In a uniform magnetic field of strength 0 . 15 T , a short bar magnet of magnetic moment m = 0 . 32 J T - 1 is placed. The potential energy of the magnet in its unstable equilibrium position is

Step-by-step solution

For the unstable equilibrium, the angle between the magnetic moment and magnetic field is 180 o . ( ∵ In this position it will be in a direction perpendicular to magnetic field thus maximum torque will act on it.) θ = 1 8 0 o Potential energy of the magnet U = - mB cos 180 o = - 0.32 x 0.15 (- 1) = 4.8 x 10 -2 J Thus, for the unstable equilibrium the potential energy is 4.8 x 10 -2 J.