whate is the magnetostriction?
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Magnetostriction is a property of ferromagnetic materials to undergo a change of their physical dimensions when subjected to a magnetic field. This effect was first identified in 1842 by James Joule when observing a sample of nickel.\n\nThis property, which allow magnetostrictive materials to convert magnetic energy into kinetic energy and conversely, is used for the building of both actuation and sensing devices. It is often quantified by the magnetostrictive coefficient, L, which is the fractional change in length as the magnetization of the material increases from zero to the saturation value. The effect is responsible for the familiar "electric hum" ( Listen?) which can be heard near transformers and high power electrical devices (depending on country, either 100 or 120Hz, plus harmonics).\n\nThe reciprocal effect, the change of the susceptibility of a material when subjected to a mechanical stress, is called the Villari effect. Two other effects are related to magnetostriction: the Matteucci effect is the creation of a helical anisotropy of the susceptibility of a magnetostrictive material when subjected to a torque and the Wiedemann effect is the twisting of these materials when an helical magnetic field is applied to them.\n\nThe Villari Reversal is the change in sign of the magnetostriction of iron from positive to negative when exposed to magnetic fields of approximately 500 oersteds.
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Do you mean "magnetic"?????
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Metals become magnetized more easily than other materials because of the way in which their molecules bind to each other.  The positive nucleii align while the surrounding electrons (negatively charged) float around in a "sea of electrons."  Because magnetism is simply the attraction of positive charge to negative, anything can become magnetic, though it may take more work to break the electrons free of their orbits around the central positively charged nucleus.  The strength of magnetism is directly related to the amount of energy it takes to bring the electrons away from their positions around the nucleus.  In metals' case, it takes little.  In an MRI, it is actually water that is magnetized.
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Paramagnetism causes the substance to be attracted into the inducing magnetic field. It is associated with unpaired electrons.\n\nDiamagnetism causes the substance to be repelled from the inducing magnetic field. It is associated with paired electrons.
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In electromagnetism:--- \n--------------------------\n, permeability is the degree of magnetization of a material that responds linearly to an applied magnetic field. Magnetic permeability is represented by the Greek letter μ. This term was coined in September, 1885 by Oliver Heaviside. \n\nIn SI units, permeability is measured in henries per metre, or newtons per ampere squared. The constant value μ0 is known as the magnetic constant or the permeability of vacuum, and has the exact value  N·A-2.\n\nSome materials, called ferromagnetic or ferromagnets, are highly magnetic by nature, relative to most materials. They are composed of a large number of very small magnetic units working together called domains. Domains are not always aligned, and they often act against each other to reduce the strength of the net magnetic field.\n\nin Biology:-\n--------------\npermeability means allowing every thing to pass through it. if it so, then everything will be out of the cell and there will be no existance for the cell so, the cell membrane will be semi permeable or selectively permeable means allows the permeability of only selective melecules to pass through it.\n\nA semipermeable membrane, also termed a selectively permeable membrane, a partially permeable membrane or a differentially permeable membrane, is a membrane which will allow certain molecules or ions to pass through it by diffusion and occasionally specialised "facilitated diffusion". The rate of passage depends on the pressure, concentration and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute.\n\nDepending on the membrane and the solute, permeability may depend on solute size, solubility properties, or chemistry. An example of a semi-permeable membrane is a lipid bilayer, on which is based the plasma membrane that surrounds all biological cells. Many natural and synthetic materials thicker than a membrane are also semipermeable. An example of this is the thin film on the inside of an egg.\n\nSemipermeable membranes mostly exist on cells and in one's digestive tract.\n\nVascular permeability ------ characterizes the capacity of a blood vessel wall to pass through small molecules (ions, water, nutrients) or even whole cells (lymphocytes on their way to the site of inflammation). Blood vessel walls are lined by a single layer of endothelial cells. The gaps between endothelial cells (cell junctions) are strictly regulated depending on the type and physiological state of the tissue.
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First of all, I'm not professional of physical. I don't know at all, but Iron and steel are really high permeability, and strongly attract to magnet. Seem like the steel bar would tell you which one rely force electron. I don't think Iron has any thing to do with steel.
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Magnetism is an inherent property of a material or object, e.g. the earth.\n\nElectromagnetism is magnetism created by an electrical field - electromagnet - and these can be found all over the place - electrical relays, doorbells (check yours you will almost certainly find that it contains an electromagnet, etc.\n\nIn most cases when the current is turned off the electromagnetism goes.  However, it is possible to magnetise something permanently by use of electromagnetism.
