Magnetism

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Magnetic lines of force of a bar magnet shown by iron filings on paper

In the field of physics, magnetism is a force by which objects attract or push away other materials.

Magnetism can be seen in special objects called magnets. When magnets are placed near objects that are magnetic, the magnet will attract the object and pull it to the magnet. Magnets can also push away other objects. The most common objects that are attracted to magnets contain iron or steel. Most other metals, including aluminum, are not attracted to magnets.

Magnets have an area, or distance, around them called a magnetic field. Objects inside the magnetic field can be attracted to the magnet. Objects outside the magnetic field will not be attracted to the magnet. This is why a magnet must be placed close to an object to attract it.

The ends of a magnet are called poles. This is where the force of a magnet is the strongest. All magnets have a north pole and a south pole. If a magnet is allowed to spin, then the north pole of a magnet will always point to the north pole of the Earth. The south pole of a magnet will point to earth's south pole. You can try this yourself by tying a string to a bar magnet and then holding the string so that the magnet can turn.

Like poles of two magnets always push away, or repel, each other. Different poles attract each other. For example, if the south pole of one magnet is put near the south pole of another magnet, the magnets will push away from each other. This will also happen with two north poles. But if a north pole is put near a south pole, the magnets will move toward each other until they stick together.

Magnets have many uses. One use was discovered long ago when explorers found out a magnet could be used as a compass to show the locations of the poles on the Earth.

Electromagnets are another kind of magnet that only work when electricity is running through them.