Q 12-05-082JEE MainJEE Main 2025 (3 Apr, Shift 2)Easy
A magnetic dipole experiences a torque of $80\sqrt3\ \text{N m}$ when placed in a uniform magnetic field in such a way that the dipole moment makes an angle of $60^\circ$ with the magnetic field. The potential energy of the dipole is:
Answer: (D) $-80\ \text{J}$
$$\tau = MB\sin60^\circ = \frac{\sqrt3}{2}MB = 80\sqrt3 \Rightarrow MB = 160\ \text{J}$$
$$U = -MB\cos60^\circ = -160\times\frac12 = -80\ \text{J}$$
Solution by Sreeraj P, M.Sc Physics