The study of electromagnetism began over 2,000 years ago with the ancient Greek philosopher Thales's (624-546 b.c.) discovery that when amber (elektron in Greek) was rubbed, it was able to pick up lightweight objects. Lodestone, found in the region of Magnesia, could also attract iron, but without being rubbed. The connection between the attractive abilities of the two materials did not occur to the ancients.

During the eleventh century, the Chinese learned that a freely suspended magnetized needle had the ability to point almost due north. Although the device was used as a compass to show direction, it was not known that cause of the phenomenon was the Earth 's magnetic field.

In 1269, the little-known French scholar Petrus Peregrinus (born c.1240) described how to determine the north and south poles of a magnet: Like poles repelled, and opposite poles attracted. Breaking a magnet in half did not isolate...