A coil in the shape of an equilateral triangle of side `0.01` m is suspended from the vertex such that is hanging in a vertical plane between pole pieces of a permanent magnet producing a horizontal magnetic field of (`4×10^(-2)`T).If a current of 1A is passing through it and the magnetic field is parallel to its field,then the torque acting on the coil is

Options

A. `5 sqrt3 xx 10^(-7) N-m`
B. `5 sqrt3 xx 10^(-1) N-m`
C. `(sqrt3)/(5) xx 10^(-7) N-m`
D. None of these

Answer

A

Explanation

`tau= I A B sin theta`
`A= (1)/(2) xx b xx l`
`= (1)/(2) a xx (a sqrt3)/(2)= (sqrt3)/(4) a^(2)= sqrt3 xx 10^(-4) m^(2), theta= 90^(@)`
`tau = 0.1 xx sqrt3 xx 10^(-4) xx 5 xx 10^(-2) = 5 sqrt3 xx 10^(-7) N-m`