energy and momentum that may be imparted to matter with which it interacts.
theory:
Electromagnetic waves were first postulated by James Clerk Maxwell and subsequently confirmed by Heinrich Hertz. Maxwell derived a wave form of the electric and magnetic equations, revealing the wave-like nature of electric and magnetic fields, and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave. According to Maxwell's equations, a spatially-varying electric field generates a time-varying magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form an electromagnetic wave. A quantum theory of the interaction between electromagnetic radiation and matter such as electrons is described by the theory of quantum electrodynamics.
Energy is the vital force powering business, manufacturing, and the transportation of goods and services to serve the American and world economies. Energy supply and demand plays an increasingly vital role in our national security and the economic output of our nation. It is not surprising that the United States spends over 500 billion dollars annually on energy.
purple electricity emanating from a center ball
Increasing energy supplies. As America's need for energy grows, the Department of Energy is meeting the challenge by establishing clean fuel initiatives to make the most of traditional fossil fuels while investing in cutting edge research to develop sustainable sources such as fusion and to employ hydrogen (an energy carrier like electricity) which can be produced from diverse, domestic sources and greatly reduce our dependence on imported oil. part of industrial building
Modernizing our energy infrastructure. By developing the infrastructure to support these fuels, DOE is striving every day to protect our nation's energy needs and our planet's environment. ripples in a pool of water
Ensuring the productive and optimal use of energy resources, while limiting environmental impact. In addition, the Department of Energy is harnessing the power of the earth itself to meet our energy needs. Advances in wind, hydro and geothermal energy allow us to take advantage of clean, abundant energy. honeycomb against a black background
Cooperating on international energy issues. The Department’s activities are instrumental in establishing the safety, reliability, and efficiency of energy supplies in a global marketplace.
A completely submerged body displaces a volume of liquid equal to itsown volume. Experience also tell us that when an object is submerged, itappear lighter in weight; the water buoys it up, pushed upward, partiallysupporting it somehow. Archimedes' Buoyancy Principle asserts that
an object immersed in a liquid will be lighter by an amountequal to the weight of the fluid it displaces.
The upward force exerted by the fluid is known as buoyant force.
Buoyant force is caused by gravity acting on the fluid. It has its originin the pressure difference occurring between the top and bottom of theimmersed object, a difference that always exists when pressure varies withdepth. Imaging without the object, the same immersed space will be occupiedby the same volume of fluid. The weight of those fluid is supported by other parts of the fluid.So the buoyant force is the weight of the displaced fluid. I hope thisjava applet will help you learn more about buoyancy.
said... force... In physics, the concept of force is used to describe an influence which causes a free massive body to undergo an acceleration. Forces which do not act uniformly on all parts of a body will also cause mechanical stresses.[1]
Force can also be described by intuitive concepts such as a push or pull that can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate, or which can cause a flexible object to deform. Related concepts to accelerating forces include thrust - any force which increases the velocity of the object, drag - any force which decreases the velocity of any object, and torque - the tendency of a force to cause changes in rotational speed about an axis. Alternatively, mechanical stress is a technical term for the efforts which cause deformation of matter, be it solid, liquid, or gaseous. While mechanical stress can remain embedded in a solid object, gradually deforming it, mechanical stress in a fluid determines changes in its pressure and volume.[2][3]
An applied force has both magnitude and direction, making it a vector quantity. Newton's second law states that an object with a constant mass will accelerate in proportion to the net force acting upon and in inverse proportion to its mass. Equivalently, the net force, on an object equals the rate at which its momentum changes.[4]
Philosophers in antiquity have used the concept of force in the study of stationary and moving objects. Aristotle attempted to define this concept in detail but incorporated fundamental misunderstandings that lasted many centuries. Archimedes developed a better understanding of force by observing simple machines, but many in his time still believed Aristotle's concept of force.[5] When the Age of Enlightenment began, Sir Isaac Newton corrected these misunderstandings with mathematical insight that remained unchanged for nearly three hundred years.[3] By the early 20th century, Einstein developed the theory of Special Relativity to correctly predict how forces increase exponentially for particles approaching the speed of light.
With modern insights into quantum mechanics and technology that can accelerate particles close to the speed of light, particle physics has devised a Standard Model to describe forces between particles smaller than atoms. The Standard Model predicts that exchange particles called gauge bosons are the fundamental means by which forces are emitted and absorbed. Only four main interactions are known: in order of decreasing strength, they are: strong, electromagnetic, weak, and gravitational.[2] High-energy particle physics observations made during the 1970s and 1980s confirmed that the weak and electromagnetic forces are expressions of a more fundamental electroweak interaction.[6]
Conservation of energy The law of conservation of energy is an empirical law of physics. It states that the total amount of energy in an isolated system remains constant over time (is said to be conserved over time). A consequence of this law is that energy can neither be created nor destroyed, it can only be transformed from one state to another. The only thing that can happen to energy in a closed system is that it can change form, for instance chemical energy can become kinetic energy.
Albert Einstein's theory of relativity shows that energy and mass are the same thing, and that neither one appears without the other. Thus in closed systems, both mass and energy are conserved separately, just as was understood in pre-relativistic physics. The new feature of relativistic physics is that "matter" particles (such as those constituting atoms) could be converted to non-matter forms of energy, such as light; or kinetic and potential energy (example: heat). However, this conversion does not affect the total mass of systems, since the latter forms of non-matter energy still retain their mass through any such conversion.
Today, conservation of “energy” refers to the conservation of the total system energy over time. This energy includes the energy associated with the rest mass of particles and all other forms of energy in the system. In addition the invariant mass of systems of particles (the mass of the system as seen in its center of mass inertial frame, such as the frame in which it would need to be weighed), is also conserved over time for any single observer, and (unlike the total energy) is the same value for all observers. Therefore, in an isolated system, although matter (particles with rest mass) and "pure energy" (heat and light) can be converted to one another, both the total amount of energy and the total amount of mass of such systems remain constant over time, as seen by any single observer. If energy in any form is allowed to escape such systems (see binding energy) the mass of the system will decrease in correspondence with the loss. Principle of physics according to which the energy of interacting bodies or particles in a closed system remains constant, though it may take different forms (e.g., kinetic energy, potential energy, thermal energy, energy in an electric current, or energy stored in an electric field, in a magnetic field, or in chemical bonds [see bonding]). With the advent of relativity physics in 1905, mass was recognized as equivalent to energy. When accounting for a system of high-speed particles whose mass increases as a consequence of their speed, the laws of conservation of energy and conservation of mass become one conservation law. The principle of conservation of energy states that energy cannot be created or destroyed, although it can be changed from one form to another. Thus in any isolated or closed system, the sum of all forms of energy remains constant. The energy of the system may be interconverted among many different forms—mechanical, electrical, magnetic, thermal, chemical, nuclear, and so on—and as time progresses, it tends to become less and less available; but within the limits of small experimental uncertainty, no change in total amount of energy has been observed in any situation in which it has been possible to ensure that energy has not entered or left the system in the form of work or heat. For a system that is both gaining and losing energy in the form of work and heat, as is true of any machine in operation, the energy principle asserts that the net gain of energy is equal to the total change of the system's internal energy.
Voltage is electric potential energy per unit charge, measured in joules per coulomb ( = volts). It is often referred to as "electric potential", which then must be distinguished from electric potential energy by noting that the "potential" is a "per-unit-charge" quantity. Like mechanical potential energy, the zero of potential can be chosen at any point, so the difference in voltage is the quantity which is physically meaningful. The difference in voltage measured when moving from point A to point B is equal to the work which would have to be done, per unit charge, against the electric field to move the charge from A to B.
The voltage between two (electron) positions "A" and "B", inside a solid electrical conductor (or inside two electrically-connected, solid electrical conductors), is denoted by (VA − VB). This voltage is the electrical driving force that drives a conventional electric current in the direction A to B. Voltage can be directly measured by a voltmeter. Well-constructed, correctly used, real voltmeters approximate very well to ideal voltmeters. An analogy involving the flow of water is sometimes helpful in understanding the concept of voltage.
Voltage, also called electromotive force, is a quantitative expression of the potential difference in charge between two points in an electrical field. The greater the voltage, the greater the flow of electrical current (that is, the quantity of charge carriers that pass a fixed point per unit of time) through a conducting or semiconducting medium for a given resistance to the flow. Voltage is symbolized by an uppercase italic letter V or E. The standard unit is the volt, symbolized by a non-italic uppercase letter V. One volt will drive one coulomb (6.24 x 1018) charge carriers, such as electrons, through a resistance of one ohm in one second.
Voltage can be direct or alternating. A direct voltage maintains the same polarity at all times. In an alternating voltage, the polarity reverses direction periodically. The number of complete cycles per second is the frequency, which is measured in hertz (one cycle per second), kilohertz, megahertz, gigahertz, or terahertz. An example of direct voltage is the potential difference between the terminals of an electrochemical cell. Alternating voltage exists between the terminals of a common utility outlet.
A voltage produces an electrostatic field, even if no charge carriers move (that is, no current flows). As the voltage increases between two points separated by a specific distance, the electrostatic field becomes more intense. As the separation increases between two points having a given voltage with respect to each other, the electrostatic flux density diminishes in the region between them.
Just before the First World War, two German scientists, James Franck and Gustav Hertz, carried out experiments where they bombarded mercury atoms with electrons and traced the energy changes that resulted from the collisions. Their experiments helped to substantiate they theory put forward by Nils Bohr that an atom can absorb internal energy only in precise and definite amounts.
In 1921 two Otto Hahn and Lise Meitner, discovered nuclear isomers. Over the next few years they devoted their time to researching the application of radioactive methods to chemical problems. In the 1930s they became interested in the research being carried out by Enrico Fermi and Emilio Segre at the University of Rome. This included experiments where elements such as uranium were bombarded with neutrons. By 1935 the two men had discovered slow neutrons, which have properties important to the operation of nuclear reactors.
Otto Hahn and Lise Meitner were now joined by Fritz Strassmann and discovered that uranium nuclei split when bombarded with neutrons. In 1938 Meitner, like other Jews in Nazi Germany, was dismissed from her university post. She moved to Sweden and later that year she wrote a paper on nuclear fission with her nephew, Otto Frisch, where they argued that by splitting the atom it was possible to use a few pounds of uranium to create the explosive and destructive power of many thousands of pounds of dynamite.
In January, 1939 a Physics Conference took place in Washington in the United States. A great deal of discussion concerned the possibility of producing an atomic bomb. Some scientists argued that the technical problems involved in producing such a bomb were too difficult to overcome, but the one thing they were agreed upon was that if such a weapon was developed, it would give the country that possessed it the power to blackmail the rest of the world. Several scientists at the conference took the view that it was vitally important that all information on atomic power should be readily available to all nations to stop this happening.
On 2nd August, 1939, three Jewish scientists who had fled to the United States from Europe, Albert Einstein, Leo Szilard and Eugene Wigner, wrote a joint letter to President Franklin D. Roosevelt, about the developments that had been taking place in nuclear physics. They warned Roosevelt that scientists in Nazi Germany were working on the possibility of using uranium to produce nuclear weapons. Roosevelt responded by setting up a scientific advisory committee to investigate the matter. He also had talks with the British government about ways of sabotaging the German efforts to produce nuclear weapons.
In May, 1940, the German Army invaded Denmark, the home of Niels Bohr, the world's leading expert on atomic research. It was feared that he would be forced to work for Nazi Germany. With the help of the British Secret Service he escaped to Sweden before being moving to the United States.
In 1942 the Manhattan Engineer Project was set up in the United States under the command of Brigadier General Leslie Groves. Scientists recruited to produce an atom bomb included Robert Oppenheimer (USA), David Bohm (USA), Leo Szilard (Hungary), Eugene Wigner (Hungary), Rudolf Peierls (Germany), Otto Frisch (Germany), Niels Bohr (Denmark), Felix Bloch (Switzerland), James Franck (Germany), James Chadwick (Britain), Emilio Segre (Italy), Enrico Fermi (Italy), Klaus Fuchs (Germany) and Edward Teller (Hungary).
Winston Churchill and Franklin D. Roosevelt were deeply concerned about the possibility that Germany would produce the atom bomb before the allies. At a conference held in Quebec in August, 1943, it was decided to try and disrupt the German nuclear programme.
In February 1943, SOE saboteurs successfully planted a bomb in the Rjukan nitrates factory in Norway. As soon as it was rebuilt it was destroyed by 150 US bombers in November, 1943. Two months later the Norwegian resistance managed to sink a German boat carrying vital supplies for its nuclear programme.
Lenz's Law >A law of electromagnetism which states that,whenever there is an induced electromotive force(emf)in a conductor,it is alaways in such a direction that the current it would produce would oppose the change which causes the induced emf.If the change is the motion of a conductor through a magnetic field, the induced current must be in such a direction as to produce aforce opposing the motion .If the change causing the emf is a change of flux threading a coil, the induced current must produce a flux in such a direction as to oppose the change.Lenz's law is a form of the law of conversation of energy ,since it states that a change cannot propagate itself.
Distance and displacement are different quantities, but they are related. If you take the first example of the walk around the desk, it should be apparent that sometimes the distance is the same as the magnitude of the displacement. This is the case for any of the one meter segments but is not always the case for groups of segments. As I trace my steps completely around the desk the distance and displacement of my journey soon begin to diverge. The distance traveled increases uniformly, but the displacement fluctuates a bit and then returns to zero.
Distance is a scalar measure of the interval between two locations measured along the actual path connecting them. Displacement is a vector measure of the interval between two locations measured along the shortest path connecting them.
In the case of one and the same uniform motion, the distance traversed during a longer interval of time is greater than the distance traversed during a shorter interval of time.
Formula: D= (S)(T), Distance =Speed x Time
example:
Mr. Smiths bike travels at an average of 8km/hr. If he rides to Coach Anderson's house 24 km away, how long does it take to get there? T=D/S 24 km/8kmhr=
The density of a material is defined as its mass per unit volume. The symbol of density is ρ (the Greek letter rho).
Formula
Mathematically:
\rho = \frac{m}{V} \,
where:
ρ (rho) is the density, m is the mass, V is the volume.
Different materials usually have different densities, so density is an important concept regarding buoyancy, metal purity and packaging.
In some cases density is expressed as the dimensionless quantities specific gravity (SG) or relative density (RD), in which case it is expressed in multiples of the density of some other standard material, usually water or air/gas.
History
In a well-known tale, Archimedes was given the task of determining whether King Hiero's goldsmith was embezzling gold during the manufacture of a wreath dedicated to the gods and replacing it with another, cheaper alloy.[1]
Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass; but the king did not approve of this.
Baffled, Archimedes took a relaxing immersion bath and observed from the rise of the warm water upon entering that he could calculate the volume of the gold crown through the displacement of the water. Allegedly, upon this discovery, he went running naked through the streets shouting, "Eureka! Eureka!" (Εύρηκα! Greek "I found it"). As a result, the term "eureka" entered common parlance and is used today to indicate a moment of enlightenment.
The story first appeared in written form in Vitruvius' books of architecture, two centuries after it supposedly took place.[2] Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time.
Measurement of density
For a homogeneous object, the mass divided by the volume gives the density. The mass is normally measured with an appropriate scale or balance; the volume may be measured directly (from the geometry of the object) or by the displacement of a fluid. Hydrostatic weighing is a method that combines these two.
If the body is not homogeneous, then the density is a function of the position: \rho(\vec{r})=dm/dv, where dv is an elementary volume at position \vec{r}. The mass of the body then can be expressed as
m = \int_V \rho(\vec{r}) dV
The density of a solid material can be ambiguous, depending on exactly how its volume is defined, and this may cause confusion in measurement. A common example is sand: if it is gently poured into a container, the density will be low; if the same sand is compacted into the same container, it will occupy less volume and consequently exhibit a greater density. This is because sand, like all powders and granular solids, contains a lot of air space in between individual grains. The density of the material including the air spaces is the bulk density, which differs significantly from the density of an individual grain of sand with no air included.
The Huygens–Fresnel principle [1] (named for Dutch physicist Christiaan Huygens, and French physicist Augustin-Jean Fresnel) is a method of analysis applied to problems of wave propagation (both in the far field limit and in near field diffraction). It recognizes that each point of an advancing wave front is in fact the center of a fresh disturbance and the source of a new train of waves; and that the advancing wave as a whole may be regarded as the sum of all the secondary waves arising from points in the medium already traversed. This view of wave propagation helps better understand a variety of wave phenomena, such as diffraction.
