5.3 A short bar magnet placed with its axis at 30° with a uniform external magnetic field of 0.25 T experiences a torque of magnitude equal to 4.5 × 10–2 J. What is the magnitude of the magnetic moment of the magnet?

Magnetic field strength, B=0.25T
Torque on the bar magnet, 
Angle between the bar magnet and the external magnetic fieldθ=30°
Torque is related to the magnetic moment (M) as: T=MB sinθ
Hence, the magnetic moment of the magnet is 0.36 J T-1.