Chapter 21: MAGNETISM


All magnets have two poles, north seeking end or North Pole and south seeking end or South Pole.

Magnetic – Materials attracted towards a magnet [iron, nickel, cobalt]

Non magnetic – Materials that are not attracted towards a magnet.

A freely suspended bar magnet always rests in the North South direction.

Take a rectangular piece of iron. Place it on the table. Now take a bar magnet and place one ofits poles near one edge of the bar of iron. Without lifting the bar magnet, move it along the length of the iron bar till you reach the other end. Now,lift the magnet and bring the pole (the same pole you started with) to the same point of the iron bar from which you began. Move the magnet again along theiron bar in the same direction as you did before.  Repeating these several caused the iron bar to become a magnet.

In magnetism, similar poles repel and opposite poles attract each other.

Magnetism can be lost by heating, hammering or dropping magnet from a height.

Electro-Magnetic Forces

Electromagnetic force can be attractive or repulsive but gravitational force is always attractive.

EM force is stronger than gravitational force.

Nuclear force is 100 times stronger than EM force but range is less.

Gravitational force doesn’t need an intervening medium.

Magnetic field produced by a current in a conductor decreases as the distance from it increases.

Right hand thumb rule gives the direction of magnetic field due to current in a conductor. Thumb points in the direction of current and curled fingers point in direction of magnetic field.


Magnetic field is produced even by the weak electrical impulses of our nerve cells. Significant magnetic field is present in brain and heart. The magnetic field produced by the body is the basis of MRI scans that get images of body parts.


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