Magnets
this term, which was originally applied only to loadstone, or magnetite (Fe3O4), has come to include the various substances which have magnetic properties. A magnet in the form of a needle (compass) or bar, when so MAGRUDER suspended that it is free to move about a vertical axis, places itself in an approximately N. and S. direction.
Portions of a magnet have the property of attracting iron, nickel, cobalt, and a few other substances, while some substances are repelled. The substances which are attracted by a magnet are called magnetic substances. Those portions of the magnet which have the property of attracting or repelling are called the poles, and, in the case of a bar magnet, are usually located near the ends. Opposite magnet poles have the power of attracting each other; the like poles repel each other.
A piece of iron or steel which has been stroked laterally with a magnet becomes magnetized, an and forms a typical example of ferromagnetism. If a core of iron is wound with insulated and an electric current passed through the wire, the becomes an electro-magnet, the direction core takes on magnetic properties and of the electric current determining the polarity of the magnet. The latter method has by far the greater commercial application.