8.8 Domain Theory of Magnetism
It is observed that the magnetic field of a bar magnet is like the field produced by a solenoid carrying current. It suggests that all magnetic effects are due to moving charges. In the case of a solenoid, charges are moving in the wire. The motion responsible for the magnetism in a magnet is due to electrons within the atoms of the material.
An electron is a charged particle. Each electron in an atom is revolving about the nucleus and at the same time spinning about an axis through it. The rotation and spin both give rise to a magnetic field. Since there are many electrons in an atom, their rotations and spins may be so oriented to strengthen the magnetic effects mutually or to cancel the effects of one another. If an atom has some resultant magnetic field, it behaves like a tiny magnet. It is called a magnetic dipole.