For example, if two rooms are connected by an open doorway and a sound is produced in a remote corner of one of them, a person in the other room will hear the sound as if it originated at the doorway. As far as the second room is concerned, the vibrating air in the doorway is the source of the sound. The same is true of the light passing the edge of an obstacle, but this is not as easily observed because of the short wavelength of visible light.
A common application of Huygens' principle is for the case of a plane wave (usually light, radio waves, x-rays or electrons) incident on an aperture of arbitrary shape. Huygens' principle states that each point in the hole acts as a point source. A point source generates waves that travel spherically in all directions (similar to circular waves caused by dropping small stone in a pond). The sum of the waves from all the point sources at any point beyond the aperture can be calculated by integration or numerical modelling.
Infrasound is sound that is lower in frequency than 20 Hz (Hertz) or cycles per second, the normal limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. The ear is the primary organ for sensing infrasound, but at higher levels it is possible to feel infrasound vibrations in various parts of the body.
The study of such sound waves is sometimes referred to as infrasonics, covering sounds beneath 20 Hz down to 0.001 Hz. This frequency range is utilized for monitoring earthquakes, charting rock and petroleum formations below the earth, and also in ballistocardiography and seismocardiography to study the mechanics of the heart. Infrasound is characterized by an ability to cover long distances and get around obstacles with little dissipation.
Possibly the first observation of naturally occurring infrasound was in the aftermath of the 1883 eruption of Krakatoa, when concussive acoustic waves circled the globe seven times or more and were recorded on barometers worldwide.[citation needed] Infrasound was also used by Allied forces in World War I to locate artillery. One of the pioneers in infrasonic research was French scientist Vladimir Gavreau, born in Russia as Vladimir Gavronsky.[1] His interest in infrasonic waves first came about in his lab during the 1960s, when he and his lab assistants experienced pain in the ear drums and shaking lab equipment, but no audible sound was picked up on his microphones. He concluded it was infrasound and soon got to work preparing tests in the labs. One of his experiments was an infrasonic whistle.
A number of American universities have active research programs in infrasound, including the University of Mississippi, Southern Methodist University, the University of California at San Diego, the University of Alaska Fairbanks, and the University of Hawaii at Manoa.
Infrasound sometimes results naturally from severe weather, surf,[5] lee waves, avalanches, earthquakes, volcanoes, bolides,[6] waterfalls, calving of icebergs, aurora, lightning and upper-atmospheric lightning.[7] Nonlinear ocean wave interactions in ocean storms produce pervasive infrasound vibrations around 0.2 Hz, known as microbaroms.[8] Infrasound can also be generated by man-made processes such as sonic booms and explosions (both chemical and nuclear), by machinery such as diesel engines and older designs of down tower wind turbines and by specially designed mechanical transducers (industrial vibration tables) and large-scale subwoofer loudspeakers.[9] The Comprehensive Nuclear-Test-Ban Treaty Organization uses infrasound as one of its monitoring technologies (along with seismic, hydroacoustic, and atmospheric radionuclide monitoring).
Whales, elephants, hippopotamuses, rhinoceros, giraffes, okapi, and alligators are known to use infrasound to communicate over distances—up to hundreds of miles in the case of whales. It has also been suggested that migrating birds use naturally generated infrasound, from sources such as turbulent airflow over mountain ranges, as a navigational aid.[10] Elephants, in particular, produce infrasound waves that travel through solid ground and are sensed by other herds using their feet, although they may be separated by hundreds of kilometres.
Scientists accidentally discovered that the spinning core or vortex of a tornado creates infrasonic waves. When the vortices are large, the frequencies are lower; smaller vortices have higher, though still infrasonic, frequencies. These low frequency sound waves can be detected for up to 160 kilometres (100 mi) away and can help provide early warning of tornadoes
aNswer ; Accelerator physics deals with the problems of building and operating particle accelerators.
The experiments conducted with particle accelerators are not regarded as part of accelerator physics. These belong (according to the objectives of the experiments) to particle physics, nuclear physics, condensed matter physics, materials physics, etc. as well as to other sciences and technical fields. The types of experiments done at a particular accelerator and/or its other uses are largely constrained by the characteristics of the accelerator itself, such as energy (per particle), types of particles, beam intensity, beam quality, etc.
Accelerator physics itself is the study of the motion of the particle beam through the machine, control and manipulation of the beam, interaction with the machine itself, and measurements of the various parameters associated with particle beams.
Contents [hide] 1 Equations of motion 2 Diagnostics 3 Machine tolerances 4 Interactions between the beam and the machine 5 See also 6 External links
[edit] Equations of motion The motion of charged particles through an accelerator is controlled using applied electro-magnetic fields, and the equations of motion may be derived from (or, since in many cases a general solution is not possible, approximated from) relativistic Hamiltonian mechanics. Typically, a separate Hamiltonian is written down for each element (e.g. for a single quadrupole magnet, or accelerating structure) to allow the equations of motion to be solved for this one element. Once this has been done for each element encountered in the machine, the full trajectory of each particle may be calculated for the entire machine.
In many cases a general solution of the full Hamiltonian is not possible, so it is necessary to make approximations. This may take the form of the Paraxial approximation (a Taylor series in the dynamical variables, truncated to low order), however, even in the cases of strongly non-linear magnetic fields, a Lie transform may be used to construct an integrator with a high degree of accuracy, and the paraxial approximation is not necessary.
[edit] Diagnostics A vital component of any accelerator are the diagnostic devices that allow various properties of the particle bunches to be measured.
A typical machine may use many different types of measurement device in order to measure different properties. These include (but are not limited to) Beam Position Monitors (BPMs) to measure the position of the bunch, screens (fluorescent screens, Optical Transition Radiation (OTR) devices) to image the profile of the bunch, wire-scanners to measure its cross-section, and toroids or ICTs to measure the bunch charge (i.e. the number of particles per bunch).
While many of these devices rely on well understood technology, designing a device capable of measuring a beam for a particular machine is a complex task requiring much expertise. Not only is a full understanding of the physics of the operation of the device necessary, but it is also necessary to ensure that the device is capable of measuring the expected parameters of the machine under consideration.
Success of the full range of beam diagnostics often underpins the success of the machine as a whole.
(often abbreviated E-M radiation or EMR) is a phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It consists of electric and magnetic field components which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. Electromagnetic radiation is classified into several types according to the frequency of its wave; these types include (in order of increasing frequency and decreasing wavelength): radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. A small and somewhat variable window of frequencies is sensed by the eyes of various organisms; this is what is called the visible spectrum, or light. EM radiation carries energy and momentum that may be imparted to matter with which it interacts.
theory:
Electromagnetic waves were first postulated by James Clerk Maxwell and subsequently confirmed by Heinrich Hertz. Maxwell derived a wave form of the electric and magnetic equations, revealing the wave-like nature of electric and magnetic fields, and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave. According to Maxwell's equations, a spatially-varying electric field generates a time-varying magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form an electromagnetic wave. A quantum theory of the interaction between electromagnetic radiation and matter such as electrons is described by the theory of quantum electrodynamics.
Electromagnetism An electromagnet is an object that acts like a magnet, but its magnetic force is created and controlled by electricity—thus the name electromagnet. By wrapping insulated wire around a piece of iron and then running electrical current through the wire, the iron becomes magnetized. This happens because a magnetic field is created around a wire when it has electrical current running through it. Creating a coil of wire concentrates the field. Wrapping the wire around an iron core greatly increases the strength of the magnetic field. Making an electromagnet If you wrap a wire around an iron core, such as a nail, and you send electrical current through the wire, the nail will become highly magnetized. You can verify that by picking up small objects or by showing its effect on a compass. This is called an electromagnet.
Insulated wire Note that the wire must be an insulated wire. A bare wire would cause an electrical short and the current would then run through the nail or metal core. In some electromagnets, like in an electric motor, the wire will look like bare copper, but it is insulated with a thin coating of a clear material. Also, if the wire is thin, it may get warm from the resistance to the electricity passing through it. Turn on and off The most interesting feature of the electromagnet is that when the electrical current is turned off, the magnetism is also turned off. This is especially true if the core is made of soft iron, which quickly loses its magnetism. Hardened steel may retain its magnetism, so you can't use the most valuable feature of an electromagnet. Being able to turn the magnetism on and off has lead to many amazing inventions and applications. How electromagnetism works When electricity passed through a wire, a magnetic field is created around the wire. Looping the wire increases the magnetic field. Adding an iron core greatly increases the effect and creates an electromagnet. You can create an electromagnet without the iron core. That is usually called a solenoid. Magnetic field When DC electricity is passed through a wire, a magnetic field rotates around the wire in a specific direction. Compass can show field Connecting a wire to a battery and placing a compass near the wire can demonstrate a magnetic field. When the current is turned on, the compass-needle will move. If you reverse the direction of the current, the needle will move in the opposite direction. Right hand rule To find the direction the magnetic field is going, you can use the "right-hand rule" to determine it. If you take your right hand and wrap it around the wire, with your thumb pointing in the direction of the electrical current (positive to negative), then your fingers are pointing in the direction of the magnetic field around the wire. Try it with the picture above. Wire in a coil Wrapping the wire in a coil concentrates and increases the magnetic field, because the additive effect of each turn of the wire. A coil of wire used to create a magnetic field is called a solenoid. Iron core Wrapping the wire around an iron core greatly increases the magnetic field. If you put a nail in the coil in the drawing above, it would result in an electromagnet with the a north seeking pole on the "N" side. Using AC electricity If AC electricity is used, the electromagnet has the same properties of a magnet, except that the polarity reverses with the AC cycle. Note that it is not a good idea to try to make an AC electromagnet. This is because of the high voltage in house current. Using a wire around a nail would result in a blown fuse in the AC circuit box. There is also the potential of an electric shock.
The voltage between two (electron) positions "A" and "B", inside a solid electrical conductor (or inside two electrically-connected, solid electrical conductors), is denoted by (VA − VB). This voltage is the electrical driving force that drives a conventional electric current in the direction A to B. Voltage can be directly measured by a voltmeter. Well-constructed, correctly used, real voltmeters approximate very well to ideal voltmeters. An analogy involving the flow of water is sometimes helpful in understanding the concept of voltage (see below).
Precise modern and historic definitions of voltage exist, but (due to the development of the electron theory of metal conduction in the period 1897 to 1933, and to developments in theoretical surface science from about 1910 to about 1950, particularly the theory of local work function) some older definitions are no longer regarded as strictly correct. This is because they neglect the existence of "chemical" effects and surface effects. A particular lesson from surface science is that, to get consistency and universality, formal definitions must relate to positions or (better) electron states inside conductors.
In conduction processes occurring in metals and most other solids, electric currents consist almost exclusively of the flow of electrons in the direction B to A. This movement of electrons is controlled by differences in a so-called "total local thermodynamic potential" often denoted by the symbol µ ("mu"). This parameter is often called the "local Fermi level" or sometimes the "(local) electrochemical potential of an electron" or the "total (local) chemical potential of an electron". The modern electron-based definition of voltage (VA − VB) is in terms of differences in µ:
Currents don't have Voltage............;;; Voltage is not a characteristic of electric current. It's a common mistake to believe that a current "has a voltage" (and this mistake is probably associated with the 'current electricity' misconception, where people believe that 'current' is a kind of substance that flows). Voltage and current are two independent things. It is easy to create a current which lacks a voltage: just short out an electromagnet coil. It is also easy to create a voltage without a current: flashlight batteries maintain their voltage even when they are sitting on the shelf in the store. Water analogy: Think of water pressure without a flow. That's like voltage alone. Now think of water that's coasting along; a water flow without a pressure. That's like electric current alone.
friction forces causes energy loss that has enormous practical importance. it is estimated that in the U.S. Alone, the cost of our imperfect understanding in friction is more than 500 billion dollars.friction which is worse in vacuum, has caused irreversible failures in many space instruments. on the other hand, friction is useful in many instances. without friction we would not able to walk, cars will not moved,and violins would not work.in other cases one wants to maximize friction, like when stopping a train.
the frictional force is also presumed to be proportional to the coefficient of friction. however, the amount of force required to move an object starting from rest it usually its greater than the force required to keep it moving in constant once it is started. therefore the two coefficient are sometimes quoted for a given pair of surface- the coefficient of static friction and a coefficient of kinetic friction. the force expression above can be called the standard model of surface friction and is dependent upon several assumptions about friction.
Momentum of the system does not change value. This allows one to calculate and predict the outinteracting momentum is the product of mass and velocityof an object.It has a formula of p=mv.It is a corner stone concept in physics.With a closed system of objects,the total comes when objects bounce into one another. Or, by knowing the outcome of a collision, one can reason what was the initial state of the system.
When an object is moving, it has a non-zero momentum. If an object is standing still, then its momentum is zero. To calculate the momentum of a moving object multiply the mass of the object times its velocity. The symbol for momentum is a small p.
* EXAMPLE OF MOMENTUM CALCULATION: Find the momentum of an oject that has a mass of 2.0 kg and has a velocity of 4.0 m/s.
m=2.0 kg v=4.0 m/s p=?
p=mv
p=(2.0kg)(4.0m/s)
p=8.0 kg m/s
Momentum is also a vector.That means, that momentum is a quantity that has a magnitude, or size, and a direction. The above problem is a one dimensional problem. That is, the object is moving along a straight line. In situations like this the momentum is usually stated to be positive, to the right, or negative,to the left. So, in the above problem one would say that the momentum is 'positive 8.0 kg-m/s', or '8.0 kg-m/s to the right.' Usually, though, in simple cases like this we just say that the momentum is '8.0 kg-m/s' with the positive sign understood.
Momentum problems can become more complicated, however. Soon, you will be doing momentum problems in two and three dimensions. Under these conditions, say in a two dimensional problem, one would state a momentum using language such as '3.0 kg-m/s in a direction of 50 degrees North of West.'
At first, though, our momentum problems will be in only one dimension. We will imagine objects traveling in a straight line.
Sometimes the concept of momentum is confused with the concept of velocity. Do not do this. Momentum is related to velocity. In fact, they both have the same direction. That is, if an object has a velocity that is aimed toward the right, then its momentum will also be directed to the right. However, momentum is made up of both mass and velocity. One must take the mass and multiply it by the velocity to get the momentum.
Friction is the force resisting the relative lateral ,motion of solid surfaces, or material elements in contact. It is usually subdivided into several varieties:
* Dry friction resists relative lateral motion of two solid surfaces in contact. Dry friction is also subdivided into static friction between non-moving surfaces, and kinetic friction (sometimes called sliding friction or dynamic friction) between moving surfaces.
Dynamics (from Greek δυναμικός - dynamikos "powerful", from δύναμις - dynamis "power") may refer to:
* Dynamics (music), In music, dynamics refers to the softness or loudness of a sound or note. The term is also applied to the written or printed musical notation used to indicate dynamics (also known as volume in a song)
FIELDS
* Analytical dynamics refers to the motion of bodies as induced by external forces * Flight dynamics, the science of aircraft and spacecraft design * Force Dynamics * Fluid dynamics, the study of fluid flow o Computational fluid dynamics * Molecular dynamics, the study of motion on the molecular level o Langevin dynamics + Brownian dynamics * In quantum physics, dynamics may refer to how forces are quantized, as in quantum electrodynamics or quantum chromodynamics * Relativistic dynamics may refer to a combination of relativistic and quantum concepts * Stellar dynamics * System dynamics, the study of the behaviour of complex systems * Thermodynamics, a branch of physics that studies the relationships between heat and mechanical energy
[edit] Branch
* Aerodynamics, the study of gases in motion * Hydrodynamics, the study of liquids in motion * Neurodynamics, an area of research in the brain sciences which places a strong focus upon the spatio-temporal (dynamic) character of neural activity in describing brain function * Thermodynamics
An alpha particle is the same as a helium-4 nucleus, and both mass number and atomic number are the same.
