Physics - Magnetism Question with Solution | TestHub

For the unstable equilibrium, the angle between the magnetic moment and magnetic field is 180^o. ($\because$In this position it will be in a direction to magnetic field thus no torque will act on it.)

$\theta =180^{\text{o}}$

The potential energy of the magnet

$\mathrm{U}=-\mathrm{mB} \cos {180}^{°}$

$=- 0.32\times 0.15 (- 1) = 4.8\times {10}^{-2} \mathrm{J}$

Thus, for the unstable equilibrium, the potential energy is$4.8\times {10}^{-2} \mathrm{J}$.