The current is flowing through solenoid, then solenoid acting as what ?

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

The $ S.I.$  unit of magnetic permeability is

Two short magnets with their axes horizontal and perpendicular to the magnetic meridian are placed with their centres $40\, cm$  east and $ 50\,cm$  west of magnetic needle. If the needle remains undeflected, the ratio of their magnetic moments ${M_1}:{M_2}$ is

A short bar magnet of magnetic movement $5.25 \times 10^{-2} \;J\, T ^{-1}$ is placed with its axis perpendicular to the earth's field direction. At what distance from the centre of the magnet, the resultant field is inclined at $45^{\circ}$ with earth's field on

$(a)$ its normal bisector and

$(b)$ its axis.

Magnitude of the earth's field at the place is given to be $0.42 \;G$. Ignore the length of the magnet in comparison to the distances involved.