Alpha decay is by far the most common form of cluster decay where the parent atom ejects a defined daughter collection of nucleons, leaving another defined product behind (in nuclear fission, a number of different pairs of daughters of approximately equal size are formed). Alpha decay is the most likely cluster decay because of the combined extremely high binding energy and relatively small mass of the helium-4 product nucleus
Alpha decay, like other cluster decays, is fundamentally a quantum tunneling process. Unlike beta decay, alpha decay is governed by the interplay between the nuclear force and the electromagnetic force.
Alpha decay is a mode of radioactive decay seen only in heavier nuclides, with the lightest known alpha emitter being the lightest isotopes (mass numbers 106–110) of tellurium (element 52).
Archimedes' principle does not consider the surface tension (capillarity) acting on the body.[3]
The weight of the displaced fluid is directly proportional to the volume of the displaced fluid (if the surrounding fluid is of uniform density). Thus, among completely submerged objects with equal masses, objects with greater volume have greater buoyancy.
Suppose a rock's weight is measured as 10 newtons when suspended by a string in a vacuum. Suppose that when the rock is lowered by the string into water, it displaces water of weight 3 newtons. The force it then exerts on the string from which it hangs would be 10 newtons minus the 3 newtons of buoyant force: 10 − 3 = 7 newtons. Buoyancy reduces the apparent weight of objects that have sunk completely to the sea floor. It is generally easier to lift an object up through the water than it is to pull it out of the water.
Assuming Archimedes' principle to be reformulated as follows,
Archimedes' principle does not consider the surface tension (capillarity) acting on the body.[3]
The weight of the displaced fluid is directly proportional to the volume of the displaced fluid (if the surrounding fluid is of uniform density). Thus, among completely submerged objects with equal masses, objects with greater volume have greater buoyancy.
Suppose a rock's weight is measured as 10 newtons when suspended by a string in a vacuum. Suppose that when the rock is lowered by the string into water, it displaces water of weight 3 newtons. The force it then exerts on the string from which it hangs would be 10 newtons minus the 3 newtons of buoyant force: 10 − 3 = 7 newtons. Buoyancy reduces the apparent weight of objects that have sunk completely to the sea floor. It is generally easier to lift an object up through the water than it is to pull it out of the water.
acceleration is the change in velocity over time. Because velocity is a vector, it can change in two ways: a change in magnitude and/or a change in direction. In one dimension, i.e. a line, acceleration is the rate at which something speeds up or slows down. However, as a vector quantity, acceleration is also the rate at which direction change. Acceleration has the dimensions L T−2. In SI units, acceleration is measured in meters per second squared (m/s2).
In common speech, the term acceleration commonly is used for an increase in speed (the magnitude of velocity); a decrease in speed is called deceleration. In physics, a change in the direction of velocity also is an acceleration: for rotary motion, the change in direction of velocity results in centripetal (toward the center) acceleration; where as the rate of change of speed is a tangential acceleration. * Acceleration is a vector quantity which is defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity.
Sports announcers will occasionally say that a person is accelerating if he/she is moving fast. Yet acceleration has nothing to do with going fast. A person can be moving very fast and still not be accelerating. Acceleration has to do with changing how fast an object is moving. If an object is not changing its velocity, then the object is not accelerating. The data at the right are representative of a northward-moving accelerating object. The velocity is changing over the course of time. In fact, the velocity is changing by a constant amount - 10 m/s - in each second of time. Anytime an object's velocity is changing, the object is said to be accelerating; it has an acceleration.Acceleration due to gravity. This type of acceleration is given a special symbol, g. Since acceleration is a vector quantity, it has magnitude (size) and direction. On the surface of the Earth, the freely falling object has the following acceleration: g = -9.80 m/s2. Assuming there is no air resistance, all equations given in this section can be modified to apply to falling object, by simply replacing a with g.
The focal length of an optical system is a measure of how strongly it converges (focuses) or diverges (defocuses) light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus. A system with a shorter focal length has greater optical power than one with a long focal length; that is, it bends the rays more strongly, bringing them to a focus in a shorter distance.
In telescopy and most photography, longer focal length or lower optical power is associated with larger magnification of distant objects, and a narrower angle of view. Conversely, shorter focal length or higher optical power is associated with a wider angle of view. In microscopy, on the other hand, a short objective lens focal length leads to higher magnification.
Pressure is defined as force per unit area. It is usually more convenient to use pressure rather than force to describe the influences upon fluid behavior. The standard unit for pressure is the Pascal, which is a Newton per square meter.
For an object sitting on a surface, the force pressing on the surface is the weight of the object, but in different orientations it might have a different area in contact with the surface and therefore exert a different pressure.
here are many physical situations where pressure is the most important variable. If you are peeling an apple, then pressure is the key variable: if the knife is sharp, then the area of contact is small and you can peel with less force exerted on the blade. If you must get an injection, then pressure is the most important variable in getting the needle through your skin: it is better to have a sharp needle than a dull one since the smaller area of contact implies that less force is required to push the needle through the skin.
Pressure in a fluid may be considered to be a measure of energy per unit volume or energy density. For a force exerted on a fluid, this can be seen from the definition of pressure:
The most obvious application is to the hydrostatic pressure of a fluid, where pressure can be used as energy density alongside kinetic energy density and potential energy density in the Bernoulli equation.
The other side of the coin is that energy densities from other causes can be conveniently expressed as an effective "pressure". For example, the energy density of solvent molecules which leads to osmosis is expressed as osmotic pressure. The energy density which keeps a star from collapsing is expressed as radiation pressure.
beryllium is the chemical element with the symbol Be and atomic number 4.
A bivalent element, beryllium is found naturally only combined with other elements in minerals. Notable gemstones which contain beryllium include beryl (aquamarine, emerald) and chrysoberyl. The free element is a steel-grey, strong, lightweight brittle alkaline earth metal. It is primarily used as a hardening agent in alloys, notably beryllium copper. Structurally, beryllium's very low density (1.85 times that of water), high melting point (1278 °C), high temperature stability, and low coefficient of thermal expansion, make it in many ways an ideal aerospace material, and it has been used in rocket nozzles and is a significant component of planned space telescopes. Because of its relatively high transparency to X-rays and other ionizing radiation types, beryllium also has a number of uses as filters and windows for radiation and particle physics experiments.
Commercial use of beryllium metal presents technical challenges due to the toxicity (especially by inhalation) of beryllium-containing dusts. Beryllium produces a direct corrosive effect to tissue, and can cause a chronic life-threatening allergic disease called berylliosis in susceptible persons.
Beryllium is a relatively rare element in both the Earth and the universe. The element is not known to be necessary or useful for either plant or animal life.
Beryllium was discovered by Louis-Nicolas Vauquelin in 1798 as a component of beryl and in emeralds. Friedrich Wöhler[5] and Antoine Bussy independently isolated the metal in 1828 by reacting potassium and beryllium chloride. Beryllium's chemical similarity to aluminum was probably why beryllium was missed in previous searches
The name beryllium comes (via Latin: Beryllus and French: Béryl) from the Greek βήρυλλος, bērullos, beryl, from Prakrit veruliya (वॆरुलिय), from Pāli veḷuriya (वेलुरिय); veḷiru (भेलिरु) or, viḷar (भिलर्), "to become pale," in reference to the pale semiprecious gemstone beryl.[7] The original source of the word "Beryllium" is the Sanskrit word: वैडूर्य vaidurya-, which is of Dravidian origin and could be derived from the name of the modern city of Belur.[8] For about 160 years, beryllium was also known as glucinum or glucinium (with the accompanying chemical symbol "Gl"[9]), the name coming from the Greek word for sweet: γλυκυς, due to the sweet taste of its salts.
The Ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitations. It was first stated by Émile Clapeyron in 1834 as a combination of Boyle's law and Charles's law.[1] It can also be derived from kinetic theory, as was achieved (apparently independently) by August Krönig in 1856[2] and Rudolf Clausius in 1857.[3] The state of an amount of gas is determined by its pressure, volume, and temperature. The modern form of the equation is:
where p is the absolute pressure of the gas; V is the volume of the gas; n is the amount of substance of the gas, usually measured in moles; R is the gas constant (which is 8.314472 J·K−1·mol−1 in SI units[4]); and T is the absolute temperature. Since the angels it neglects both molecular size and intermolecular attractions, the ideal gas law is most accurate for monatomic gases at high temperatures and low pressures. The neglect of molecular size becomes less important for larger volumes, i.e., for lower pressures. The relative importance of intermolecular attractions diminishes with increasing thermal kinetic energy i.e., with increasing temperatures. More sophisticated equations of state, such as the van der Waals equation, allow deviations from ideality caused by molecular size and intermolecular forces to be taken into account.
Gravitation, or gravity, is a natural phenomenon by which objects with mass attract one another.[1] In everyday life, gravitation is most familiar as the agent that lends weight to objects with mass and causes them to fall to the ground when dropped. Gravitation causes dispersed matter to coalesce, thus accounting for the existence of the Earth, the Sun, and most of the macroscopic objects in the universe. It is responsible for keeping the Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around the Earth; for the formation of tides; for convection, by which fluid flow occurs under the influence of a density gradient and gravity; for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena observed on Earth. Modern physics describes gravitation using the general theory of relativity, in which gravitation is a consequence of the curvature of spacetime which governs the motion of inertial objects. The simpler Newton's law of universal gravitation provides an accurate approximation for most calculations.
Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and early 17th centuries. In his famous (though possibly apocryphal)[2] experiment dropping balls from the Tower of Pisa, and later with careful measurements of balls rolling down inclines, Galileo showed that gravitation accelerates all objects at the same rate. This was a major departure from Aristotle's belief that heavier objects are accelerated faster.[3] Galileo correctly postulated air resistance as the reason that lighter objects may fall more slowly in an atmosphere. Galileo's work set the stage for the formulation of Newton's theory of gravity.
A collision is an isolated event in which two or more moving bodies (colliding bodies) exert relatively strong forces on each other for a relatively short time.
Collisions involve forces (there is a change in velocity). Collisions can be elastic, meaning they conserve energy and momentum, inelastic, meaning they conserve momentum but not energy, or totally inelastic (or plastic), meaning they conserve momentum and the two objects stick together.
Elastic and Inelastic Collisions
A perfectly elastic collision is defined as one in which there is no loss of kinetic energy in the collision. An inelastic collision is one in which part of the kinetic energy is changed to some other form of energy in the collision. Any macroscopic collision between objects will convert some of the kinetic energy into internal energy and other forms of energy, so no large scale impacts are perfectly elastic. Momentum is conserved in inelastic collisions, but one cannot track the kinetic energy through the collision since some of it is converted to other forms of energy. Collisions in ideal gases approach perfectly elastic collisions, as do scattering interactions of sub-atomic particles which are deflected by the electromagnetic force. Some large-scale interactions like the slingshot type gravitational interactions between satellites and planets are perfectly elastic. Collisions between hard spheres may be nearly elastic, so it is useful to calculate the limiting case of an elastic collision. The assumption of conservation of momentum as well as the conservation of kinetic energy makes possible the calculation of the final velocities in two-body collisions.
AMPERE The ampere was originally defined as one tenth of the CGS system electromagnetic unit of current (now known as the abampere), the amount of current which generates a force of two dynes per centimetre of length between two wires one centimetre apart. The size of the unit was chosen so that the units derived from it in the MKSA system would be conveniently sized.
The "international ampere" was an early realization of the ampere, defined as the current that would deposit 0.001118000 grams of silver per second from a silver nitrate solution.[10] Later, more accurate measurements revealed that this current is 0.99985 A.
The ampere (symbol: A) is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics. In practice, its name is often shortened to amp.
In practical terms, the ampere is a measure of the amount of electric charge passing a point per unit time. Around 6.242 × 1018 electrons passing a given point each second constitutes one ampere. (Since electrons have negative charge, they flow in the opposite direction to the conventional current.)
Ampère's force law states that there is an attractive force between two parallel wires carrying an electric current. This force is used in the formal definition of the ampere which states that it is the constant current which will produce an attractive force of 2 × 10–7 newtons per metre of length between two straight, parallel conductors of infinite length and negligible circular cross section placed one metre apart in a vacuum.
In physics, velocity is the rate of change of position. It is a vector physical quantity; both speed and direction are required to define it. In the SI (metric) system, it is measured in meters per second: (m/s) or ms−1. The scalar absolute value (magnitude) of velocity is speed. For example, "5 meters per second" is a scalar and not a vector, whereas "5 meters per second east" is a vector. The average velocity v of an object moving through a displacement (Δx) during a time interval (Δt) is described by the formula:
The rate of change of velocity is acceleration – how an object's speed or direction changes over time, and how it is changing at a particular point in time. VELOCITY...... Quantity that designates the speed and direction in which a body moves. It can be represented graphically by an arrow (pointing in the direction of the motion), the length of which is proportional to the magnitude, or speed. For an object in circular motion, the direction at any instant is tangential to the circle at that point, and so is perpendicular to the radius at that point. The instantaneous speed of a vehicle, such as an automobile, can be determined by a speedometer, or mathematically by differential calculus. The average speed is the ratio of the distance traveled in any given time interval divided by the time taken.
Archimedes’ principle
ReplyDeleteARCHIMEDES, a Greek philosopher, studied about buoyancy. According to a legend, Archimedes was asked by king Hieron of Syracuse to determine whether his crown was made of pure gold or mixed with a less expensive metal. Thos was so big task for Archimedes that he was thinking of it all the time. He found the answer while he was taking a bath in the tub. Because of his great excitement, he ran in the streets shouting “EUREKA” , a great word meaning of “I found it”. He performed experiments and calculations and came up with what is now called “ARCHIMEDES PRINCIPLE”
“The buoyant force of fluid on an object is equal to the weight of fluid the object is displaces”.
Archimedes’ principle applies to object that sink or float. An object sinks if its weight is greater than the buoyant force, however, it floats if its weight is less than buoyant force.
Teddy mark Flores: Topic>>Force!!
ReplyDeleteTOPIC: Alpha particle
ReplyDelete-(named after and denoted by the first letter in the Greek alphabet, α)
-it consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is produced in the process of alpha decay.
When an atom emits an alpha particle, the atom's mass number decreases by four due to the loss of the four nucleons in the alpha particle. The atomic number of the atom goes down by exactly two, as a result of the loss of two protons – the atom becomes a new element.
Examples: when uranium becomes thorium, or radium becomes radon gas due to alpha decay.
Alpha particles are commonly emitted by all of the larger radioactive nuclei such as uranium, thorium, actinium, and radium, as well as the transuranic elements. Unlike other types of decay, alpha decay as a process must have a minimum-size atomic nucleus which can support it. The smallest nuclei which have to date been found to be capable of alpha emission are the lightest nuclides of tellurium (element 52), with mass numbers between 106 and 110. The process of emitting an alpha sometimes leaves the nucleus in an excited state, with the emission of a gamma ray removing the excess energy.
Energetic helium nuclei may be produced by cyclotrons, synchrotrons, and other particle accelerators, but they are not normally referred to as alpha particles. As noted, helium nuclei may participate in nuclear reactions in stars, and occasionally and historically these have been referred to, as alpha reactons (see triple alpha process.)
Because of the short range of absorption, alphas are not generally dangerous to life unless the source is ingested or inhaled, in which case, they become extremely dangerous. Because of this high mass and strong absorption, if alpha emitting radionuclides do enter the body (if the radioactive material has been inhaled or ingested), alpha radiation is the most destructive form of ionizing radiation. It is the most strongly ionizing, and with large enough doses can cause any or all of the symptoms of radiation poisoning. It is estimated that chromosome damage from alpha particles is about 100 times greater than that caused by an equivalent amount of other radiation. The powerful alpha emitter polonium-210 (a milligram of 210Po emits as many alpha particles per second as 4.215 grams of 226Ra) is suspected of playing a role in lung cancer and bladder cancer related to tobacco smoking.[4] 210Po was used to kill Russian dissident and ex-FSB officer Alexander V. Litvinenko in 2006.[5]
Not only do alphas themselves cause damage, but approximately equal ionization is caused by the recoiling nucleus after alpha emission, and this energy may in turn be especially damaging to genetic material, since the positive cations of many soluble transuranic elements which emit alphas, are chemically attracted to the net negative charge of DNA, causing the recoiling atomic nucleus to be in close proximation to the DNA.
by:jenyleen ayon-ayon :)
Protons Electrons and Neutrons
ReplyDeleteWhat are protons, neutrons and electrons?
