Molecular Theory Of MagnetismThe basic points of the theory are as follows:
- Each molecule of a magnetic substance is a complete magnet.
- In an un-magnetised substance the molecular magnets are arranged randomly and form closed chains. Hence, the magnetic effect of any one of them is cancelled by its neighbour. So the entire bar does not exhibit any net magnetic property with distinct N and S poles.
Randomly Arranged Molecular Magnets
- When a substance is magnetised, all the tiny molecular magnets arrange themselves in parallel lines. As a result one end becomes the north pole and the other becomes the south pole.
Magnetic Domains Aligned in NS Direction
- When this magnetised substance is heated or hammered, the molecular magnets get kinetic energy and the straight chains get disturbed and the molecules go back to the original random distribution, thus losing the magnetic properties.