magnets

MAGNETS
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Some irons, when dug up, attract other metals.
They are called MAGNETS.
The reason that they are magnetic is that their DOMAINS are aligned.

One end of a bar magnet is the NORTH POLE, the other end the SOUTH POLE.

A rule of magnetism is that LIKE POLES REPEL, UNLIKE POLES ATTRACT.
North attracts South and repels North etc.
The North pointer on a compass is actually a South pole since it is attracted by the North pole of the earth.

A magnet is surrounded by an invisible MAGNETIC FIELD made of magnetic LINES OF FORCE.
These lines of force can be made visible by covering a magnet with a sheet of paper and sprinkling iron filings on the paper.

The lines of force run from north to south.

Lines of force pass through all materials including insulators.
They pass through some more easily than others.
These are said to have a lower RELUCTANCE.
Iron has a lower reluctance than air.
The lines of force prefer to pass through lower reluctance materials.

PERMANENT magnets are made of steel or steel alloys. Brass, copper and aluminium do not magnetise.