Everything around us- air, water, sand, stone, wood, plants, animals, humans- scientists call them all matter.
When we analyze the structure of matter, we see that all matter is made essentially of about a hundred pure substances called elements in different combinations. Some elements do not combine with others and stay in pure form. But in most cases, two or more elements combine to form different substances. These combined substances are called compounds.
For example, the water we drink is a compound of two elements- hydrogen and oxygen. Our common table salt is nothing but a compound of the elements sodium and chlorine. But beware, sugar is a little more complicated - it has carbon in addition to hydrogen and oxygen! Many substances around us, especially the things that make up plant and animal matter, are far more complicated.
But the fact remains- complicated or simple, all matter is made up of elements. Each element is unique- it has its own special qualities. When you break up these elements into smaller and smaller pieces, you will finally get a tiny speck called an atom. Atom is the limit- you cannot break up the atom of an element and expect to see that element’s special qualities continued.
For a long time scientists believed that it is not possible to break up an atom. However some great scientists like J.J. Thomson, Goldstein and Chadwick later discovered that atoms are made up of three particles called Protons, Neutrons and Electrons. These particles are today called sub-atomic particles.
Protons, neutrons and electrons are very tiny particles. They are many times smaller than the smallest speck we can see with our naked eyes. The weight of a proton is somewhat close to the weight of a hydrogen atom, which is the smallest of all atoms. The weight of a neutron is almost the same as a proton. If you divide the weight of a hydrogen atom by 1837, you will get the weight of an electron. Thus electron is the lightest of the subatomic particles.
Of these three particles, protons and electrons have electrical charge on them. Each proton has one unit positive charge on it. Each electron holds one unit of negative charge. Neutrons are not charged particles. The number of protons and electrons in an atom is equal, so they cancel out each other and thus the atom does not have electrical charge on it.
When we speak of things like weight in our everyday life, we use units like grams and kilograms to measure them. We talk of electricity in terms of amperes and watts. However the world of protons, neutrons and electrons is so small we cannot use these units to show their weight or electric charge. Scientists use special units to talk about them.
Protons and neutrons always stay together at the centre of an atom. This part is called the nucleus. The electrons go on circling around the nucleus at very high speeds through special tracks called orbits. This might remind you of our solar system where the planets go on orbiting the sun. Well, the picture is pretty similar except that one is very huge and the other is very tiny.
We found that each atom is made of protons, electrons and neutrons. The atoms of each element have a different number of protons and electrons. No two different elements can have the same number of protons and electrons in their atoms. Hydrogen has one proton and electron in its atom and helium has two protons and electrons in its atom. Oxygen has eight protons and electrons in its atom. Thus it is the number of protons and electrons in the atom that makes each element unique. Scientists explain each element’s behavior using the number of protons, electrons and neutrons it has.
We found earlier that all matter is made up of atoms. Now that we know of protons, neutrons and electrons, we can modify our statement. All matter, everything we see around us, is made up of protons, neutrons and electrons!
POTENCIAL ENERGY
ReplyDeletePotential energy is energy that is stored within a system. It exists when there is a force that tends to pull an object back towards some lower energy position. This force is often called a restoring force. For example, when a spring is stretched to the left, it exerts a force to the right so as to return to its original, unstretched position. Similarly, when a mass is lifted up, the force of gravity will act so as to bring it back down. The initial action of stretching the spring or lifting the mass both require energy to perform. The energy that went into lifting up the mass is stored in its position in the gravitational field, while similarly, the energy it took to stretch the spring is stored in the metal. According to the principle of conservation of energy, energy cannot be created or destroyed; hence this energy cannot disappear. Instead, it is stored as potential energy. If the spring is released or the mass is dropped, this stored energy will be converted into kinetic energy by the restoring force, which is elasticity in the case of the spring, and gravity in the case of the mass. Think of a roller coaster. When the coaster climbs a hill it has potential energy. At the very top of the hill is its maximum potential energy. When the car speeds down the hill potential energy turns into kinetic. Kinetic energy is greatest at the bottom.
The more formal definition is that potential energy is the energy difference between the energy of object in a given position and its energy at a reference position.
There are various types of potential energy, each associated with a particular type of force. More specifically, every conservative force gives rise to potential energy. For example, the work of an elastic force is called elastic potential energy; work of the gravitational force is called gravitational potential energy; work of the Coulomb force is called electric potential energy; work of the strong nuclear force or weak nuclear force acting on the baryon charge is called nuclear potential energy; work of intermolecular forces is called intermolecular potential energy. Chemical potential energy, such as the energy stored in fossil fuels, is the work of the Coulomb force during rearrangement of mutual positions of electrons and nuclei in atoms and molecules. Thermal energy usually has two components: the kinetic energy of random motions of particles and the potential energy of their mutual positions.
This comment has been removed by the author.
ReplyDeleteDENSITY is a physical property of matter, as each element and compound has a unique density associated with it. Density defined in a qualitative manner as the measure of the relative "heaviness" of objects with a constant volume.
ReplyDeleteFor example: A rock is obviously more dense than a crumpled piece of paper of the same size.
A styrofoam cup is less dense than a ceramic cup.
Density may also refer to how closely "packed" or "crowded" the material appears to be - again refer to the styrofoam vs. ceramic cup.
Density Comparison to Water: In chemistry, the density of many substances is compared to the density of water. Does an object float on water or sink in the water? If an object such as a piece of wood floats on water it is less dense than water vs. if a rock sinks, it is more dense than water.
Density examples:
Oil and vinegar salad dressing: The oil floats on the vinegar water mixture, while the solids sink to the bottom.
Oil spills: What happens when an oil tanker leaks on the ocean? The oil floats on the water since it is less dense, and this provides some opportunity to clean up the oil spills by skimming the oil from the surface of the water.
Ice: Everyone knows that ice floats on water, but did you know that this is an abnormal physical property of solid/liquid state of water? The more normal physical property is for the solid of a compound to sink in its own liquid.
Demonstrations with Density
Mysterious Ice
Layers of Liquids
Egg Densities - sugar water/oil
Smart Eggs - salt water and acid
Floating Eggs - sugar and water
Floating Spheres
Lava Lamp
Underwater Smoke Stack
Floating objects in water
Mathematical Definition of Density
The formal definition of density is mass per unit volume. Usually the density is expressed in grams per mL or cc. Mathematically a "per" statement is translated as a division. cc is a cubic centimeter and is equal to a mL Therefore,
Density = mass/volume = g/mL
In order to determine the density of an object, it is necessary to know: the mass, the volume of the substance, and the definition of density.
Density = mass (g)
volume (mL)
Mass vs. Weight: Although the terms mass and weight are used almost interchangeably, there is a difference between them. Mass is a measure of the quantity of matter, which is constant all over the universe. Weight is proportional to mass but depends on location in the universe. Weight is the force exerted on a body by gravitational attraction (usually by the earth).
Example: The mass of a man is constant. However the man may weigh: 150 lbs on earth, 25 lbs on the moon (because the force of gravity on the moon is 1/6 that of the earth), and be "weightless" in space.
Magnetic Monopole
ReplyDeleteA magnetic monopole is a hypothetical physics particle with only one magnetic pole.
Normally, magnets have two "charges" - a north pole and a south pole - which mean that, overall, the magnetic charge of the magnet cancels out.
Magnetic monopoles, on the other hand, behave more like electrical charge, which have a net positive or negative charge.
Magnetic monopoles were originally proposed by Pierre Curie. Paul Dirac developed a quantum physical theory of monopoles in 1931. Since electrical charges are quantized, Dirac was able to show that the existence of magnetic monopoles is consistent with existing laws of physics.
Many current theories (such as string theory) in physics predict that in the high energy state of the early universe, shortly after the big bang, magnetic monopoles would have existed in nature. If these theories are correct, it would take more powerful particle accelerators to generate the magnetic monopoles.
In addition, it is possible to create effective magnetic monopoles within certain types of materials, so that the north and south poles move freely within the material, instead of in coupled pairs.
This comment has been removed by the author.
ReplyDeleteYOUNG'S EXPERIMENT
ReplyDeleteYoung's experiment) demonstrates the inseparability of the wave and particle natures of light and other quantum particles. A coherent light source illuminates a thin plate with two parallel slits cut in it, and the light passing through the slits strikes a screen behind them. The wave nature of light causes the light waves passing through both slits to interfere, creating an interference pattern of bright and dark bands on the screen. However, at the screen, the light is always found to be absorbed as though it were made of discrete particles, called photons.
If the light travels from the source to the screen as particles, then on the basis of a classical reasoning the number that strike any particular point on the screen is expected to be equal to the sum of those that go through the left slit and those that go through the right slit. In other words, according to classical particle physics the brightness at any point should be the sum of the brightness when the right slit is blocked and the brightness when the left slit is blocked. However, it is found that unblocking both slits makes some points on the screen brighter, and other points darker. This can only be explained by the alternately additive and subtractive interference of waves, not the exclusively additive nature of particles, so we know that light must have some particle-wave duality.
Any modification of the apparatus that can determine which slit a photon passes through destroys the interference pattern, illustrating the complementarity principle; that the light can demonstrate both particle and wave characteristics, but not both at the same time. However, an experiment performed in 1987 produced results that demonstrated that which-path information could be obtained without destroying the possibility of interference. This showed the effect of measurements that disturbed the particles in transit to a lesser degree and thereby influenced the interference pattern only to a comparable extent.
The double slit experiment can also be performed (using different apparatus) with particles of matter such as electrons with the same results, demonstrating that they also show particle-wave duality.
Carbon footprint
ReplyDeleteA Carbon footprint is the amount of greenhouse gas emissions caused by an indidual, organization, or event,
an individual, nation or organization carbon.
This carbon footprint came from the humans activities on there environment and in terms of greenhouse gases produced,
measured in units of carbon dioxide.''
if you will calculate the measure of carbon footprint i think this is just the right time, hoping its not too late,
to take a clear and determined look just responsible to keep this planet liveable for the generation to come?
and also can measured the particular climate changed the carbon footprint can be relates to the amount of
greenhouse gases that produced in our day to day lives though its burning fossil
fuel for elecricity heating and transportation.
The carbon footprint is a measurement of all greenhouse gases we individually produce and has unit
of tonnes ( or kg) of carbon dioxide equivalent.
Evidence of global warming
cause of greenhouse effect and carbon footprint by measuring it.
global warming is the same given by scientist for the gradual increase in temperature of the earth's surface that has
worsened since the industrial revolution.
as the years goes by the measured and amount of pullution getting
bigger and larger. the evidence considerable exists the most of this warming that caused by human activities the effects of the enlargement of the pollution.
this are the altrede chemical composition from the atmosphere.
the pollution give by car's
even the perfume, alcohol, pestiside, methane and nitrous oxide etc.
this are the only example of air pollution.
that calculate by carboon footprint
many questions has there no answer's?
many people are still hoping for a better lifestyle?
what if we do nothing?
what if we do nothing??????
people always saying..
if we could do nothing to the global warming it will rise temperature
that will cause sea level and local climate conditions .
if this will be happened the forests, crop yeilds, water supplies
and also affects human helath, animals, and many types in ecosystem.
The total amount of greenhouse gases produced to directly and indirectly support human activities, usually expressed in equivalent tons of carbon dioxide (CO2).
In other words When you drive a car, the engine burns fuel which creates a certain amount of CO2, depending on its fuel consumption and the driving distance. (CO2 is the chemical symbol for carbon dioxide). When you heat your house with oil, gas or coal, then you also generate CO2. Even if you heat your house with electricity, the generation of the electrical power may also have emitted a certain amount of CO2. When you buy food and goods, the production of the food and goods also emitted some quantities of CO2.
The attached Excel sheet can be used to calculate both CO2 emissions as well as primary energy requirements for the following activities:
*Heating with oil,
*coal,
*wood,
*solar energy or heat pumps
*Electricity consumption.
The actual mix of power generation (coal, oil, natural gas, wood, nuclear energy, hydro energy, solar energy, wind, geothermal or waste) is taken into consideration.
Travelling by car for diesel and petrol fuelled cars. Either by actual fuel consumption or by distance and average fuel consumption.
*Travelling by bus (kilometres or miles)
*Travelling by train (kilometres or miles)
..... we need to save the world.....
..... for the safetiness of all....
by: fatima cordenete :)
MAGNETISM...
ReplyDeleteThe term magnetism is used to describe how materials respond on the microscopic level to an applied magnetic field; to categorize the magnetic phase of a material. For example, the most well known form of magnetism is ferromagnetism such that some ferromagnetic materials produce their own persistent magnetic field. However, all materials are influenced to greater or lesser degree by the presence of a magnetic field. Some are attracted to a magnetic field (paramagnetism); others are repulsed by a magnetic field (diamagnetism); others have a much more complex relationship with an applied magnetic field. Substances that are negligibly affected by magnetic fields are known as non-magnetic substances. They include copper, aluminium, water, and gases.
The magnetic state (or phase) of a material depends on temperature (and other variables such as pressure and applied magnetic field) so that a material may exhibit more than one form of magnetism depending on its temperature, etc.
SOURCES OF MAGNETISM...
There exists a close connection between angular momentum and magnetism, expressed on a macroscopic scale in the Einstein-de Haas effect "rotation by magnetization" and its inverse, the Barnett effect or "magnetization by rotation".
At the atomic and sub-atomic scales, this connection is expressed by the ratio of magnetic moment to angular momentum, the gyromagnetic ratio.
Magnetism, at its root, arises from two sources:
* Electric currents or more generally, moving electric charges create magnetic fields (see Maxwell's Equations).
* Many particles have nonzero "intrinsic" (or "spin") magnetic moments. (Just as each particle, by its nature, has a certain mass and charge, each has a certain magnetic moment, possibly zero.)
In magnetic materials, sources of magnetization are the electrons' orbital angular motion around the nucleus, and the electrons' intrinsic magnetic moment (see Electron magnetic dipole moment). The other potential sources of magnetism are the nuclear magnetic moments of the nuclei in the material which are typically thousands of times smaller than the electrons' magnetic moments, so they are negligible in the context of the magnetization of materials. (Nuclear magnetic moments are important in other contexts, particularly in Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI).)
Ordinarily, the countless electrons in a material are arranged such that their magnetic moments (both orbital and intrinsic) cancel out. This is due, to some extent, to electrons combining into pairs with opposite intrinsic magnetic moments (as a result of the Pauli exclusion principle; see Electron configuration), or combining into "filled subshells" with zero net orbital motion; in both cases, the electron arrangement is so as to exactly cancel the magnetic moments from each electron. Moreover, even when the electron configuration is such that there are unpaired electrons and/or non-filled subshells, it is often the case that the various electrons in the solid will contribute magnetic moments that point in different, random directions, so that the material will not be magnetic.
However, sometimes (either spontaneously, or owing to an applied external magnetic field) each of the electron magnetic moments will be, on average, lined up. Then the material can produce a net total magnetic field, which can potentially be quite strong.
The magnetic behavior of a material depends on its structure (particularly its electron configuration, for the reasons mentioned above), and also on the temperature (at high temperatures, random thermal motion makes it more difficult for the electrons to maintain alignment).
RELATED TOPICS...
ReplyDeleteDIAMAGNETISM...
Diamagnetism appears in all materials, and is the tendency of a material to oppose an applied magnetic field, and therefore, to be repelled by a magnetic field. However, in a material with paramagnetic properties (that is, with a tendency to enhance an external magnetic field), the paramagnetic behavior dominates.[9] Thus, despite its universal occurrence, diamagnetic behavior is observed only in a purely diamagnetic material. In a diamagnetic material, there are no unpaired electrons, so the intrinsic electron magnetic moments cannot produce any bulk effect. In these cases, the magnetization arises from the electrons' orbital motions, which can be understood classically as follows:
When a material is put in a magnetic field, the electrons circling the nucleus will experience, in addition to their Coulomb attraction to the nucleus, a Lorentz force from the magnetic field. Depending on which direction the electron is orbiting, this force may increase the centripetal force on the electrons, pulling them in towards the nucleus, or it may decrease the force, pulling them away from the nucleus. This effect systematically increases the orbital magnetic moments that were aligned opposite the field, and decreases the ones aligned parallel to the field (in accordance with Lenz's law). This results in a small bulk magnetic moment, with an opposite direction to the applied field.
