Properties of magnets

Bar magnets are permanent magnets. This means that their magnetism is there all the time and cannot be turned on or off as it can with electromagnets.

Bar magnets have two poles:

  • north pole – normally shown as N
  • south pole – normally shown as S

Opposite (unlike) poles attract, and like poles repel.

A bar magnet, with the north and south poles marked red and blue.

If permanent magnets are repeatedly knocked, the strength of their magnetic field is reduced. Converting a magnet to a non-magnet is called demagnetisation.

Magnets are made from magnetic metals – iron, nickel and cobalt. These are the only pure metals that can be turned into a permanent magnet. Steel is an alloy of iron and so can also be made into a magnet.

If these metals have not been turned into a permanent magnet they will still be attracted to a magnet if placed within a magnetic field. In this situation they act as a magnet - but only whilst in the magnetic field. This is called induced magnetism.

Substances that can be permanently magnetised are described as magnetically hard. These are often alloys of iron, nickel and cobalt.

Substances that can only be temporarily magnetised are described as magnetically soft. Alloys with less iron, nickel or cobalt will be magnetically soft and have a weaker magnetic field. Alloys of iron are called ferrous and those without iron are called non-ferrous.

Testing magnets

You can’t test what a magnet is attracted to, but you can test what it repels. Objects that are made of unmagnetised iron, cobalt and nickel are attracted to either pole of a magnet, but not repelled. You can only show that an object is a magnet if it repels another magnet.