A bar magnet having a magnetic moment of 2 x 104 JT-1 is free to rotate in a horizontal plane. A horizontal magnetic field B=6 x 10-4 T exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction 60o from the field is

The work done in rotating a magnetic dipole against the torque acting on it, when placed in magnetic field is stored inside it in the form of potential energy. When magnetic dipole is rotated from initial position θ=θ1 to final position θ=θ2, then work done = MB (cos θ1- cos θ2) =MB1-12=2 x 104 x 6 x 10-42=6 J