Note that this description is meant only as an heuristic; a proper understanding requires a quantum-mechanical description.
Note that all materials undergo this orbital response. However, in paramagnetic and ferromagnetic substances, the diamagnetic effect is overwhelmed by the much stronger effects caused by the unpaired electrons.
PARAMAGNETISM...
In a paramagnetic material there are unpaired electrons, i.e. atomic or molecular orbitals with exactly one electron in them. While paired electrons are required by the Pauli exclusion principle to have their intrinsic ('spin') magnetic moments pointing in opposite directions, causing their magnetic fields to cancel out, an unpaired electron is free to align its magnetic moment in any direction. When an external magnetic field is applied, these magnetic moments will tend to align themselves in the same direction as the applied field, thus reinforcing it.
FERROMAGNETISM...
A ferromagnet, like a paramagnetic substance, has unpaired electrons. However, in addition to the electrons' intrinsic magnetic moments tendency to be parallel to an applied field, there is also in these materials a tendency for these magnetic moments to orient parallel to each other to maintain a lowered energy state. Thus, even when the applied field is removed, the electrons in the material maintain a parallel orientation.
Every ferromagnetic substance has its own individual temperature, called the Curie temperature, or Curie point, above which it loses its ferromagnetic properties. This is because the thermal tendency to disorder overwhelms the energy-lowering due to ferromagnetic order.
Some well-known ferromagnetic materials that exhibit easily detectable magnetic properties (to form magnets) are nickel, iron, cobalt, gadolinium and their alloys.
MAGNETIC DOMAINS...
ReplyDeleteThe magnetic moment of atoms in a ferromagnetic material cause them to behave something like tiny permanent magnets. They stick together and align themselves into small regions of more or less uniform alignment called magnetic domains or Weiss domains. Magnetic domains can be observed with a magnetic force microscope to reveal magnetic domain boundaries that resemble white lines in the sketch.There are many scientific experiments that can physically show magnetic fields.
Effect of a magnet on the domains.
When a domain contains too many molecules, it becomes unstable and divides into two domains aligned in opposite directions so that they stick together more stably as shown at the right.
When exposed to a magnetic field, the domain boundaries move so that the domains aligned with the magnetic field grow and dominate the structure as shown at the left. When the magnetizing field is removed, the domains may not return to an unmagnetized state. This results in the ferromagnetic material's being magnetized, forming a permanent magnet.
When magnetized strongly enough that the prevailing domain overruns all others to result in only one single domain, the material is magnetically saturated. When a magnetized ferromagnetic material is heated to the Curie point temperature, the molecules are agitated to the point that the magnetic domains lose the organization and the magnetic properties they cause cease. When the material is cooled, this domain alignment structure spontaneously returns, in a manner roughly analogous to how a liquid can freeze into a crystalline solid.
ANTIFERROMAGNETISM...
In an antiferromagnet, unlike a ferromagnet, there is a tendency for the intrinsic magnetic moments of neighboring valence electrons to point in opposite directions. When all atoms are arranged in a substance so that each neighbor is 'anti-aligned', the substance is antiferromagnetic. Antiferromagnets have a zero net magnetic moment, meaning no field is produced by them. Antiferromagnets are less common compared to the other types of behaviors, and are mostly observed at low temperatures. In varying temperatures, antiferromagnets can be seen to exhibit diamagnetic and ferrimagnetic properties.
In some materials, neighboring electrons want to point in opposite directions, but there is no geometrical arrangement in which each pair of neighbors is anti-aligned. This is called a spin glass, and is an example of geometrical frustration.
FERRIMAGNETISM...
Like ferromagnetism, ferrimagnets retain their magnetization in the absence of a field. However, like antiferromagnets, neighboring pairs of electron spins like to point in opposite directions. These two properties are not contradictory, because in the optimal geometrical arrangement, there is more magnetic moment from the sublattice of electrons that point in one direction, than from the sublattice that points in the opposite direction.
The first discovered magnetic substance, magnetite, was originally believed to be a ferromagnet; Louis Néel disproved this, however, with the discovery of ferrimagnetism.
(^_^)
.... topic??
ReplyDelete>>Electromagnetism
-->is the physics of electromagnetic field,a field that exerts a force on charged particles and is reciprocally affected by the presence and motion of such particles..
...a changing magnetic field produces an electric field(this is the phenomenon of electromagnetic induction the basis of operation for electrical generators,induction motors and transformers)Similarly a changing electric field generates a magnetic field.
...The magnetic field is produce by the motion of electrical charges.Thee magnetic field causes the magnetic force associated with magnets.
...The theoritical implication of electromagnetism led to the development of special relativity by Albert Einstein in 1905 and from this is was shown the magnetic fields and electric fields are convertible with relative motion as a four vector
TOPIC
ReplyDeleteDENSITY!!!!!
...For humans, population density is the number of people per unit of area usually per square kilometer or mile (which may include or exclude cultivated or potentially productive area).
... Commonly this may be calculated for a county, city, country, another territory, or the entire world.
...The world population is 6.8 billion [1], and Earth's area is 510 million square kilometers (197 million square miles) [2] . Therefore the worldwide human population density is 6.8 billion ÷ 510 million = 13.1 per km² (34.0 per sq. mile), or 44.7 per km² (115.5 per sq. miles) if only the Earth's land area of 150 million km² (58 million sq. miles) is taken into account. This density rises when the population grows. It also includes all continental and island land area, including Antarctica.
...Considering that over half of the Earth's land mass consists of areas inhospitable to human inhabitation, such as deserts and high mountains, and that population tends to cluster around seaports and fresh water sources, this number by itself does not give any meaningful measurement of human population density.
...Several of the most densely-populated territories in the world are city-states, microstates, micronations, or dependencies. These territories share a relatively small area and a high urbanization level, with an economically specialized city population drawing also on rural resources outside the area, illustrating the difference between high population density and overpopulation.
...Cities with high population densities are, by some, considered to be overpopulated, though the extent to which this is the case depends on factors like quality of housing and infrastructure or access to resources. Most of the most densely-populated cities are in southern and eastern Asia, though Cairo and Lagos in Africa also fall into this category.
..City population is, however, heavily dependent on the definition of "urban area" used: densities are often higher for the central municipality itself, than when more recently-developed and administratively unincorporated suburban communities are included, as in the concepts of agglomeration or metropolitan area, the latter including sometimes neighboring cities. For instance, Milwaukee has a greater population density when just the inner city is measured, and not the surrounding suburbs as well.
this is the formula!!!!!^_^v
Mathematically:
\rho = \frac{m}{V} \,
where:
ρ (rho) is the density,
m is the mass,
V is the volume.
...Different materials usually have different densities, so density is an important concept regarding buoyancy, metal purity and packaging.
...In some cases density is expressed as the dimensionless quantities specific gravity (SG) or relative density (RD), in which case it is expressed in multiples of the density of some other standard material, usually water or air/gas.
AND THAT`S ALL!!! THANK YOU!!!
TOPIC>>DIODE
ReplyDeleteIn electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. The term usually refers to a semiconductor diode, the most common type today, which is a crystal of semiconductor connected to two electrical terminals, a P-N junction. A vacuum tube diode, now little used, is a vacuum tube with two electrodes; a plate and a cathode.
The most common function of a diode is to allow an electric current in one direction (called the diode's forward direction) while blocking current in the opposite direction (the reverse direction). Thus, the diode can be thought of as an electronic version of a check valve. This unidirectional behavior is called rectification, and is used to convert alternating current to direct current, and remove modulation from radio signals in radio receivers.
However, diodes can have more complicated behavior than this simple on-off action, due to their complex non-linear electrical characteristics, which can be tailored by varying the construction of their P-N junction. These are exploited in special purpose diodes that perform many different functions. Diodes are used to regulate voltage (Zener diodes), electronically tune radio and TV receivers (varactor diodes), generate radio frequency oscillations (tunnel diodes), and produce light (light emitting diodes).
SUBMITTED BY: DEXTER a.k.a †♠Red Tearz 03♠†
ZONE MELTING
ReplyDeleteZone melting or zone refining or floating zone process) is a group of similar methods of purifying crystals, in which a narrow region of a crystal is molten, and this molten zone is moved along the crystal (in practice, the crystal is pulled through the heater). The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot. The impurities concentrate in the melt, and are moved to one end of the ingot. Zone refining was developed by William Gardner Pfann in Bell Labs as a method to prepare high purity materials for manufacturing transistors. Its early use was on germanium for this purpose, but it can be extended to virtually any solute-solvent system having an appreciable concentration difference between solid and liquid phases at equilibrium [1]. This process is also known as the float zone process, particularly in semiconductor materials processing.
Another related process is zone remelting, in which two solutes are distributed through a pure metal. This is important in the manufacture of semiconductors, where two solutes of opposite conductivity type are used. For example, in germanium, pentavalent elements of group V such as antimony and arsenic produce negative (n-type) conduction and the trivalent elements of group III such as aluminum and boron produce positive (p-type) conduction. By melting a portion of such an ingot and slowly refreezing it, solutes in the molten region become distributed to form the desired n-p and p-n junctions.
ryan s. zapata
ABBERATION....
ReplyDeleteAberrations are departures of the performance of an optical system from the predictions of paraxial optics.[1] Aberration leads to blurring of the image produced by an image-forming optical system. It occurs when light from one point of an object after transmission through the system does not converge into (or does not diverge from) a single point. Instrument-makers need to correct optical systems to compensate for aberration. The articles on reflection, refraction and caustics discuss the general features of reflected and refracted rays.
Aberration is something that deviates from the normal way but has several specifically defined meanings:
* Optical aberration, an imperfection in image formation by an optical system
* Spherical aberration, which occurs when light rays strike a lens or mirror near its edge
* Chromatic aberration, caused by differences in refractive index for different wavelengths of light
* Defocus aberration, which occurs when a system is out of focus
RELATED TOPIC...
ReplyDeleteABBERATION OF LIGHT...
The aberration of light (also referred to as astronomical aberration or stellar aberration) is an astronomical phenomenon which produces an apparent motion of celestial objects about their real locations. It was discovered and later explained by the third Astronomer Royal, James Bradley, in 1725, who attributed it to the finite speed of light and the motion of Earth in its orbit around the Sun.
At the instant of any observation of an object, the apparent position of the object is displaced from its true position by an amount which depends solely upon the transverse component of the velocity of the observer, with respect to the vector of the incoming beam of light (i.e., the line actually taken by the light on its path to the observer). The result is a tilting of the direction of the incoming light which is independent of the distance between object and observer.
In the case of an observer on Earth, the direction of a star's velocity varies during the year as Earth revolves around the Sun (or strictly speaking, the barycenter of the solar system), and this in turn causes the apparent position of the star to vary. This particular effect is known as annual aberration or stellar aberration, because it causes the apparent position of a star to vary periodically over the course of a year. The maximum amount of the aberrational displacement of a star is approximately 20 arcseconds in right ascension or declination. Although this is a relatively small value, it was well within the observational capability of the instruments available in the early eighteenth century.
Aberration should not be confused with stellar parallax, although it was an initially fruitless search for parallax that first led to its discovery. Parallax is caused by a change in the position of the observer looking at a relatively nearby object, as measured against more distant objects, and is therefore dependent upon the distance between the observer and the object.
In contrast, stellar aberration is independent of the distance of a celestial object from the observer, and depends only on the observer's instantaneous transverse velocity with respect to the incoming light beam, at the moment of observation. The light beam from a distant object cannot itself have any transverse velocity component, or it could not (by definition) be seen by the observer, since it would miss the observer. Thus, any transverse velocity of the emitting source plays no part in aberration. Another way to state this is that the emitting object may have a transverse velocity with respect to the observer, but any light beam emitted from it which reaches the observer, cannot, for it must have been previously emitted in such a direction that its transverse component has been "corrected" for. Such a beam must come "straight" to the observer along a line which connects the observer with the position of the object when it emitted the light.
Aberration should also be distinguished from light-time correction, which is due to the motion of the observed object, like a planet, through space during the time taken by its light to reach an observer on Earth. Light-time correction depends upon the velocity and distance of the emitting object during the time it takes for its light to travel to Earth. Light-time correction does not depend on the motion of the Earth—it only depends on Earth's position at the instant when the light is observed. Aberration is usually larger than a planet's light-time correction except when the planet is near quadrature (90° from the Sun), where aberration drops to zero because then the Earth is directly approaching or receding from the planet. At opposition to or conjunction with the Sun, aberration is 20.5" while light-time correction varies from 4" for Mercury to 0.37" for Neptune (the Sun's light-time correction is less than 0.03").
DIFFRACTION
ReplyDeleterefers to various phenomena which occur when a wave encounters an obstacle.
It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Similar effects are observed when light waves travel through a medium with a varying refractive index or a sound wave through one with varying acoustic impedance. Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, x-rays and radio waves. As physical objects have wave-like properties (at the atomic level), diffraction also occurs with matter and can be studied according to the principles of quantum mechanics.
While diffraction occurs whenever propagating waves encounter such changes, its effects are generally most pronounced for waves where the wavelength is on the order of the size of the diffracting objects. If the obstructing object provides multiple, closely-spaced openings, a complex pattern of varying intensity can result. This is due to the superposition, or interference, of different parts of a wave that traveled to the observer by different paths (see diffraction grating).
The formalism of diffraction can also describe the way in which waves of finite extent propagate in free space. For example, the expanding profile of a laser beam, the beam shape of a radar antenna and the field of view of an ultrasonic transducer are all explained by diffraction theory.
PROTON
ReplyDelete..The proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom, along with neutrons, but is also stable by itself and has a second identity as the hydrogen ion, H+. It is composed of three fundamental particles: two up quarks and one down quark.[3]
Contents
[hide]
* 1 Description
* 2 Stability
* 3 Quarks and the mass of the proton
* 4 The proton in chemistry
o 4.1 Atomic number
o 4.2 Hydrogen as proton
* 5 History
* 6 Exposure
* 7 Antiproton
* 8 See also
* 9 References
* 10 External links
[edit] Description
Protons are spin-½ fermions and are composed of three quarks,[4] making them baryons. The two up quarks and one down quark of the proton are held together by the strong force, mediated by gluons.[3] The proton has an approximately exponentially decaying positive charge distribution with a mean square radius of about 0.8 fm.[5]
Protons and neutrons are both nucleons, which may be bound by the nuclear force into atomic nuclei. The nucleus of the most common isotope of the hydrogen atom is a single proton (it contains no neutrons). The nuclei of heavy hydrogen (deuterium and tritium) contain neutrons. All other types of atoms are composed of two or more protons and various numbers of neutrons. The number of protons in the nucleus determines the chemical properties of the atom and thus which chemical element is represented; it is the number of both neutrons and protons in a nuclide which determine the particular isotope of an element.
[edit] Stability
Main article: Proton decay
Protons are observed to be stable and their empirically observed half-life is at least 6.6×1035 years.[6] Grand unified theories generally predict that proton decay should take place, although experiments so far have only resulted in a lower limit of 1035 years for the proton's lifetime. In other words, proton decay has never been witnessed and the experimental lower bound on the mean proton lifetime (2.1×1029 years) is given by the Sudbury Neutrino Observatory.[7]
VOLUME
ReplyDeleteThe volume of any solid, liquid, gas, plasma, or vacuum is how much three-dimensional space it occupies, often quantified numerically. One-dimensional figures (such as lines) and two-dimensional shapes (such as squares) are assigned zero volume in the three-dimensional space. Volume is commonly presented in units such as cubic meters, cubic centimeters, liters, or milliliters.
Volumes of some simple shapes, such as regular, straight-edged, and circular shapes can be easily calculated using arithmetic formulas. More complicated shapes can be calculated by integral calculus if a formula exists for its boundary. The volume of any shape can be determined by displacement.
In differential geometry, volume is expressed by means of the volume form, and is an important global Riemannian invariant.
Volume is a fundamental parameter in thermodynamics and it is conjugate to pressure.
:-)
MAGNETIC
ReplyDeleteMagnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field.
For the physics of magnetic materials, see magnetism and magnet, more specifically ferromagnetism, paramagnetism, and diamagnetism. For constant magnetic fields, such as are generated by magnetic materials and steady currents, see magnetostatics. A changing magnetic field generates an electric field and a changing electric field results in a magnetic field. (See electromagnetism.)
