Find the maximum torque of a loop with magnetic moment $12.5$ and flux density $4$ units.

Two points $A$ and $B$ are situated perpendicular to the axis of $4 \mathrm{cm}$ long bar magnet at distances $\mathrm{x}$ and $3\mathrm{x}$ from its centre on opposite sides. The ratio of magnetic inductions at $A$ and $B$ will be equal to

Torque acting on a coil is $2\times {10}^{-5} \mathrm{N} \mathrm{m}$. If the torque produces angular deflection of $10°$ in the coil, then the torsional rigidity of the suspension fibre (in $\mathrm{N} \mathrm{m}$/$\mathrm{degree}$) connected to coil is