A magnet is a material that has a magnetic field. "Magnet", the word, has Greek origins. It comes from the Greek "magnítis líthos", which means "magnesian stone". Magnesia is an area in Greece (Now Manisa, Turkey ) where deposits of magnetite have been found.
How magnet works:
All the magnetic fields are the result of moving charges. Through large currents in wires, electromagnets make fields. Permanent magnets produce fields through the orientation of the electron orbits and spins of the atoms in the magnet.
Magnetic fields are produced by moving charges. For instance, there are electrons when electricity flows through a wire. This movement through the wire produces a magnetic field around the wire. This can be replicated by wrapping a long wire around a metal object and connecting the wire to an electrical current. The wire around the metal produces a magnetic field and the metal becomes magnetized.
Magnets can be manufactured as well as occurring naturally. Examples of a permanent magnets are those magnetic calendars that real estate agents give you for your home. Natural magnetic materials are due to their atomic structure.
Magnets are commonly found in two forms: permanent magnets and electromagnets. Permanent magnets do not rely upon outside influences to generate their field where Electromagnets do require outside influences. Electromagnets rely on an electric current to generate a magnetic field. As the current increases, so does the magnetic field.
Magnetic fields are either attracted to or repelled by other materials. This force of attraction or repulsion is measured in newtons (SI units) or pounds force (US units). If a magnet is strongly attracted to something, then that something is said to have a high permeability. Two examples of materials with very high permeability are iron and steel. They are strongly attracted to magnets. An example of something with a low permeability is water. It is only weakly attracted to a magnetic fields. In fact, H2O has such a low permeability, it is actually repelled by magnetic fields. Everything in our world has a measurable permeability: people, air and even the vacuum of space.
Permanent magnets:
Matter is composed of protons, neutrons, and electrons, and all of these particles have the fundamental property of quantum mechanical spin. This spin gives each one of these particles a magnetic field. Because of this, and the fact that the average macroscopic piece of matter contains huge numbers of these particles, one might expect that all matter would have some magnetic field. However, this is not the case.
Inside each atom and molecule, the spin of each of particles is highly ordered as a result of the Pauli Exclusion Principle. But, there is no long range ordering of these spins. Without this long range ordering the result is no net magnetic field. That is because the magnetic moment of each of the particles is canceled by the magnetic moment of other particles.
Permanent magnets, though, are unique because this long range ordering does exist. And the highest degree of this ordering exists within magnetic domains. There is a strong reinforcing interaction between particles resulting in a great deal of order. Further, the greater the degree of ordering within these domains, the greater the resulting magnetic field will be. This is one of the hallmarks of a ferromagnetic material.
With respect to electrons, they play a primary role in generating a magnetic fields and magnets. Inside an atom, electrons exist either individually and also in pairs within any given orbit. When paired, the electrons in that pair always have an opposite spin. Spins have opposite orientation and this means that the two spins will cancel each other out. If electrons are all paired; then there is no net magnetic field generated.
Some atoms have electrons that are unpaired. Magnets have unpaired electrons, however, not all atoms that have unpaired electrons are ferromagnetic. For the material to be ferromagnetic, there be unpaired electrons present, and those unpaired electrons must interact with one another over long ranges in such a way that they are oriented in the same manner. This specific electron orientation of the atoms among other factors leads to the long range ordering required for a magnetic field. also, electrons can exist in an energy state that is lower when they have the same orientation.
Electromagnets:
At great distances, magnetic fields tend to obey an inverse square law. Translate, this implies that the strength of the field is inversely proportional to the distance from the center of magnet. Therefore, when the face of an electromagnet is engineered with a high degree of precision, it results in being able to get much closer to the surface that it is attempting to attract. In the case of any electromagnet, that is trying to attract an smooth and flat metal plate; if the face of the magnet is also smooth and also flat; then there will be more points of contact between the two. Also, the circuit will result in less resistance to the magnetic field.
Electromagnets are useful many ways. Examples are particle accelerators and MRI machines. If the electromagnet has enough strength; then force between nearby fields of wire can cause the electromagnet to be crushed by its own magnetic field.
Permanent Magnets:
Magnets have both a north pole and a south pole. This is a conceptual explanation to aid in discussing and describing magnets and how they work. These poles are not at specific locations.
To better explain this concept of pole, think of a group of pennies standing on their edge with heads facing in one direction forming one long line. If one were to divide the line of pennies into shorter lines, each of those shorter lines of pennies would still have a heads and a tails. Continue this without bounds.
Magnets are the same way. There is no particular place where all of the north poles or south poles meet. Also, splitting a magnet in half results in two magents. And both of those magnets will have its own north and a south pole. Those smaller magnets can then be divided, and all of the resulting pieces will have both a north and south pole. If the magnets continue to be split into smaller pieces; then there will be a size where the remaining pieces are just too small to hold a magnetic field. There are some materials that can be divided on the molecular level and still maintain a magnetic field.
Magnetic Field Of The Earth:
A naming system for the poles of magnets is a matter of standardization and is important. One normally associates the terms north pole and south pole to associate the earth's magnetic field. There are easy examples to demonstrate how suspending a magnet eventually results in an orientation that is north to south. This is because of the magnets attracts itself to the north and south magnetic poles of the earth. On the magnet, the end that points toward the Earth's geographic north is known as the north pole of the magnet and the end that points to the geographic south is the south pole of the magnet.
Types of permanent magnets:
Ceramic Magnets
Plastic Magnets
Alnico Magnets
Rare Earth or Neodymium Magnets, which are some of the most powerful permanent magnets
Samarium-Cobalt Magnets
Other Information On Magnets:
A magnet which is brought close to another magnet their fields will interact. Magnets of the same polarity will repel one another. Magnets of opposite polarity will attract each other. Magnets close ferromagnetic material, which is material not magnetized, will strongly attract to the material without regard to the orientation. The magnet will be attracted to the other item with equal strength from the poles. Diamagnetic materials weakly repel a magnetic field by definition. This will occur without regard to the orientation of the field. Also materials that are paramagnetic, by definition, are weakly attracted to a field that is magnetic field. This also occurs regardless of the orientation of the field that is magnetic.
Calculating the Magnetic Force:
Calculating the force between two magnets is depends on the shape, magnetization, orientation and separation of the magnets. A formula exists for the simple case of the force between two magnetic poles is:
F = [M1M2]/[U(R*)]
where
F = force
M = pole strength
U = the permeability of the intervening medium
R = the separation.
The contents of this site are for educational purposes only. Please contact us if you have questions. From Wikipedia, the free encyclopedia.