In view of special relativity, the electric and magnetic fields are two interrelated aspects of a single object, called the electromagnetic field. A pure electric field in one reference frame is observed as a combination of both an electric field and a magnetic field in a moving reference frame.
In modern physics, the magnetic (and electric) fields are understood to be due to a photon field; in the language of the Standard Model the electromagnetic force is mediated by photons. Most often this microscopic description is not needed because the simpler classical theory covered in this article is sufficient; the difference is negligible under most circumstances.
Electromagnetic radiation
ReplyDelete(often abbreviated E-M radiation or EMR) is a phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It consists of electric and magnetic field components which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. Electromagnetic radiation is classified into several types according to the frequency of its wave; these types include (in order of increasing frequency and decreasing wavelength): radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. A small and somewhat variable window of frequencies is sensed by the eyes of various organisms; this is what is called the visible spectrum, or light.
EM radiation carries energy and momentum that may be imparted to matter with which it interacts.
theory:
Electromagnetic waves were first postulated by James Clerk Maxwell and subsequently confirmed by Heinrich Hertz. Maxwell derived a wave form of the electric and magnetic equations, revealing the wave-like nature of electric and magnetic fields, and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave.
According to Maxwell's equations, a spatially-varying electric field generates a time-varying magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form an electromagnetic wave.
A quantum theory of the interaction between electromagnetic radiation and matter such as electrons is described by the theory of quantum electrodynamics.
Sources of energy
ReplyDeleteEnergy is the vital force powering business, manufacturing, and the transportation of goods and services to serve the American and world economies. Energy supply and demand plays an increasingly vital role in our national security and the economic output of our nation. It is not surprising that the United States spends over 500 billion dollars annually on energy.
purple electricity emanating from a center ball
Increasing energy supplies.
As America's need for energy grows, the Department of Energy is meeting the challenge by establishing clean fuel initiatives to make the most of traditional fossil fuels while investing in cutting edge research to develop sustainable sources such as fusion and to employ hydrogen (an energy carrier like electricity) which can be produced from diverse, domestic sources and greatly reduce our dependence on imported oil.
part of industrial building
Modernizing our energy infrastructure.
By developing the infrastructure to support these fuels, DOE is striving every day to protect our nation's energy needs and our planet's environment.
ripples in a pool of water
Ensuring the productive and optimal use of energy resources, while limiting environmental impact.
In addition, the Department of Energy is harnessing the power of the earth itself to meet our energy needs. Advances in wind, hydro and geothermal energy allow us to take advantage of clean, abundant energy.
honeycomb against a black background
Cooperating on international energy issues.
The Department’s activities are instrumental in establishing the safety, reliability, and efficiency of energy supplies in a global marketplace.
Buoyant Force
ReplyDeleteA completely submerged body displaces a volume of liquid equal to itsown volume. Experience also tell us that when an object is submerged, itappear lighter in weight; the water buoys it up, pushed upward, partiallysupporting it somehow. Archimedes' Buoyancy Principle asserts that
an object immersed in a liquid will be lighter by an amountequal to the weight of the fluid it displaces.
The upward force exerted by the fluid is known as buoyant force.
Buoyant force is caused by gravity acting on the fluid. It has its originin the pressure difference occurring between the top and bottom of theimmersed object, a difference that always exists when pressure varies withdepth. Imaging without the object, the same immersed space will be occupiedby the same volume of fluid.
The weight of those fluid is supported by other parts of the fluid.So the buoyant force is the weight of the displaced fluid. I hope thisjava applet will help you learn more about buoyancy.
said...
ReplyDeleteforce...
In physics, the concept of force is used to describe an influence which causes a free massive body to undergo an acceleration. Forces which do not act uniformly on all parts of a body will also cause mechanical stresses.[1]
Force can also be described by intuitive concepts such as a push or pull that can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate, or which can cause a flexible object to deform. Related concepts to accelerating forces include thrust - any force which increases the velocity of the object, drag - any force which decreases the velocity of any object, and torque - the tendency of a force to cause changes in rotational speed about an axis. Alternatively, mechanical stress is a technical term for the efforts which cause deformation of matter, be it solid, liquid, or gaseous. While mechanical stress can remain embedded in a solid object, gradually deforming it, mechanical stress in a fluid determines changes in its pressure and volume.[2][3]
An applied force has both magnitude and direction, making it a vector quantity. Newton's second law states that an object with a constant mass will accelerate in proportion to the net force acting upon and in inverse proportion to its mass. Equivalently, the net force, on an object equals the rate at which its momentum changes.[4]
Philosophers in antiquity have used the concept of force in the study of stationary and moving objects. Aristotle attempted to define this concept in detail but incorporated fundamental misunderstandings that lasted many centuries. Archimedes developed a better understanding of force by observing simple machines, but many in his time still believed Aristotle's concept of force.[5] When the Age of Enlightenment began, Sir Isaac Newton corrected these misunderstandings with mathematical insight that remained unchanged for nearly three hundred years.[3] By the early 20th century, Einstein developed the theory of Special Relativity to correctly predict how forces increase exponentially for particles approaching the speed of light.
With modern insights into quantum mechanics and technology that can accelerate particles close to the speed of light, particle physics has devised a Standard Model to describe forces between particles smaller than atoms. The Standard Model predicts that exchange particles called gauge bosons are the fundamental means by which forces are emitted and absorbed. Only four main interactions are known: in order of decreasing strength, they are: strong, electromagnetic, weak, and gravitational.[2] High-energy particle physics observations made during the 1970s and 1980s confirmed that the weak and electromagnetic forces are expressions of a more fundamental electroweak interaction.[6]
Conservation of energy
ReplyDeleteThe law of conservation of energy is an empirical law of physics. It states that the total amount of energy in an isolated system remains constant over time (is said to be conserved over time). A consequence of this law is that energy can neither be created nor destroyed, it can only be transformed from one state to another. The only thing that can happen to energy in a closed system is that it can change form, for instance chemical energy can become kinetic energy.
Albert Einstein's theory of relativity shows that energy and mass are the same thing, and that neither one appears without the other. Thus in closed systems, both mass and energy are conserved separately, just as was understood in pre-relativistic physics. The new feature of relativistic physics is that "matter" particles (such as those constituting atoms) could be converted to non-matter forms of energy, such as light; or kinetic and potential energy (example: heat). However, this conversion does not affect the total mass of systems, since the latter forms of non-matter energy still retain their mass through any such conversion.
Today, conservation of “energy” refers to the conservation of the total system energy over time. This energy includes the energy associated with the rest mass of particles and all other forms of energy in the system. In addition the invariant mass of systems of particles (the mass of the system as seen in its center of mass inertial frame, such as the frame in which it would need to be weighed), is also conserved over time for any single observer, and (unlike the total energy) is the same value for all observers. Therefore, in an isolated system, although matter (particles with rest mass) and "pure energy" (heat and light) can be converted to one another, both the total amount of energy and the total amount of mass of such systems remain constant over time, as seen by any single observer. If energy in any form is allowed to escape such systems (see binding energy) the mass of the system will decrease in correspondence with the loss.
Principle of physics according to which the energy of interacting bodies or particles in a closed system remains constant, though it may take different forms (e.g., kinetic energy, potential energy, thermal energy, energy in an electric current, or energy stored in an electric field, in a magnetic field, or in chemical bonds [see bonding]). With the advent of relativity physics in 1905, mass was recognized as equivalent to energy. When accounting for a system of high-speed particles whose mass increases as a consequence of their speed, the laws of conservation of energy and conservation of mass become one conservation law.
The principle of conservation of energy states that energy cannot be created or destroyed, although it can be changed from one form to another. Thus in any isolated or closed system, the sum of all forms of energy remains constant. The energy of the system may be interconverted among many different forms—mechanical, electrical, magnetic, thermal, chemical, nuclear, and so on—and as time progresses, it tends to become less and less available; but within the limits of small experimental uncertainty, no change in total amount of energy has been observed in any situation in which it has been possible to ensure that energy has not entered or left the system in the form of work or heat. For a system that is both gaining and losing energy in the form of work and heat, as is true of any machine in operation, the energy principle asserts that the net gain of energy is equal to the total change of the system's internal energy.
Voltage
ReplyDeleteVoltage is electric potential energy per unit charge, measured in joules per coulomb ( = volts). It is often referred to as "electric potential", which then must be distinguished from electric potential energy by noting that the "potential" is a "per-unit-charge" quantity. Like mechanical potential energy, the zero of potential can be chosen at any point, so the difference in voltage is the quantity which is physically meaningful. The difference in voltage measured when moving from point A to point B is equal to the work which would have to be done, per unit charge, against the electric field to move the charge from A to B.
The voltage between two (electron) positions "A" and "B", inside a solid electrical conductor (or inside two electrically-connected, solid electrical conductors), is denoted by (VA − VB). This voltage is the electrical driving force that drives a conventional electric current in the direction A to B. Voltage can be directly measured by a voltmeter. Well-constructed, correctly used, real voltmeters approximate very well to ideal voltmeters. An analogy involving the flow of water is sometimes helpful in understanding the concept of voltage.
Voltage, also called electromotive force, is a quantitative expression of the potential difference in charge between two points in an electrical field. The greater the voltage, the greater the flow of electrical current (that is, the quantity of charge carriers that pass a fixed point per unit of time) through a conducting or semiconducting medium for a given resistance to the flow. Voltage is symbolized by an uppercase italic letter V or E. The standard unit is the volt, symbolized by a non-italic uppercase letter V. One volt will drive one coulomb (6.24 x 1018) charge carriers, such as electrons, through a resistance of one ohm in one second.
Voltage can be direct or alternating. A direct voltage maintains the same polarity at all times. In an alternating voltage, the polarity reverses direction periodically. The number of complete cycles per second is the frequency, which is measured in hertz (one cycle per second), kilohertz, megahertz, gigahertz, or terahertz. An example of direct voltage is the potential difference between the terminals of an electrochemical cell. Alternating voltage exists between the terminals of a common utility outlet.
A voltage produces an electrostatic field, even if no charge carriers move (that is, no current flows). As the voltage increases between two points separated by a specific distance, the electrostatic field becomes more intense. As the separation increases between two points having a given voltage with respect to each other, the electrostatic flux density diminishes in the region between them.
Manhattan Project!!!
ReplyDeleteJust before the First World War, two German scientists, James Franck and Gustav Hertz, carried out experiments where they bombarded mercury atoms with electrons and traced the energy changes that resulted from the collisions. Their experiments helped to substantiate they theory put forward by Nils Bohr that an atom can absorb internal energy only in precise and definite amounts.
In 1921 two Otto Hahn and Lise Meitner, discovered nuclear isomers. Over the next few years they devoted their time to researching the application of radioactive methods to chemical problems. In the 1930s they became interested in the research being carried out by Enrico Fermi and Emilio Segre at the University of Rome. This included experiments where elements such as uranium were bombarded with neutrons. By 1935 the two men had discovered slow neutrons, which have properties important to the operation of nuclear reactors.
Otto Hahn and Lise Meitner were now joined by Fritz Strassmann and discovered that uranium nuclei split when bombarded with neutrons. In 1938 Meitner, like other Jews in Nazi Germany, was dismissed from her university post. She moved to Sweden and later that year she wrote a paper on nuclear fission with her nephew, Otto Frisch, where they argued that by splitting the atom it was possible to use a few pounds of uranium to create the explosive and destructive power of many thousands of pounds of dynamite.
In January, 1939 a Physics Conference took place in Washington in the United States. A great deal of discussion concerned the possibility of producing an atomic bomb. Some scientists argued that the technical problems involved in producing such a bomb were too difficult to overcome, but the one thing they were agreed upon was that if such a weapon was developed, it would give the country that possessed it the power to blackmail the rest of the world. Several scientists at the conference took the view that it was vitally important that all information on atomic power should be readily available to all nations to stop this happening.
ReplyDeleteOn 2nd August, 1939, three Jewish scientists who had fled to the United States from Europe, Albert Einstein, Leo Szilard and Eugene Wigner, wrote a joint letter to President Franklin D. Roosevelt, about the developments that had been taking place in nuclear physics. They warned Roosevelt that scientists in Nazi Germany were working on the possibility of using uranium to produce nuclear weapons. Roosevelt responded by setting up a scientific advisory committee to investigate the matter. He also had talks with the British government about ways of sabotaging the German efforts to produce nuclear weapons.
In May, 1940, the German Army invaded Denmark, the home of Niels Bohr, the world's leading expert on atomic research. It was feared that he would be forced to work for Nazi Germany. With the help of the British Secret Service he escaped to Sweden before being moving to the United States.
In 1942 the Manhattan Engineer Project was set up in the United States under the command of Brigadier General Leslie Groves. Scientists recruited to produce an atom bomb included Robert Oppenheimer (USA), David Bohm (USA), Leo Szilard (Hungary), Eugene Wigner (Hungary), Rudolf Peierls (Germany), Otto Frisch (Germany), Niels Bohr (Denmark), Felix Bloch (Switzerland), James Franck (Germany), James Chadwick (Britain), Emilio Segre (Italy), Enrico Fermi (Italy), Klaus Fuchs (Germany) and Edward Teller (Hungary).
Winston Churchill and Franklin D. Roosevelt were deeply concerned about the possibility that Germany would produce the atom bomb before the allies. At a conference held in Quebec in August, 1943, it was decided to try and disrupt the German nuclear programme.
In February 1943, SOE saboteurs successfully planted a bomb in the Rjukan nitrates factory in Norway. As soon as it was rebuilt it was destroyed by 150 US bombers in November, 1943. Two months later the Norwegian resistance managed to sink a German boat carrying vital supplies for its nuclear programme.
Lenz's Law
ReplyDelete>A law of electromagnetism which states that,whenever there is an induced electromotive force(emf)in a conductor,it is alaways in such a direction that the current it would produce would oppose the change which causes the induced emf.If the change is the motion of a conductor through a magnetic field, the induced current must be in such a direction as to produce aforce opposing the motion .If the change causing the emf is a change of flux threading a coil, the induced current must produce a flux in such a direction as to oppose the change.Lenz's law is a form of the law of conversation of energy ,since it states that a change cannot propagate itself.
distance vs. displacement
ReplyDeleteDistance and displacement are different quantities, but they are related. If you take the first example of the walk around the desk, it should be apparent that sometimes the distance is the same as the magnitude of the displacement. This is the case for any of the one meter segments but is not always the case for groups of segments. As I trace my steps completely around the desk the distance and displacement of my journey soon begin to diverge. The distance traveled increases uniformly, but the displacement fluctuates a bit and then returns to zero.
Distance is a scalar measure of the interval between two locations measured along the actual path connecting them. Displacement is a vector measure of the interval between two locations measured along the shortest path connecting them.
In the case of one and the same uniform motion, the distance traversed during a longer interval of time is greater than the distance traversed during a shorter interval of time.
Formula:
D= (S)(T), Distance =Speed x Time
example:
Mr. Smiths bike travels at an average of 8km/hr. If he rides to Coach Anderson's house 24 km away, how long does it take to get there?
T=D/S
24 km/8kmhr=
-=the End=-
3hrs
DENSITY
ReplyDeleteThe density of a material is defined as its mass per unit volume. The symbol of density is ρ (the Greek letter rho).
Formula
Mathematically:
\rho = \frac{m}{V} \,
where:
ρ (rho) is the density,
m is the mass,
V is the volume.
Different materials usually have different densities, so density is an important concept regarding buoyancy, metal purity and packaging.
In some cases density is expressed as the dimensionless quantities specific gravity (SG) or relative density (RD), in which case it is expressed in multiples of the density of some other standard material, usually water or air/gas.
History
In a well-known tale, Archimedes was given the task of determining whether King Hiero's goldsmith was embezzling gold during the manufacture of a wreath dedicated to the gods and replacing it with another, cheaper alloy.[1]
Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass; but the king did not approve of this.
Baffled, Archimedes took a relaxing immersion bath and observed from the rise of the warm water upon entering that he could calculate the volume of the gold crown through the displacement of the water. Allegedly, upon this discovery, he went running naked through the streets shouting, "Eureka! Eureka!" (Εύρηκα! Greek "I found it"). As a result, the term "eureka" entered common parlance and is used today to indicate a moment of enlightenment.
