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Question
A rectangular coil of 100 turns has length 5 cm and width 4 cm. It is placed with its plane parallel to a uniform magnetic field and a current of 2 A is sent through the coil. Find the magnitude of the magnetic field B if the torque acting on the coil is 0.2 N m−1
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Solution
Given:
No. of turns in the coil, n = 100
Area of the coil, A = 5 × 4 cm2 = 20 × 10−4 m2
Magnitude of current = 2 A
Torque acting on the coil, τ = 0.2 N m−1
τ = niA × B
⇒τ = niBA sin 90°
⇒ 0.2 = 100 × 2 ×20 × 10−4 × B
⇒ B = 0.5 T
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