WEBER'S THEORY OF MAGNETISM

The fact that north and south poles appear on either end of a piece on breaking a magnet and also various other phenomenon associated with magnetization of iron led Wilhelm Weber to suggest that 

"Each molecule of a magnetic substance is a tiny magnet with opposite polarities at its two ends".

Owing later expanded Weber's Theory and said that under ordinary conditions, in an unmagnetised state, a substance has number of such tiny magnets grouped together in a haphazard way such that these magnets form a closed chain, so that the various north and south poles neutralize one another and thus produce no external magnetic field.

Loose and Random
 Magnetic Domains

On applying a magnetizing force, these closed chains are broken up, the small magnets to align themselves in such a manner that there axes become parallel and their north poles all point to one direction and south poles to the opposite direction.

Effect of Magnetisation
Domains Lined-up in Series

Within the magnet however, each north-pole is neutralized by the adjacent south-pole and hence no net magnetism is available in the body of the magnet.

This theory offers a very satisfactory explanation of a large number of magnetic phenomenon such as induction, magnetization by rubbing, magnetic saturation, equality of strength of north and south poles, hysteresis, demagnetization due to rough handling, and magneto-striction, etc.