Problem

A coil of a moving coil galvanometer twists through

90^\circ

when a current of one microampere is passed through it. If the area of the coil is

10^{-4} \text{ m}^2

and it has 100 turns, calculate the magnetic field of the magnet of the galvanometer. Given,

k = 10^{-8} \text{ N-m/degree}