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 acts on it, the side l of the triangle is
- 2 3 ( Bi )
- 2 ( 3Bi )1/2
- 2 3 ( Bi )1/2
- 1 3 Bi
Answer
(2) 2 ( 3Bi )1/2
Solution
B lies in the plane of the coil, so m B and = iAB
Area of the equilateral triangle A = 34l2
= 34l2 iB
l2 = 4 3Bi
l = 2 ( 3Bi )1/2
Answer: (2)