Magnetism and Matter

Notes

Magnetism and Matter

1. Magnet

A substance which has two opposite poles separated by a distance and has directive, attractive and inductive properties is called a magnet.

A substance that attracts metallic and current-carrying substances is called a magnet.

2. Types of Magnet

1. Natural Magnet
2. Artificial Magnet

Natural Magnet

The magnet which is found in nature and has permanent magnetic properties is called a natural magnet.

• Example: Lodestone
• Lodestone is found in black and brownish colour.
• Lodestone has heavy mass.
• Lodestone is also known as black stone, leadstone and kissing stone.

The chemical formula of lodestone is Fe₃O₄.

Fe₃O₄ is an iron ore called magnetite, and hence lodestone is named as a magnet.

Magnet originated from one magnetite, and its written proof is found in a book named De Rerum Natura.

Fe₃O₄ means:

FeO · Fe₂O₃

It means Fe₃O₄ has one ferrous and two ferric ions.

Artificial Magnet

The magnet which is made by humans and has magnetic properties is called an artificial magnet.

It is prepared by:

1. Solenoid
2. Toroid
3. Ferrous material
4. Steel/Cobalt

3. Magnetisation

The process of producing magnetic properties in a substance is called magnetisation.

Ways of Magnetisation

1. By passing current
2. Rubbing with a magnet

4. Demagnetisation

The process of removing the magnetic properties from a substance is called demagnetisation.

Ways of Demagnetisation

1. By heating
2. By hammering
3. By throwing

5. Properties of a Magnet

We discuss three properties of a magnet:

1. Directive property
2. Attractive property
3. Inducing property

Directive Property

When a magnet is suspended freely by a thread, it points or aligns itself towards the north-south direction. This property is known as the directive property of a magnet.

Attractive Property

When a magnet is brought near metallic substances or a current-carrying wire, the magnet is repelled or attracted by that substance. This property of a magnet is known as the attractive property of a magnet.

Inducing Property

When magnetic material is attracted by a magnet, magnetic properties are induced in that substance. This property of a magnet is known as the inducing property.

6. Poles of a Magnet

The poles of a magnet cannot be isolated.