A current loop of magnetic moment 0.5 A m$^2$ sits in a 0.4 T field with its moment perpendicular to the field. Set the magnitude of the torque on it, in N m.

0.2 (answers within ±0.03 count)

$\tau = mB\sin\theta = 0.5 \times 0.4 \times 1 = 0.2$ N m. The net force is zero in a uniform field, opposite sides cancel, so the loop turns without being dragged. A net force needs a field gradient.