The distance between the poles of a horse shoe magnet is $0.1\, m$ and its pole strength is $0.01\, amp-m$. The induction of magnetic field at a point midway between the poles will be

Who has first used the properties of showing the direction of the magnet and why ?

The field due to a magnet at a distance $ R$  from the centre of the magnet is proportional to

The magnetic lines of force inside a bar magnet

Two points $A$ and $B$ are situated at a distance $x$ and $2x$ respectively from the nearer pole of a magnet $2\,cm$ long. The ratio of magnetic field at $A$ and $B$ is