Question

A magnetic dipole in a constant magnetic field has :

• 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 1

Answer: (C)

zero potential energy when the torque is maximum.

Answer 2

PE = - PE cos $\theta$
$\tau$ = PE sin $\theta$
$\tau_{max}$ when $\theta = 90^{\circ}$
PE $= 0$