A current-carrying loop is placed in a uniform magnetic field such that its plane is perpendicular to the field. What is the torque acting on the loop?
Correct: A
Torque is maximum when the loop is parallel to the field and zero when perpendicular. Since the loop's plane is perpendicular, the angle between $\vec{mu}$ and $\vec{B}$ is 0° ($ au = mu B sin heta $), resulting in zero torque.