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A coil having 100 turns, area of 5 × 10⁻³ m², carrying current of 1 mA is placed in uniform magnetic field of 0.20 T such a way that plane of coil is perpendicular to the magnetic field. The work done in turning the coil through 90° is ______ μJ.

Asked in JEE Main 6th April 2nd Shift 2024 · Torque and potential energy

Answer: 100

Step-by-step solution

Plane perpendicular to B⃗ means M⃗ is along B⃗ (θ = 0°).

M = NIA = 100 × 10⁻³ × 5 × 10⁻³ = 5 × 10⁻⁴ A m²

W = MB(cos 0° - cos 90°) = 5 × 10⁻⁴ × 0.2 = 10⁻⁴ J = 100 μJ

→ 100

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