JEE Main · 2025 · 03 Apr 2025 · Shift 2 · Magnetic Effects of Current

A magnetic dipole experiences a torque of

803 Nm

when placed in uniform magnetic field in such a way that dipole moment makes angle of

6 0^{\circ}

with magnetic field. The potential energy of the dipole is :

(A)80 J
(B) $- 403 J$
(C)-60 J
(D)-80 J✓ Correct

Answer: (D)

Solution

The torque on a dipole is

τ = M B sin θ

. With

θ = 6 0^{\circ}

803 = M B \cdot \frac{3}{2}

, giving

M B = 160 J

. The potential energy is

U = - M B cos θ = - 160 \times cos 6 0^{\circ} = - 160 \times \frac{1}{2}

, so the potential energy of the dipole is

- 80 J

JEE Main · 2025 · 03 Apr 2025 · Shift 2 · Single correct option

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