Magnets are important for electric generators because spinning a magnet near a coil of wire produces electricity. For example, a wind turbine is using wind to spin the magnet, a hydroelectric facility does the same, but with the power of moving water. A magnet is characterized by its two poles; North and South. These poles create a magnetic field that flows from the North to the South pole, and can be depicted by a compass needle as shown in Figure 2.
A compass needle is actually a permanent magnet , and naturally orients itself to align with any magnetic field. Changing magnetic fields move create electric current near loops of wire. The ability for a material to respond to a magnetic field is discussed in more depth on hyperphysics.
Bismuth has been determined to have the strongest diamagnetism of all elements, but as Michael Faraday discovered in , it is a property of all matter to be repelled by a magnetic field. Diamagnetism is caused by the orbital motion of electrons creating tiny current loops, which produce weak magnetic fields, according to HyperPhysics. When an external magnetic field is applied to a material, these current loops tend to align in such a way as to oppose the applied field. This causes all materials to be repelled by a permanent magnet; however, the resulting force is usually too weak to be noticeable.
There are, however, some notable exceptions. Pyrolytic carbon, a substance similar to graphite, shows even stronger diamagnetism than bismuth, albeit only along one axis, and can actually be levitated above a super-strong rare earth magnet. Certain superconducting materials show even stronger diamagnetism below their critical temperature and so rare-earth magnets can be levitated above them.
In theory, because of their mutual repulsion, one can be levitated above the other. Paramagnetism occurs when a material becomes magnetic temporarily when placed in a magnetic field and reverts to its nonmagnetic state as soon as the external field is removed.
When a magnetic field is applied, some of the unpaired electron spins align themselves with the field and overwhelm the opposite force produced by diamagnetism. However, the effect is only noticeable at very low temperatures, according to Daniel Marsh, a professor of physics at Missouri Southern State University. Other, more complex, forms include antiferromagnetism, in which the magnetic fields of atoms or molecules align next to each other; and spin glass behavior, which involve both ferromagnetic and antiferromagnetic interactions.
Additionally, ferrimagnetism can be thought of as a combination of ferromagnetism and antiferromagnetism due to many similarities shared among them, but it still has its own uniqueness, according to the University of California, Davis. When a wire is moved in a magnetic field, the field induces a current in the wire.
Conversely, a magnetic field is produced by an electric charge in motion. A charge moving in a straight line, as through a straight wire, generates a magnetic field that spirals around the wire. When that wire is formed into a loop, the field becomes a doughnut shape, or a torus.
According to the Magnetic Recording Handbook Springer, by Marvin Cameras, this magnetic field can be greatly enhanced by placing a ferromagnetic metal core inside the coil. In some applications, direct current is used to produce a constant field in one direction that can be switched on and off with the current. This field can then deflect a movable iron lever causing an audible click. This is the basis for the telegraph , invented in the s by Samuel F.
Morse , which allowed for long-distance communication over wires using a binary code based on long- and short-duration pulses. Here are some articles about Magnetic Energy written for Universe Today. Listen here, Episode Magnetism Everywhere. Skip to content. Like this: Like Loading Next Post Next Carnival of Space
0コメント