Magnetism is an aspect of electromagnetism, one of the fundamental forces of nature. Magnetic forces are produced by the motion of charged particles such as electrons, indicating the close relationship between electricity and magnetism. The unifying frame for these two forces is called electromagnetic theory. The most familiar evidence of magnetism is the attractive or repulsive force observed to act between magnetic materials such as iron. More subtle effects of magnetism, however, are found in all matter. In recent times these effects have provided important clues to the atomic structure of matter.
Numerous applications of magnetism and of magnetic materials have arisen in the past 100 years. The electromagnet, for example, is the basis of the electric motor and the transformer (Lawrence et al 1998). In more recent times, the development of new magnetic materials has also been important in the computer revolution. Computer memories can be fabricated using bubble domains. These domains are actually smaller regions of magnetization that are either parallel or antiparallel to the overall magnetization of the material. Depending on this direction, the bubble indicates either a one or a zero, thus serving as the units of the binary number system used in computers. Magnetic materials are also important constituents of tapes and disks on which data are stored.
In addition to the atomic-sized magnetic units used in computers, large, powerful magnets are crucial to a variety of modern technologies (Lawrence et al 1998). Powerful magnetic fields are used in nuclear magnetic resonance imaging, an important diagnostic tool used by doctors. Superconducting magnets are used in today's most powerful particle accelerators to keep the accelerated particles focused and moving in a curved path. Scientists are developing magnetic levitation trains that use strong magnets to enable trains to float above the tracks, reducing friction (Null, 1998).
Magnetism.....
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