Magnetism is a property of materials that respond at an atomic or subatomic level to an applied 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.
It is a piece of iron or metal, which can attract other small piece of iron.
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
F = K m1m2
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 υo is the absolute permeability of vacuum, air and its value given by