Magnetic phenomena were first observed at least 2500 years ago in fragments of magnetized iron ore found near the ancient city of Magnesia (now Manisa, in western Turkey). These fragments were examples of what are now called permanent magnets. Permanent magnet were found to exert forces on each other as well as on pieces of iron that were not magnetized. It was discovered that when an iron rod is brought in
13
Magnetism
contact with a natural magnet, the rod also becomes magnetized. When such a rod is floated on water or suspended by a string from its center, it tends to line itself up in a north-south direction, which we called the poles of the magnet. The magnetic has two poles, called northand south poles, which exhibit forces on each other; that is, like poles repel each other and unlike poles attract each other.