# Magnetism

Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field.

## MAGNETIC FIELD

The region or area around a magnet in which it can attract other small pieces of iron is called magnetic field.

Magnetic field consists of invisible and imaginary lines emitting from the North Pole and terminating at South Pole these lines are called magnetic lines of force. That travels from north to south in the atmosphere and from south to north inside the magnet, there for they form a close loop.

## MAGNETIC FLUX OF ELECTRIC CURRENT MAGNET

It is a piece of iron or metal, which can attract other small piece of iron.

## LAW OF MAGNETIC FORCE

Coulomb was the first scientist who determinate experimentally the quantitative expression for the magnet forces between two magnetic poles. He found that the force between two magnetic poles place in a medium is

- Directly proportion to their pole strength
- Inversely proportion to the square of the distance between them.
- Inversely proportion to the absolute permeability of the medium. For example let ml and m2 are the magnetic strength of two poles and "r" is the distance between them and "
**υ**" is the permeability of the medium of the force between poles will be given the fallowing expression

.

F ∝ m_{1}m_{2}

υr^{2}

F = K m_{1}m_{2}

υr^{2}

Where "K" is constant of proportionality whose values depends upon the system of units in "MKS" system, the values of "K" is

If the two poles are placed in vacuums or air then Where υ_{o} is the absolute permeability of vacuum, air and its value given by

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