MAGNETISM 1 INTRODUCTION History of magnetism 2 Laws

MAGNETISM 1 • INTRODUCTION • (History of magnetism) 2 • Laws of magnetism • (Important four properties) 3 • Artificial magnet • (Electrical methods)

History Of Magnetism During 600 BC an ore was discovered which had the property of attracting small pieces of iron. This ore was a black oxide of iron called magnetite.

PROPERTIES OF A MAGNET � 1 Attractive property- A magnet can attract certain material like iron nickel cobalt etc. � These attractive properties are concentrated at the ends of a magnet called poles

2 Directive property (lodestone) � 2 When a magnet is freely suspended it always orient along north south direction.

3 Poles exist in pairs If a long magnet is broken into two pieces, each piece is found to be an individual magnet having its own pair of opposite poles at its two ends. �

4 THE LAW OF MAGNETISM � Like pole repel and unlike poles attract each another.

CLASSIFICATION OF MATERIALS � Materials Magnetic (Iron, nickel, cobalt ) (copper, brass, aluminium) � Non magnetic

1. Single touch method 2. Divided touch method

3. By electric current

SUMMARY 1 The substance which has the property to attract small pieces of iron and of setting along a definite direction when suspended freely , is known as magnet. 2 When a magnet is suspended freely, it always sets in north south direction. 3 The point on magnet where the attraction appears to be maximum are called poles. 4 Like poles repel each other while unlike poles attract each other. 5 Poles exist in pairs. 6 Magnetisation can be done either by single touch , double touch or by electrical method 7 Materials are classified in to two, magnetic and non-magnetic.