The Theory behind Magnets and Magnetism

Hold a refrigerator magnet close to your refrigerator door. Let go of it. If you are close enough to the refrigerator, the magnet will jump across empty space and stick to the refrigerator. This action might seem kind of mysterious. But it makes sense when you know what magnetism is.

Magnetism is an invisible force. Magnetic force can attract (pull toward) or repel (push away). Magnetism comes from magnets. Magnets make things move without touching them. Some magnets are weak. Other magnets are much stronger.

Some rocks, such as lodestone, are natural magnets. Iron and some other metals can be made into magnets. Cloth, rubber, plastic, and many other things cannot be made into magnets.

SHAPES OF MAGNETS

Some magnets are shaped like the letter U. Some magnets are shaped like bars. Magnets can also be thin disks, squares, or rectangles. Other magnets are round or have irregular shapes.

Magnets can be big or small. Earth is a giant magnet. The Sun, stars, and some other planets are also magnets. Atoms can be magnets. Atoms are tiny bits of matter much too small to see.

NORTH AND SOUTH POLES

The important thing to remember about a magnet is that it has two ends called poles. One end is called the North Pole, and the other end is the South Pole. The south pole of one magnet will attract and stick to the north pole of another magnet. The south pole of a magnet will repel, or push away, the south pole of another magnet. North poles will also repel each other.

MAGNETIC FIELDS

Hold the north pole of one magnet close to the south pole of another magnet. Don’t let them touch. You can feel the magnets tugging toward each other. Now try to bring the north poles of both magnets together. You can feel the magnets pushing away from each other.

Magnets are surrounded by magnetic fields. You feel magnetic pull or push inside the magnetic field. Move the magnets farther apart. The pull feels weaker. The farther you go from a magnet, the weaker its magnetic force becomes. Magnetic fields are strong close to a magnet and weak far away. If you hold the magnets far enough from each other, you will not feel them pull at all.

MAKING A MAGNET

Long ago, people in Greece, Rome, and China found that lodestone could pull iron toward it. Lodestone is made of the mineral magnetite. When they rubbed a piece of iron with lodestone, the iron became a magnet, too. People in ancient times did not know it, but rubbing made tiny magnets inside the iron all line up in the same direction. All the north poles were pointed the same way. So were the south poles.

In the 1200s, sailors learned how to make a compass that could help them find their way at sea. They made a needle from a thin piece of lodestone or iron. They hung the needle from a string. The needle always pointed north. Because Earth is a big magnet, the south pole of the compass needle always points toward the magnetic North Pole of Earth. Remember, the south pole of one magnet always pulls toward the north pole of another magnet. This works whether the magnet is as small as a needle or as big as a planet.

In the 1800s, people learned that magnetism is related to electricity. They learned how to make magnets by winding electric wire around a piece of iron. These magnets are called electromagnets.