$A$ magnet of magnetic moment $M$ is situated with its axis along the direction of a magnetic field of strength $B$. The work done in rotating it by an angle of $180^{\circ}$ will be

$A$ magnetic needle lying parallel to a magnetic field requires $W$ units of work to turn it through $60^{\circ}$. The torque required to maintain the needle in this position will be

Two short magnets are placed along the same axis with their like poles facing each other. They repel each other with a force which varies inversely as:

The figure shows a bar magnet and a long straight wire $W$,carrying current into the plane of the paper. Point $P$ is the point of intersection of the axis of the magnet and the line of shortest distance between the magnet and the wire. If $P$ is the midpoint of the magnet,then which of the following statements is correct?

The magnetic moment of a short magnet is $16 \ Am^2$. The magnetic induction at a point $20 \ cm$ away from its midpoint on $(i)$ axial point and $(ii)$ equatorial point respectively,will be:

$A$ magnetic needle suspended parallel to a magnetic field requires $\sqrt{3} \, J$ of work to turn it through $60^{\circ}$. The torque needed to maintain the needle in this position will be.....$J$