Question

A short bar magnet placed with its axis at `30^(@)` with a uniform external magnetic field of 0.25 T experiences a torque of magnitude equal to `4.5 xx 10^(-2)J`. What is the magnitude of magnetic moment of the magnet ?

Answer 1

Here `theta = 30^(@), B 0.25 T, r = 4.5 xx 10^(-2) J, M = ?`
As `r = mB = sin theta :. m = (r)/(B sin theta) = (4.5 xx 10^(-2))/(0.25 sin 30^(@))`