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I've already answered this question and you might want to refer to that for more details. But here goes. \n\nA magnet is made of ferromagnetic materials, and will only attract ferromagnetic materials. These are iron, nickel and cobalt. Any alloy that contains one or more of those is ferromagnetic.\n\nThe metal forms tiny grains as it cools from a liquid to a solid, and within these tiny grains are even smaller regions called magnetic domains. Think of groups of atoms packed together. Unless a material is abolutely pure, there will be odd atoms of other elements and when the metal cools, they do not stack together absolutely correctly. If it is only a tiny amount of impurities, we do not notice the difference in terms of size, shape or weight.\n\nBut the domains are not lined up the same. Think of a bunch of guys just starting basic training. They are all milling around on the parade ground. But let's say that we heat the bar of metal until it is almost ready to melt and then subect it to a strong magnetic field (stick it inside the coil of a strong electromagnet, and let it cool that way.)\n\nNow they are all lined up the same way (just the way a bunch of paper clips will al line up when you pick them up with a magnet.) And when the metal cools and become solid once more, now they stay in that position. It is like a drill sergeant coming and yelling at the new recruits until they line up in formation. Now they are ready to take orders and get some useful work done.\n\nWhen the troops all line up and march the same way, you can see the result. They are more orderly, when they march along their feet all hit the ground at once, and they look unstoppable! \n\nIt is the same way with the magentic material. Each one of the individual atoms has its own magnetic field, but when they are all pointing in random directions, nothing useful can be done. Some are pointing one way, some the opposite way. They act against each other and their corporate effect cannot be felt.\n\nSo, now that the atoms within the domains are lined up together, and the metal has cooled and solidified into a solid bar again, the domains are lined up in formation. Now, they are all pointing in the same direction and we can feel the effects of the magnetic field even outside the magnet itself. The magnetic field reaches beyond the magnet and loops around in space until it reaches the other pole, forming a sort of circuit.\n\nOkay, now we have a magnet and we can understand why it attracts another magnet, because opposite poles attract. north attracts south and south attracts north. (No such thing as gay magnets! it's a law of nature!). \n\nBut why does it attract ordinary non-magnetized iron or steel?\n\nThat has to do with the fact that even though the metal is solid, and the atoms cannot flow away as in a liquid, the atoms are still free to rotate in place without moving from where they are.\n\nThink of the group of raw recruits before they go through their basic training. They are standing around. All of a sudden, they hear a loud noice. It is the drill sergeant yelling at them. All their heads turn in his direction! He has their attention. It is the same way with a magnet.\n\nWhen the magnetic field of a magnet acts on the atoms (iron, nickel or cobalt) of a piece of ferromagnetic alloy that has not yet been magentized, even though the atoms can't move from their spots, they rotate to face in the direction of the magnetic field. They temporarily act together, just as the domains inside the permanent magnet do. The fancy scientific name for this is 'magnetic induction'.\n\nNow, the temporary (induced) pole in the piece of metal is attracted to the permanent pole of the permanent magnet. They move together, because the tendency is for the magnetic field to travel as short a distance as possible, and a pole alwasy induces the opposite pole. The two together, so the magnetic field can travel across the shortest possible distance.\n\nWhen the
141111
Its like a microwave for metals, only kilohertz instead of gigahertz.  Its done with a coil instead of a magnetron.
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It lacks the crystalline electron structure that elements like magnesium and iron have. Thus, it cannot align into electrical dipoles, and is not magnetic.
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The force that a magnet exerts is proportional to 1/(r^2), where r is the distance of the object from the magnet. \n\nThe force = (1/(4*Pi*e0)*q1*q2)/(r^2)\nwhere q1,q2 are charges and e0 is a the permittivity of free space.
