# Magnetism

## Magnetism

Magnetism is the property displayed by magnets and produced by the movement of electric charges, which results in objects being attracted or pushed away.
» Magnet is a piece of iron or other materials that can attract iron containing objects and that points north and south when suspended.
» A magnet is characterized by following two properties :
1. Attractive property : A magnet attracts magnetic substances like iron, cobalt, nickel and some of their alloys like magnetite.
2. Directive property : When a magnet is freely suspended, it aligns itself in the geographical north south direction.

» A magnet may be :
1. Natural : Natural magnet is oxide of iron. But due to irregular shape, weak magnetism and high brittleness, natural magnets find no use in the laboratory.
2. Artificial : The magnets made by artificial methods are called artificial magnets or man made magnets. They may be of different types like bar magnet, horse shoe magnet, Robinson's ball ended magnet, magnetic needle, electromagnet etc.

» The two points near the two ends of a magnet where the attracting capacity is maximum are called magnetic poles. When a magnet is freely suspended, its one pole always directs towards the north. This pole is called north pole. The other pole is called south pole.
» The imaginary line joining the two poles of a magnet is called magnetic axis of the magnet.
» Simi lar poles repel each other and dissimilar poles attract each other.
» When a magnetic substance is placed rear a magnet, it gets magnetized due to induction.

## Magnetic Field

Region in space around a magnet where the magnet has its magnetic effect is called magnetic field of the magnet.

## Intensity of magnetic field or magnetic flux density

Magnetic flux density of a magnetic field is the force experienced by a north pole of unit strength placed at the point. It S.I. Unit is newton/ampere-meter or weber/meter2 or tesla.

## Magnetic line of force

The magnetic lines of force are imaginary curves which represent a magnetic field graphically . The tangent drawn at any point on the magnetic lines of force gives the direction of magnetic field at that point.

Properties of magnetic line of force :
1. Magnetic lines of force are closed curves. Outside the magnet they are from north to south pole and inside the magnet they are from south to north pole.
2. Two lines of force near intersect each other.
3. If the line of force are crowded, the field is strong.
3. If the line of force are crowded, the field is strong.
4. If the liens of force are parallel and equidistant, the field is uniform.