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A closely wound solenoid of 2000 turns and area of cross-section 1.5 × 10–4 m² carries a current of 2.0 A. It suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field 5 × 10–2 tesla making an angle of 30° with the axis of the solenoid. The torque on the solenoid will be:
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- 3 × 10–2 N-m
- 3 × 10–3 N-m
- 1.5 × 10–3 N-m
- 1.5 × 10–2 N-m
Correct Option: D
Torque on the solenoid is given by τ = MB sin θ
where θ is the angle between the magnetic field and the axis of solenoid.
M = niA
∴ τ = niA B sin 30°
= 2000 × 2 × 1.5 × 10-4 × 5 × 10-2 × 1/2
= 1.5 × 10-2 N - m