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ok, well, let's start with a basic description of magnetic materials.\n\nmagnetism has to do with the way electrons in a material interact with each other.  electrons have some basic properties (mass, charge, for example) and also a property called "spin".  \n\nit can be measured that any given electron has what is called a "magnetic dipole moment", which basically means that every electron behaves like a tiny bar magnet.  so the property of "spin" was devised to explain this - if you have some electric charge and move it around in a closed loop, a magnetic field is generated inside the loop.  this phenomenon is called induction and it's the basis for lots of real-life magnets.  this is why you usually see electromagnets made by wrapping wire around in a coil - when you pass an electrical current through the wire, the electrons in the metal basically move in a loop, and this causes a field to form.\n\nanyway, you can think of an electron as a little ball of electrical charge.  if the ball is spinning, then the charge on the ball is moving around in a circle - so this would create a magnetic field.  \n\nanother measurable property of this "spin" is that it is quantized - this means that the electrons can only spin at certain speeds and orientations.  different particles have different spins, and for an electron there are 2 spin states - usually referred to as "spin up" and "spin down" because the axis of the dipole moment points in different directions.\n\nthe difference between the various types of magnetic materials (ferromagnetic, antiferromagnetic, paramagnetic, etc) is in how the spins of all the electrons in the materials are oriented.\n\nin a ferromagnet, the spins are (mostly) oriented so that they're all pointing the same direction.  this causes the magnetic fields from each electron to add up, and you get a large macroscopic magnetic field as a result.\n\nin an antiferromagnet, on the other hand, spins are oriented so that neighboring electrons point in opposite directions.  this is a highly-ordered state, and in many materials only forms when you cool the substance below a critical temperature called the "neel temperature".  above this temperature the random thermal fluctuations take over and the spin ordering falls apart.\n\nantiferromagnetism is observed in transition metal compounds, in particular metal oxides, such as nickel oxide (NiO) or cobalt oxide (CoO).  the behavior of electronic spins are a subject of intense research these days, and so a simple and well-defined picture of their behavior is not easy to come by.  \n\nhowever, it is thought that the long-range interactions of electronic spin is responsible for a number of interesting effects that are being studied in transition-metal oxides.  one well-known example is in the study of high-temperature superconductors, which are often oxides of transition metal alloys.  the electrons involved in the superconducting effect act in pairs called "strongly correlated" electron pairs, and it is thought that the electrons interact via coupling through their spin.\n\nhere are some links so you can learn more:\n\nhttp://ghmfl.grenoble.cnrs.fr/magnetisme/recent5.htm\nhttp://www.jhu.edu/~gazette/2002/30sep02/30magnet.html\nhttp://www-als.lbl.gov/als/science/sci_archive/peem_spin.html\nhttp://en.wikipedia.org/wiki/Antiferromagnetism
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Magnetism is the property of magnetic materials to exert forces of certain objects, mainly iron and other magnetic materials; this force is known as the magnetic force.\n\nThe origin of this force is the movement of electrons or charged particles (ions) inside the materials.  When an electron spins around the atom's nucleus, according to the Biot-Savart Law it produces what we call a Magnetic Field, which exerts Magnetic Induction on it's surroundings.  Not only that, but also moving electrons in the surroundings of the original one (say, electrons of another object) will "feel" this induction as a force.\n\nSo, everything exerts a magnetic force on everything else, but the thing is that the magnetic induction and hence the direction of the force electrons in the surroundings will feel depend on the direction in which the original electron is moving (more specifically, on the vector Angular Momentum and/or the vector Magnetic Moment), and since there are lots of electrons moving in different directions in every material, the forces will point in every direction, cancelling themselves and producing a net force equal to zero.\n\nBut magnetic materials have the property of "aligning" the Angular Momentum/Magnetic Moments of all its atoms, and the forces produced by all its electrons (in the average) point in the same direction, producing the net force we feel when we put a magnet (magnetic material) near some piece of iron (a material susceptible to magnetism).\n\nHope I helped
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Iron is usually attracted to a magnet. If a bar of iron is magnetized, One end of the bar will attract one pole of the magnet, and repel the other pole of the magnet. \nCopper, nickel, and zinc are not magnetic. They neither attract or repel a magnet, and they cannot be magnetized.
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Different metals have different magnetic field strengths.\n\nFor example, neodymium magnets are among the strongest.
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>>Theory of magnetocrystalline anisotropy\n\nThe direction of a magnetization relative to body that supports it is determined mainly by two effects, shape anisotropy and magnetocrystalline anisotropy. The first arises from magnetostatic effects and the second from spin-orbit coupling between the spins and the lattice of the material. The magnetostatic effects can be calculated from micromagnetic calculations, but the magnetocrystalline anisotropy must be computed from the electronic structure of the material. This is an important quantity because it determines whether a magnetic material can be made into a good hard magnet, a good soft magnet or neither. Hard magnets are an essential component of electromagnetic motors and soft magnets are an essential component of transformers.<<\n\nThe rest of that quote can be found in the source link:
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Magnetism is actually a relativistic effect caused by moving charge. Current travelling in a wire has a magnetic field surrounding it. Bar magnets are special in that all the magnetic moments (the magnetic effect of electrons orbiting their nucleii) are aligned. In most materials the moments are randomly aligned and cancel each other out.