A magnetic dipole in a constant magnetic field has

Options

A. maximum potential energy when the torque is maximum.
B. zero potential energy when the torque is minimum
C. zero potential energy when the torque is maximum.
D. minimum potential energy when the torque is maximum.

Answer

C

Explanation

Potential energy is given by : `U = - MB cos theta`
Torque is given by : `tau = MB sin theta `
We can see that Potential energy is minimum and maximum when torque is zero, hence options (a) and (d) are not correct.
Potential energy is zero when ` theta = pi//2`, hence when torque is maximum. So option (b) is not correct but option (c) is correct.