Magnetism

Magnet: the term magnet is derived from magnetite (Fe3O4) which is an ore of iron.

Any substance which possesses the following two properties is called a magnet.

1. It attracts small pieces of iron towards itself.

2. When suspended freely, it always comes to rest in the north-south direction.

Natural and artificial magnets:

Lode stone and Magnetite are natural magnets because they are found in nature.

Artificial magnets are prepared by man to be used at any time and at any place. These magnets are much stronger than lode stone.

Example: soft iron

Magnetic and non magnetic substances:

Substances which are attracted by a magnet are called magnetic substances.

Example: Iron, Cobalt, Nickel etc.

Substances which are not attracted by a magnet are called non-magnetic substances.

Example: paper, cloth

Properties of magnets

Poles of a magnet: The two ends of a magnet where the magnetic force is greatest are called poles of magnet. Each magnet has two poles. The end of the magnet that points towards the north is called North Pole. And the other end of the magnet pointing towards the south is called South Pole.

Like poles repel, unlike poles attract.

For Example take two bar magnets. Suspend one magnet with a piece of thread. It will come to rest in the north-south direction. Hold the other magnet in your hand and bring its north pole near the north pole of the suspended magnet. You will find that the north pole of the suspended magnet is repelled that is North Pole moves away.

Now bring the south pole of the magnet in the hand of the north pole of the suspended magnet. You will find that the north pole of the suspended magnet will be attracted towards the south pole of other magnet. This states that like poles repels and unlike poles attract.

Magnetic poles always exist in pairs:

If a bar magnet is broken into two pieces you will see that each piece behaves as a whole magnet. This shows that new poles are formed at the broken ends.

If these pieces are further broken into smaller pieces, each piece behaves as a whole magnet with two opposite poles.

Thus, we see that even the smallest piece of magnet has north and south poles and we cannot separate the two poles.Therefore we conclude that Magnetic poles always exist in pairs