Magnets Lodestone Magnesia The oldest known writing about

Magnets

“Lodestone” Magnesia The oldest known writing about lodestones was by Thales of Miletus in about 600 BC.

THE LETTER OF PETRUS PEREGRINUS ON THE MAGNET, A. D. 1269 In 1269 A. D. , a French scientist named Petrus Peregrinus de Maricourt wrote a letter that describes the properties of lodestones (or magnets) which he had discovered during his experiments.

What properties of magnets can YOU discover by doing your own experiments?

Recording Results of your Experiments “It works” or “It Doesn't Work” The light bulb lights when the aluminum wire is used in the circuit. The light bulb does not light when the plastic wire is used in the circuit. The light bulb does not light when the string is used in the circuit. OR Type of Wire The bulb lights The bulb does NOT light Copper x Aluminum x Plastic x String x

Let’s compare your observations to what Petrus Peregrinus wrote about magnets nearly 750 years ago.

CHARACTERISTICS OF A GOOD LODESTONE Magnets attract things made of iron. photo credit: R. Weller/Cochise College

HOW TO DISTINGUISH THE POLES OF A LODESTONE There are two points on opposite sides of the magnet called “poles”. • Bits of iron are attracted most strongly at these points. • A small piece of iron shaped like a needle will stand straight up at these two points.

HOW TO TELL WHICH IS NORTH AND WHICH SOUTH When a magnet is free to move, the north pole of the magnet will turn around until its north pole is pointing north.

HOW ONE LODESTONE ATTRACTS ANOTHER The north pole of one magnet attracts the south pole of another, and the south pole attracts the north. N S Two north poles or two south poles repel each other. S N N S S N

HOW IRON TOUCHED BY A LODESTONE TURNS TOWARDS THE POLES OF THE WORLD A magnet touching a piece of iron can turn the iron into a temporary magnet.

WHY THE NORTH POLE OF ONE LODESTONE ATTRACTS THE SOUTH POLE OF ANOTHER AND VICE VERSA N S When a magnet is cut into smaller pieces, . . .

WHY THE NORTH POLE OF ONE LODESTONE ATTRACTS THE SOUTH POLE OF ANOTHER AND VICE VERSA N S When a magnet is cut into smaller pieces, each smaller piece has both a north and south pole.

Summary – Properties of Magnets • Magnets attract iron (also nickel and cobalt). • There are two points on opposite sides of the magnet called “poles”, where metals are attracted most strongly. • When a magnet is free to move, the north pole will turn to point north. • Opposite poles attract, like poles repel • A magnet touching a piece of iron can turn it into a temporary magnet. • When a magnet is cut into smaller pieces, each smaller piece has both a North & South pole.

Do magnets need to touch a piece of iron or another magnet to exert a magnetic force on the iron or other magnet?

There is a disturbance in the space around a magnet called a magnetic field.