The story first appeared in written form in Vitruvius' books of architecture, two centuries after it supposedly took place.[2] Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time.
Measurement of density
For a homogeneous object, the mass divided by the volume gives the density. The mass is normally measured with an appropriate scale or balance; the volume may be measured directly (from the geometry of the object) or by the displacement of a fluid. Hydrostatic weighing is a method that combines these two.
If the body is not homogeneous, then the density is a function of the position: \rho(\vec{r})=dm/dv, where dv is an elementary volume at position \vec{r}. The mass of the body then can be expressed as
m = \int_V \rho(\vec{r}) dV
The density of a solid material can be ambiguous, depending on exactly how its volume is defined, and this may cause confusion in measurement. A common example is sand: if it is gently poured into a container, the density will be low; if the same sand is compacted into the same container, it will occupy less volume and consequently exhibit a greater density. This is because sand, like all powders and granular solids, contains a lot of air space in between individual grains. The density of the material including the air spaces is the bulk density, which differs significantly from the density of an individual grain of sand with no air included.
This comment has been removed by the author.
ReplyDeleteHUYGENS'S PRINCIPLE
ReplyDeleteThe Huygens–Fresnel principle [1] (named for Dutch physicist Christiaan Huygens, and French physicist Augustin-Jean Fresnel) is a method of analysis applied to problems of wave propagation (both in the far field limit and in near field diffraction). It recognizes that each point of an advancing wave front is in fact the center of a fresh disturbance and the source of a new train of waves; and that the advancing wave as a whole may be regarded as the sum of all the secondary waves arising from points in the medium already traversed. This view of wave propagation helps better understand a variety of wave phenomena, such as diffraction.
For example, if two rooms are connected by an open doorway and a sound is produced in a remote corner of one of them, a person in the other room will hear the sound as if it originated at the doorway. As far as the second room is concerned, the vibrating air in the doorway is the source of the sound. The same is true of the light passing the edge of an obstacle, but this is not as easily observed because of the short wavelength of visible light.
A common application of Huygens' principle is for the case of a plane wave (usually light, radio waves, x-rays or electrons) incident on an aperture of arbitrary shape. Huygens' principle states that each point in the hole acts as a point source. A point source generates waves that travel spherically in all directions (similar to circular waves caused by dropping small stone in a pond). The sum of the waves from all the point sources at any point beyond the aperture can be calculated by integration or numerical modelling.
Infrasound
ReplyDeleteFrom Wikipedia, the free encyclopedia
Infrasound is sound that is lower in frequency than 20 Hz (Hertz) or cycles per second, the normal limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. The ear is the primary organ for sensing infrasound, but at higher levels it is possible to feel infrasound vibrations in various parts of the body.
The study of such sound waves is sometimes referred to as infrasonics, covering sounds beneath 20 Hz down to 0.001 Hz. This frequency range is utilized for monitoring earthquakes, charting rock and petroleum formations below the earth, and also in ballistocardiography and seismocardiography to study the mechanics of the heart. Infrasound is characterized by an ability to cover long distances and get around obstacles with little dissipation.
Possibly the first observation of naturally occurring infrasound was in the aftermath of the 1883 eruption of Krakatoa, when concussive acoustic waves circled the globe seven times or more and were recorded on barometers worldwide.[citation needed] Infrasound was also used by Allied forces in World War I to locate artillery. One of the pioneers in infrasonic research was French scientist Vladimir Gavreau, born in Russia as Vladimir Gavronsky.[1] His interest in infrasonic waves first came about in his lab during the 1960s, when he and his lab assistants experienced pain in the ear drums and shaking lab equipment, but no audible sound was picked up on his microphones. He concluded it was infrasound and soon got to work preparing tests in the labs. One of his experiments was an infrasonic whistle.
A number of American universities have active research programs in infrasound, including the University of Mississippi, Southern Methodist University, the University of California at San Diego, the University of Alaska Fairbanks, and the University of Hawaii at Manoa.
Infrasound sometimes results naturally from severe weather, surf,[5] lee waves, avalanches, earthquakes, volcanoes, bolides,[6] waterfalls, calving of icebergs, aurora, lightning and upper-atmospheric lightning.[7] Nonlinear ocean wave interactions in ocean storms produce pervasive infrasound vibrations around 0.2 Hz, known as microbaroms.[8] Infrasound can also be generated by man-made processes such as sonic booms and explosions (both chemical and nuclear), by machinery such as diesel engines and older designs of down tower wind turbines and by specially designed mechanical transducers (industrial vibration tables) and large-scale subwoofer loudspeakers.[9] The Comprehensive Nuclear-Test-Ban Treaty Organization uses infrasound as one of its monitoring technologies (along with seismic, hydroacoustic, and atmospheric radionuclide monitoring).
Whales, elephants, hippopotamuses, rhinoceros, giraffes, okapi, and alligators are known to use infrasound to communicate over distances—up to hundreds of miles in the case of whales. It has also been suggested that migrating birds use naturally generated infrasound, from sources such as turbulent airflow over mountain ranges, as a navigational aid.[10] Elephants, in particular, produce infrasound waves that travel through solid ground and are sensed by other herds using their feet, although they may be separated by hundreds of kilometres.
Scientists accidentally discovered that the spinning core or vortex of a tornado creates infrasonic waves. When the vortices are large, the frequencies are lower; smaller vortices have higher, though still infrasonic, frequencies. These low frequency sound waves can be detected for up to 160 kilometres (100 mi) away and can help provide early warning of tornadoes
cLaRiSsA aSk ???
ReplyDeletewHat is aCcELeRator ???
aNswer ;
Accelerator physics deals with the problems of building and operating particle accelerators.
The experiments conducted with particle accelerators are not regarded as part of accelerator physics. These belong (according to the objectives of the experiments) to particle physics, nuclear physics, condensed matter physics, materials physics, etc. as well as to other sciences and technical fields. The types of experiments done at a particular accelerator and/or its other uses are largely constrained by the characteristics of the accelerator itself, such as energy (per particle), types of particles, beam intensity, beam quality, etc.
Accelerator physics itself is the study of the motion of the particle beam through the machine, control and manipulation of the beam, interaction with the machine itself, and measurements of the various parameters associated with particle beams.
Contents [hide]
1 Equations of motion
2 Diagnostics
3 Machine tolerances
4 Interactions between the beam and the machine
5 See also
6 External links
[edit] Equations of motion
The motion of charged particles through an accelerator is controlled using applied electro-magnetic fields, and the equations of motion may be derived from (or, since in many cases a general solution is not possible, approximated from) relativistic Hamiltonian mechanics. Typically, a separate Hamiltonian is written down for each element (e.g. for a single quadrupole magnet, or accelerating structure) to allow the equations of motion to be solved for this one element. Once this has been done for each element encountered in the machine, the full trajectory of each particle may be calculated for the entire machine.
In many cases a general solution of the full Hamiltonian is not possible, so it is necessary to make approximations. This may take the form of the Paraxial approximation (a Taylor series in the dynamical variables, truncated to low order), however, even in the cases of strongly non-linear magnetic fields, a Lie transform may be used to construct an integrator with a high degree of accuracy, and the paraxial approximation is not necessary.
[edit] Diagnostics
A vital component of any accelerator are the diagnostic devices that allow various properties of the particle bunches to be measured.
A typical machine may use many different types of measurement device in order to measure different properties. These include (but are not limited to) Beam Position Monitors (BPMs) to measure the position of the bunch, screens (fluorescent screens, Optical Transition Radiation (OTR) devices) to image the profile of the bunch, wire-scanners to measure its cross-section, and toroids or ICTs to measure the bunch charge (i.e. the number of particles per bunch).
While many of these devices rely on well understood technology, designing a device capable of measuring a beam for a particular machine is a complex task requiring much expertise. Not only is a full understanding of the physics of the operation of the device necessary, but it is also necessary to ensure that the device is capable of measuring the expected parameters of the machine under consideration.
Success of the full range of beam diagnostics often underpins the success of the machine as a whole.
eNd !!! cLariSSa_32 (^,(")
Electromagnetic radiation
ReplyDelete(often abbreviated E-M radiation or EMR) is a phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It consists of electric and magnetic field components which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. Electromagnetic radiation is classified into several types according to the frequency of its wave; these types include (in order of increasing frequency and decreasing wavelength): radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. A small and somewhat variable window of frequencies is sensed by the eyes of various organisms; this is what is called the visible spectrum, or light.
EM radiation carries energy and momentum that may be imparted to matter with which it interacts.
theory:
Electromagnetic waves were first postulated by James Clerk Maxwell and subsequently confirmed by Heinrich Hertz. Maxwell derived a wave form of the electric and magnetic equations, revealing the wave-like nature of electric and magnetic fields, and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave.
According to Maxwell's equations, a spatially-varying electric field generates a time-varying magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form an electromagnetic wave.
A quantum theory of the interaction between electromagnetic radiation and matter such as electrons is described by the theory of quantum electrodynamics.
Electromagnetism
ReplyDeleteAn electromagnet is an object that acts like a magnet, but its magnetic force is created and controlled by electricity—thus the name electromagnet.
By wrapping insulated wire around a piece of iron and then running electrical current through the wire, the iron becomes magnetized. This happens because a magnetic field is created around a wire when it has electrical current running through it. Creating a coil of wire concentrates the field. Wrapping the wire around an iron core greatly increases the strength of the magnetic field.
Making an electromagnet
If you wrap a wire around an iron core, such as a nail, and you send electrical current through the wire, the nail will become highly magnetized. You can verify that by picking up small objects or by showing its effect on a compass. This is called an electromagnet.
Insulated wire
Note that the wire must be an insulated wire. A bare wire would cause an electrical short and the current would then run through the nail or metal core. In some electromagnets, like in an electric motor, the wire will look like bare copper, but it is insulated with a thin coating of a clear material.
Also, if the wire is thin, it may get warm from the resistance to the electricity passing through it.
Turn on and off
The most interesting feature of the electromagnet is that when the electrical current is turned off, the magnetism is also turned off. This is especially true if the core is made of soft iron, which quickly loses its magnetism. Hardened steel may retain its magnetism, so you can't use the most valuable feature of an electromagnet.
Being able to turn the magnetism on and off has lead to many amazing inventions and applications.
How electromagnetism works
When electricity passed through a wire, a magnetic field is created around the wire. Looping the wire increases the magnetic field. Adding an iron core greatly increases the effect and creates an electromagnet. You can create an electromagnet without the iron core. That is usually called a solenoid.
Magnetic field
When DC electricity is passed through a wire, a magnetic field rotates around the wire in a specific direction.
Compass can show field
Connecting a wire to a battery and placing a compass near the wire can demonstrate a magnetic field. When the current is turned on, the compass-needle will move. If you reverse the direction of the current, the needle will move in the opposite direction.
Right hand rule
To find the direction the magnetic field is going, you can use the "right-hand rule" to determine it. If you take your right hand and wrap it around the wire, with your thumb pointing in the direction of the electrical current (positive to negative), then your fingers are pointing in the direction of the magnetic field around the wire. Try it with the picture above.
Wire in a coil
Wrapping the wire in a coil concentrates and increases the magnetic field, because the additive effect of each turn of the wire.
A coil of wire used to create a magnetic field is called a solenoid.
Iron core
Wrapping the wire around an iron core greatly increases the magnetic field. If you put a nail in the coil in the drawing above, it would result in an electromagnet with the a north seeking pole on the "N" side.
Using AC electricity
If AC electricity is used, the electromagnet has the same properties of a magnet, except that the polarity reverses with the AC cycle.
Note that it is not a good idea to try to make an AC electromagnet. This is because of the high voltage in house current. Using a wire around a nail would result in a blown fuse in the AC circuit box. There is also the potential of an electric shock.
ezter :p
VOLTAGE
ReplyDeleteThe voltage between two (electron) positions "A" and "B", inside a solid electrical conductor (or inside two electrically-connected, solid electrical conductors), is denoted by (VA − VB). This voltage is the electrical driving force that drives a conventional electric current in the direction A to B. Voltage can be directly measured by a voltmeter. Well-constructed, correctly used, real voltmeters approximate very well to ideal voltmeters. An analogy involving the flow of water is sometimes helpful in understanding the concept of voltage (see below).
Precise modern and historic definitions of voltage exist, but (due to the development of the electron theory of metal conduction in the period 1897 to 1933, and to developments in theoretical surface science from about 1910 to about 1950, particularly the theory of local work function) some older definitions are no longer regarded as strictly correct. This is because they neglect the existence of "chemical" effects and surface effects. A particular lesson from surface science is that, to get consistency and universality, formal definitions must relate to positions or (better) electron states inside conductors.
In conduction processes occurring in metals and most other solids, electric currents consist almost exclusively of the flow of electrons in the direction B to A. This movement of electrons is controlled by differences in a so-called "total local thermodynamic potential" often denoted by the symbol µ ("mu"). This parameter is often called the "local Fermi level" or sometimes the "(local) electrochemical potential of an electron" or the "total (local) chemical potential of an electron". The modern electron-based definition of voltage (VA − VB) is in terms of differences in µ:
Currents don't have Voltage............;;;
ReplyDeleteVoltage is not a characteristic of electric current. It's a common mistake to believe that a current "has a voltage" (and this mistake is probably associated with the 'current electricity' misconception, where people believe that 'current' is a kind of substance that flows). Voltage and current are two independent things. It is easy to create a current which lacks a voltage: just short out an electromagnet coil. It is also easy to create a voltage without a current: flashlight batteries maintain their voltage even when they are sitting on the shelf in the store. Water analogy: Think of water pressure without a flow. That's like voltage alone. Now think of water that's coasting along; a water flow without a pressure. That's like electric current alone.
TOPIC: Friction
ReplyDeletefriction forces causes energy loss that has enormous practical importance. it is estimated that in the U.S. Alone, the cost of our imperfect understanding in friction is more than 500 billion dollars.friction which is worse in vacuum, has caused irreversible failures in many space instruments. on the other hand, friction is useful in many instances. without friction we would not able to walk, cars will not moved,and violins would not work.in other cases one wants to maximize friction, like when stopping a train.
the frictional force is also presumed to be proportional to the coefficient of friction. however, the amount of force required to move an object starting from rest it usually its greater than the force required to keep it moving in constant once it is started. therefore the two coefficient are sometimes quoted for a given pair of surface- the coefficient of static friction and a coefficient of kinetic friction. the force expression above can be called the standard model of surface friction and is dependent upon several assumptions about friction.
Title:
ReplyDeleteMOMENTUM
Momentum of the system does not change value. This allows one to calculate and predict the outinteracting momentum is the product of mass and velocityof an object.It has a formula of p=mv.It is a corner stone concept in physics.With a closed system of objects,the total comes when objects bounce into one another. Or, by knowing the outcome of a collision, one can reason what was the initial state of the system.
When an object is moving, it has a non-zero momentum. If an object is standing still, then its momentum is zero. To calculate the momentum of a moving object multiply the mass of the object times its velocity. The symbol for momentum is a small p.
* EXAMPLE OF MOMENTUM CALCULATION:
Find the momentum of an oject that has a mass of 2.0 kg and has a velocity of 4.0 m/s.
m=2.0 kg
v=4.0 m/s
p=?
p=mv
p=(2.0kg)(4.0m/s)
p=8.0 kg m/s
Momentum is also a vector.That means, that momentum is a quantity that has a magnitude, or size, and a direction. The above problem is a one dimensional problem. That is, the object is moving along a straight line. In situations like this the momentum is usually stated to be positive, to the right, or negative,to the left. So, in the above problem one would say that the momentum is 'positive 8.0 kg-m/s', or '8.0 kg-m/s to the right.' Usually, though, in simple cases like this we just say that the momentum is '8.0 kg-m/s' with the positive sign understood.
Momentum problems can become more complicated, however. Soon, you will be doing momentum problems in two and three dimensions. Under these conditions, say in a two dimensional problem, one would state a momentum using language such as '3.0 kg-m/s in a direction of 50 degrees North of West.'
At first, though, our momentum problems will be in only one dimension. We will imagine objects traveling in a straight line.
