A coil in the shape of an equilateral triangle of side l is suspended between the pole pieces of a permanent magnet such that B is in plane of the coil. If due to a current i in the triangle, a torque τ rests on it, the side l of the triangle is

Question

A coil in the shape of an equilateral triangle of side l is suspended between the pole pieces of a permanent magnet such that B is in plane of the coil. If due to a current i in the triangle, a torque τ rests on it, the side l of the triangle is, 2 τ 3 B i 1 2, 2 3 τ B i, 2 τ B i 1 2, 1 3 τ B i

MARKS App · Accepted Answer

Torque acting on equilateral triangle in a magnetic field B is τ = i A B sin θ Area of triangle LMN , A = 3 2 l 2 and θ = 90 ° Substituting the given values in expression for torque, we get τ = i × 3 4 l 2 B sin 90 ° τ = 3 4 i l 2 B ∵ sin 90 ° = 1 l 2 = 4 τ 3 B i Here, l = 2 τ 3 B i 1 2

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