Introduction
All magnets have two poles, a north-seeking end of the North Pole and a south-seeking end or the 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 of its 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 the iron 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 a magnet from a height.
Electro-Magnetic Forces
Electromagnetic force can be attractive or repulsive but the gravitational force is always attractive.
EM force is stronger than the gravitational force.
The nuclear force is 100 times stronger than the EM force but the range is less.
Gravitational force doesn’t need an intervening medium.
The magnetic field produced by a current in a conductor decreases as the distance from it increases.
The right-hand thumb rule gives the direction of the magnetic field due to the current in a conductor. The Thumb points in the direction of the current and curled fingers point in direction of the magnetic field.
Miscellaneous
The magnetic field is produced even by the weak electrical impulses of our nerve cells. A significant magnetic field is present in the 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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