Magnets are usually made of iron or steel. Pieces of metal, like small nails and pins, stick to them as though they are glued. Magnets are made in factories, but did you know that there are many rocks which are magnetic?
More than 2000 years ago the Greeks knew about a particular king of stone which ahd the same strange power. A great deal of this stone came the district of Magnesia. The people living there were called Magnetes, which explains why the word "magnet" is used today.
These people also knew that when the stone was allowed to swing freely, it would always point in the same direction.
The Chinese also used the same kind of stone for guiding people who were travelling long distances. Because of the help they gave to travellers, these stones were called lodestones, meaning leading stones.
Like lodestone, a magnet which is allowed to swing freely will always point in a North - south direction. Because of this, the two ends of the magnet are called the North Pole and the South Pole.
If you try to put the North Poles of two bar magnets together, you will feel a force trying to keep them apart. The two South Poles will repel each other in the same way.
But the North Pole of one magnet near the South Pole of another magnet will attract to each other. All magnets behave in the same way. Thus, we say that "LIKE POLES REPEL AND UNLIKE POLES ATTRACT".
"All things are made of atoms, and every atom is like a magnet."It a piece of iron or steel is stroked from one end to the other with a magnet the atoms in the iron or steel line up. The magnetism of every atom now adds together to make one stronger magnet.
The same thing happens if an iron bar is wrapped around with a wire carrying an electric current. It becomes an electro-magnet that can hold great weights. The weight falls when the flow of electricity is switched off.
These kinds of magnets are often used in breakers' yards for smashing up old cars and machinery.
The atom-smasher uses a huge circular magnet weighing many thousand of tons. Scientists invent machines like this to help them find out more about the atom.
A compass is useful to travellers because its needle always points to the North. This needle is just a tiny swinging magnet.
Why does a swinging magnet take up a North - South direction? It is because the Earth itself is a big magnet. It turns about an axis through the North and South Poles. It behaves as if it had a huge bar magnet more or less along this axis. But scientists could not explain how the earth became magnetised. Just like the Earth, many stars have magnetism.
Every few years a number of dark spots appear on the Sun. They can often be seen by looking at the Sun through special dark glasses. Remember, you must never look at the Sun without using darkened glasses as its light rays will harm your eyes.
By examining the light sent out by the atoms near the sunspots, the scientists know that these atoms have been affected by magnetism.
A great many things about the atoms and molecules can be found out by putting them near a strong magnet.
Using rockets and satellites, scientists are exploring the magnetism of other planets. Even in the outer space there are magnetic forces.