Sometimes the concept of momentum is confused with the concept of velocity. Do not do this. Momentum is related to velocity. In fact, they both have the same direction. That is, if an object has a velocity that is aimed toward the right, then its momentum will also be directed to the right. However, momentum is made up of both mass and velocity. One must take the mass and multiply it by the velocity to get the momentum.
FRICTION........................
ReplyDeleteFriction is the force resisting the relative lateral ,motion of solid surfaces, or material elements in contact. It is usually subdivided into several varieties:
* Dry friction resists relative lateral motion of two solid surfaces in contact. Dry friction is also subdivided into static friction between non-moving surfaces, and kinetic friction (sometimes called sliding friction or dynamic friction) between moving surfaces.
* Lubricated friction or fluid friction resists relative lateral motion of two solid surfaces separated by a layer of gas or liquid.
ReplyDelete* Fluid friction is also used to describe the friction between layers within a fluid that are moving relative to each other.
* Skin friction is a component of drag, the force resisting the motion of a solid body through a fluid.
* Internal friction is the force resisting motion between the elements making up a solid material while it undergoes deformation.
DYNAMICS
ReplyDeleteDynamics (from Greek δυναμικός - dynamikos "powerful", from δύναμις - dynamis "power") may refer to:
* Dynamics (music), In music, dynamics refers to the softness or loudness of a sound or note. The term is also applied to the written or printed musical notation used to indicate dynamics (also known as volume in a song)
FIELDS
* Analytical dynamics refers to the motion of bodies as induced by external forces
* Flight dynamics, the science of aircraft and spacecraft design
* Force Dynamics
* Fluid dynamics, the study of fluid flow
o Computational fluid dynamics
* Molecular dynamics, the study of motion on the molecular level
o Langevin dynamics
+ Brownian dynamics
* In quantum physics, dynamics may refer to how forces are quantized, as in quantum electrodynamics or quantum chromodynamics
* Relativistic dynamics may refer to a combination of relativistic and quantum concepts
* Stellar dynamics
* System dynamics, the study of the behaviour of complex systems
* Thermodynamics, a branch of physics that studies the relationships between heat and mechanical energy
[edit] Branch
* Aerodynamics, the study of gases in motion
* Hydrodynamics, the study of liquids in motion
* Neurodynamics, an area of research in the brain sciences which places a strong focus upon the spatio-temporal (dynamic) character of neural activity in describing brain function
* Thermodynamics
ALPHA DECAY.......................
ReplyDeleteAn alpha particle is the same as a helium-4 nucleus, and both mass number and atomic number are the same.
Alpha decay is by far the most common form of cluster decay where the parent atom ejects a defined daughter collection of nucleons, leaving another defined product behind (in nuclear fission, a number of different pairs of daughters of approximately equal size are formed). Alpha decay is the most likely cluster decay because of the combined extremely high binding energy and relatively small mass of the helium-4 product nucleus
Alpha decay, like other cluster decays, is fundamentally a quantum tunneling process. Unlike beta decay, alpha decay is governed by the interplay between the nuclear force and the electromagnetic force.
Alpha decay is a mode of radioactive decay seen only in heavier nuclides, with the lightest known alpha emitter being the lightest isotopes (mass numbers 106–110) of tellurium (element 52).
ARCHIMEDES THEORY
ReplyDeleteArchimedes' principle does not consider the surface tension (capillarity) acting on the body.[3]
The weight of the displaced fluid is directly proportional to the volume of the displaced fluid (if the surrounding fluid is of uniform density). Thus, among completely submerged objects with equal masses, objects with greater volume have greater buoyancy.
Suppose a rock's weight is measured as 10 newtons when suspended by a string in a vacuum. Suppose that when the rock is lowered by the string into water, it displaces water of weight 3 newtons. The force it then exerts on the string from which it hangs would be 10 newtons minus the 3 newtons of buoyant force: 10 − 3 = 7 newtons. Buoyancy reduces the apparent weight of objects that have sunk completely to the sea floor. It is generally easier to lift an object up through the water than it is to pull it out of the water.
Assuming Archimedes' principle to be reformulated as follows,
ARCHIMEDES PRINCIPLE
ReplyDeleteArchimedes' principle does not consider the surface tension (capillarity) acting on the body.[3]
The weight of the displaced fluid is directly proportional to the volume of the displaced fluid (if the surrounding fluid is of uniform density). Thus, among completely submerged objects with equal masses, objects with greater volume have greater buoyancy.
Suppose a rock's weight is measured as 10 newtons when suspended by a string in a vacuum. Suppose that when the rock is lowered by the string into water, it displaces water of weight 3 newtons. The force it then exerts on the string from which it hangs would be 10 newtons minus the 3 newtons of buoyant force: 10 − 3 = 7 newtons. Buoyancy reduces the apparent weight of objects that have sunk completely to the sea floor. It is generally easier to lift an object up through the water than it is to pull it out of the water.
acceleration is the change in velocity over time. Because velocity is a vector, it can change in two ways: a change in magnitude and/or a change in direction. In one dimension, i.e. a line, acceleration is the rate at which something speeds up or slows down. However, as a vector quantity, acceleration is also the rate at which direction change. Acceleration has the dimensions L T−2. In SI units, acceleration is measured in meters per second squared (m/s2).
ReplyDeleteIn common speech, the term acceleration commonly is used for an increase in speed (the magnitude of velocity); a decrease in speed is called deceleration. In physics, a change in the direction of velocity also is an acceleration: for rotary motion, the change in direction of velocity results in centripetal (toward the center) acceleration; where as the rate of change of speed is a tangential acceleration. * Acceleration is a vector quantity which is defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity.
Sports announcers will occasionally say that a person is accelerating if he/she is moving fast. Yet acceleration has nothing to do with going fast. A person can be moving very fast and still not be accelerating. Acceleration has to do with changing how fast an object is moving. If an object is not changing its velocity, then the object is not accelerating. The data at the right are representative of a northward-moving accelerating object. The velocity is changing over the course of time. In fact, the velocity is changing by a constant amount - 10 m/s - in each second of time. Anytime an object's velocity is changing, the object is said to be accelerating; it has an acceleration.Acceleration due to gravity. This type of acceleration is given a special symbol, g. Since acceleration is a vector quantity, it has magnitude (size) and direction. On the surface of the Earth, the freely falling object has the following acceleration: g = -9.80 m/s2. Assuming there is no air resistance, all equations given in this section can be modified to apply to falling object, by simply replacing a with g.
The focal length of an optical system is a measure of how strongly it converges (focuses) or diverges (defocuses) light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus. A system with a shorter focal length has greater optical power than one with a long focal length; that is, it bends the rays more strongly, bringing them to a focus in a shorter distance.
ReplyDeleteIn telescopy and most photography, longer focal length or lower optical power is associated with larger magnification of distant objects, and a narrower angle of view. Conversely, shorter focal length or higher optical power is associated with a wider angle of view. In microscopy, on the other hand, a short objective lens focal length leads to higher magnification.
PRESSURE
ReplyDeletePressure is defined as force per unit area. It is usually more convenient to use pressure rather than force to describe the influences upon fluid behavior. The standard unit for pressure is the Pascal, which is a Newton per square meter.
For an object sitting on a surface, the force pressing on the surface is the weight of the object, but in different orientations it might have a different area in contact with the surface and therefore exert a different pressure.
here are many physical situations where pressure is the most important variable. If you are peeling an apple, then pressure is the key variable: if the knife is sharp, then the area of contact is small and you can peel with less force exerted on the blade. If you must get an injection, then pressure is the most important variable in getting the needle through your skin: it is better to have a sharp needle than a dull one since the smaller area of contact implies that less force is required to push the needle through the skin.
Pressure as Energy Density
ReplyDeletePressure in a fluid may be considered to be a measure of energy per unit volume or energy density. For a force exerted on a fluid, this can be seen from the definition of pressure:
The most obvious application is to the hydrostatic pressure of a fluid, where pressure can be used as energy density alongside kinetic energy density and potential energy density in the Bernoulli equation.
The other side of the coin is that energy densities from other causes can be conveniently expressed as an effective "pressure". For example, the energy density of solvent molecules which leads to osmosis is expressed as osmotic pressure. The energy density which keeps a star from collapsing is expressed as radiation pressure.
BERYLLIUM""""""""""""""""""""""""
ReplyDeleteberyllium is the chemical element with the symbol Be and atomic number 4.
A bivalent element, beryllium is found naturally only combined with other elements in minerals. Notable gemstones which contain beryllium include beryl (aquamarine, emerald) and chrysoberyl. The free element is a steel-grey, strong, lightweight brittle alkaline earth metal. It is primarily used as a hardening agent in alloys, notably beryllium copper. Structurally, beryllium's very low density (1.85 times that of water), high melting point (1278 °C), high temperature stability, and low coefficient of thermal expansion, make it in many ways an ideal aerospace material, and it has been used in rocket nozzles and is a significant component of planned space telescopes. Because of its relatively high transparency to X-rays and other ionizing radiation types, beryllium also has a number of uses as filters and windows for radiation and particle physics experiments.
Commercial use of beryllium metal presents technical challenges due to the toxicity (especially by inhalation) of beryllium-containing dusts. Beryllium produces a direct corrosive effect to tissue, and can cause a chronic life-threatening allergic disease called berylliosis in susceptible persons.
Beryllium is a relatively rare element in both the Earth and the universe. The element is not known to be necessary or useful for either plant or animal life.
Beryllium was discovered by Louis-Nicolas Vauquelin in 1798 as a component of beryl and in emeralds. Friedrich Wöhler[5] and Antoine Bussy independently isolated the metal in 1828 by reacting potassium and beryllium chloride. Beryllium's chemical similarity to aluminum was probably why beryllium was missed in previous searches
The name beryllium comes (via Latin: Beryllus and French: Béryl) from the Greek βήρυλλος, bērullos, beryl, from Prakrit veruliya (वॆरुलिय), from Pāli veḷuriya (वेलुरिय); veḷiru (भेलिरु) or, viḷar (भिलर्), "to become pale," in reference to the pale semiprecious gemstone beryl.[7] The original source of the word "Beryllium" is the Sanskrit word: वैडूर्य vaidurya-, which is of Dravidian origin and could be derived from the name of the modern city of Belur.[8] For about 160 years, beryllium was also known as glucinum or glucinium (with the accompanying chemical symbol "Gl"[9]), the name coming from the Greek word for sweet: γλυκυς, due to the sweet taste of its salts.
topic:Ideal gas law
ReplyDeleteThe Ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitations. It was first stated by Émile Clapeyron in 1834 as a combination of Boyle's law and Charles's law.[1] It can also be derived from kinetic theory, as was achieved (apparently independently) by August Krönig in 1856[2] and Rudolf Clausius in 1857.[3]
The state of an amount of gas is determined by its pressure, volume, and temperature. The modern form of the equation is:
where p is the absolute pressure of the gas; V is the volume of the gas; n is the amount of substance of the gas, usually measured in moles; R is the gas constant (which is 8.314472 J·K−1·mol−1 in SI units[4]); and T is the absolute temperature.
Since the angels it neglects both molecular size and intermolecular attractions, the ideal gas law is most accurate for monatomic gases at high temperatures and low pressures. The neglect of molecular size becomes less important for larger volumes, i.e., for lower pressures. The relative importance of intermolecular attractions diminishes with increasing thermal kinetic energy i.e., with increasing temperatures. More sophisticated equations of state, such as the van der Waals equation, allow deviations from ideality caused by molecular size and intermolecular forces to be taken into account.
CLARIZZA A. ISAAC
Gravitation
ReplyDeleteGravitation, or gravity, is a natural phenomenon by which objects with mass attract one another.[1] In everyday life, gravitation is most familiar as the agent that lends weight to objects with mass and causes them to fall to the ground when dropped. Gravitation causes dispersed matter to coalesce, thus accounting for the existence of the Earth, the Sun, and most of the macroscopic objects in the universe. It is responsible for keeping the Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around the Earth; for the formation of tides; for convection, by which fluid flow occurs under the influence of a density gradient and gravity; for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena observed on Earth.
Modern physics describes gravitation using the general theory of relativity, in which gravitation is a consequence of the curvature of spacetime which governs the motion of inertial objects. The simpler Newton's law of universal gravitation provides an accurate approximation for most calculations.
Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and early 17th centuries. In his famous (though possibly apocryphal)[2] experiment dropping balls from the Tower of Pisa, and later with careful measurements of balls rolling down inclines, Galileo showed that gravitation accelerates all objects at the same rate. This was a major departure from Aristotle's belief that heavier objects are accelerated faster.[3] Galileo correctly postulated air resistance as the reason that lighter objects may fall more slowly in an atmosphere. Galileo's work set the stage for the formulation of Newton's theory of gravity.
eugene garcia
collision
ReplyDeleteA collision is an isolated event in which two or more moving bodies (colliding bodies) exert relatively strong forces on each other for a relatively short time.
Collisions involve forces (there is a change in velocity). Collisions can be elastic, meaning they conserve energy and momentum, inelastic, meaning they conserve momentum but not energy, or totally inelastic (or plastic), meaning they conserve momentum and the two objects stick together.
Elastic and Inelastic Collisions
A perfectly elastic collision is defined as one in which there is no loss of kinetic energy in the collision. An inelastic collision is one in which part of the kinetic energy is changed to some other form of energy in the collision. Any macroscopic collision between objects will convert some of the kinetic energy into internal energy and other forms of energy, so no large scale impacts are perfectly elastic. Momentum is conserved in inelastic collisions, but one cannot track the kinetic energy through the collision since some of it is converted to other forms of energy. Collisions in ideal gases approach perfectly elastic collisions, as do scattering interactions of sub-atomic particles which are deflected by the electromagnetic force. Some large-scale interactions like the slingshot type gravitational interactions between satellites and planets are perfectly elastic. Collisions between hard spheres may be nearly elastic, so it is useful to calculate the limiting case of an elastic collision. The assumption of conservation of momentum as well as the conservation of kinetic energy makes possible the calculation of the final velocities in two-body collisions.
AMPERE
ReplyDeleteThe ampere was originally defined as one tenth of the CGS system electromagnetic unit of current (now known as the abampere), the amount of current which generates a force of two dynes per centimetre of length between two wires one centimetre apart. The size of the unit was chosen so that the units derived from it in the MKSA system would be conveniently sized.
The "international ampere" was an early realization of the ampere, defined as the current that would deposit 0.001118000 grams of silver per second from a silver nitrate solution.[10] Later, more accurate measurements revealed that this current is 0.99985 A.
The ampere (symbol: A) is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics. In practice, its name is often shortened to amp.
In practical terms, the ampere is a measure of the amount of electric charge passing a point per unit time. Around 6.242 × 1018 electrons passing a given point each second constitutes one ampere. (Since electrons have negative charge, they flow in the opposite direction to the conventional current.)
Ampère's force law states that there is an attractive force between two parallel wires carrying an electric current. This force is used in the formal definition of the ampere which states that it is the constant current which will produce an attractive force of 2 × 10–7 newtons per metre of length between two straight, parallel conductors of infinite length and negligible circular cross section placed one metre apart in a vacuum.
VELOCITY
ReplyDeleteVelocity
In physics, velocity is the rate of change of position. It is a vector physical quantity; both speed and direction are required to define it. In the SI (metric) system, it is measured in meters per second: (m/s) or ms−1. The scalar absolute value (magnitude) of velocity is speed. For example, "5 meters per second" is a scalar and not a vector, whereas "5 meters per second east" is a vector. The average velocity v of an object moving through a displacement (Δx) during a time interval (Δt) is described by the formula:
\bar{\mathbf{v}} = \frac{\Delta \mathbf{x}}{\Delta t}.
The rate of change of velocity is acceleration – how an object's speed or direction changes over time, and how it is changing at a particular point in time.
VELOCITY......
Quantity that designates the speed and direction in which a body moves. It can be represented graphically by an arrow (pointing in the direction of the motion), the length of which is proportional to the magnitude, or speed. For an object in circular motion, the direction at any instant is tangential to the circle at that point, and so is perpendicular to the radius at that point. The instantaneous speed of a vehicle, such as an automobile, can be determined by a speedometer, or mathematically by differential calculus. The average speed is the ratio of the distance traveled in any given time interval divided by the time taken.
nkkmiss aman to haha
ReplyDelete