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

Two magnets, each of magnetic moment $‘M’ $ are placed so as to form a cross at right angles to each other. The magnetic moment of the system will be

The magnetic induction in air at a distance $d$  from an isolated point pole of strength $ m$  unit will be

The earth’s magnetic field at the equator is approximately $0.4 \;G$. Estimate the earth’s dipole moment.

The magnetic field to a small magnetic dipole of magnetic moment $M$, at distance $ r$  from the centre on the equatorial line is given by (in $M.K.S. $ system)