A moving coil galvanometer has 100 turns and each turn has an area `2.0 cm^2`. The magnetic field produced by the magnet is `0.01 T`. The deflection in the coil is `0.05` radian when a current of `10 mA` is passed through it. Find the torsional constant of the suspension wire.

Explanation

We have
`I = K/(nAB) theta`
or, ` K = (inAB)/(theta)`
`= ((10 xx 10^(-3) A) xx 100 xx (2.0 xx 10^(-4) m^2) xx 0.01 T)/(0.05 rad)`
`= 4.0 xx 10^(-5) N m rad^(-1)`.