BITSAT2017PhysicsMagnetic Effects of CurrentActual
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
Options
- A2 τ 3 B i 1 2
- B2 3 τ B i
- C2 τ B i 1 2
- D1 3 τ B i
Correct answer
A. 2 τ 3 B i 1 2
Step-by-step solution
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