Forces between magnetic poles

A magnet has two poles: a north pole, labelled N, and a south pole, labelled S. When two magnets are brought near each other, their poles exert forces on one another without touching.

The direction of the force depends on which poles face each other:

• Like poles repel: N and N, or S and S, push apart.
• Unlike poles attract: N and S pull towards each other.

Induced magnetism in magnetic materials

A magnetic material can be magnetised: it can acquire a north pole and a south pole. A non-magnetic material cannot be magnetised in this way. An unmagnetised piece of magnetic material does not have an overall north pole and south pole, even though it can become magnetised.

How a magnet induces magnetism

When a magnet is brought near a magnetic material, it can cause the material to become magnetised. This is called induced magnetism. The end of the material nearer the magnet becomes the opposite pole to the nearby pole of the magnet.

For example, if a magnet’s north pole is brought near a piece of unmagnetised magnetic material, the nearer end becomes a south pole and the farther end becomes a north pole. The opposite poles nearest each other attract, so the magnet attracts the material. If the magnet’s south pole is brought near instead, the nearer end becomes a north pole, so attraction still occurs.

Induced magnetism may be lost when the magnet that caused it is removed.

Magnetic field interactions

A magnet produces a magnetic field in the region around it. When another magnet is placed in that region, it experiences a magnetic force. Each magnet is in the field of the other, so each experiences a force.

The direction of the force depends on how the magnets are oriented. Each magnet has a north pole and a south pole:

• Unlike poles facing each other attract: the magnets pull towards each other.
• Like poles facing each other repel: the magnets push apart.

For example, if the north pole of one magnet faces the south pole of another, they attract. Turning one magnet around so that two north poles face each other changes the interaction to repulsion.