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History of Magnets

Magnets have been known since ancient times. Their form in nature manifests as magnetized bits of stone, actually an iron ore called magnetite. Such stones could pick up small pieces of iron. It was discovered that iron nails or needles stroked with these stones would become magnetized too, as would iron bars that were laid north-to-south while being hammered and cooled after being heated in a forge.

If a small magnet were suspended on a thread or floated on a cork in a bowl of water, people found that the magnet would turn with one end pointing in a northern direction. This discovery of the compass was simply made of a magnet supported so that it could turn freely. Around 1600, people realized that a compass points north-and-south because the earth itself is magnetic, with a field that approximately lines up with the geographic north and south poles. (The earth’s north magnetic poles lies in northern Canada, and its south magnetic pole is off the coast of Antarctica.)

By the mid-1700’s, a connection between electricity and magnetism was suspected by a number of scientists, including Ben Franklin. Perhaps because magnetic forces do not interact with static electric charges or fields, and because the force between magnets and moving charges or currents is not aligned with the electric motion or current but at right angles to it, numerous people looking for electromagnetic interactions did not find them for several decades. Eventually the relation was found by Hans Christian Oersted in 1820, while he was demonstrating the electric heating of a wire. He noticed that a compass responded to the electric current passing through a nearby wire (see http://www.phy6.org/earthmag/oersted.htm).

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