Torque on a Magnetic Dipole (bar magnet) in a Uniform Magnetic Field

Torque on a Magnetic Dipole (bar magnet) in a Uniform Magnetic Field:

Let a bar magnet is placed in a uniform magnetic field B. The length of the bar magnet is 2l and strength of each pole m.

The magnet is held at angle theta with the direction of B.

These equal and opposite forces from a couple which tends to rotate the magnet clockwise.

 Torque acting on the bar magnet-