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

Question

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, 4 . 8 × 10 - 2 J, 9 . 6 × 10 - 2 J, 2 . 8 × 10 - 2 J, 1 . 2 × 10 - 2 J

MARKS App · Accepted Answer

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.

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