A coil in the shape of an equilateral triangle of side `l` is suspended between the pole pieces of permanent magnet. Such that `vecB` is in plane of the coil. If due to a current I in the triangle, a torque `tau` acts on it, the side l of the triangel is:

Options

A. `2/sqrt3((tau)/(BI))`
B. `2((tau)/(sqrt3BI))^(1//2)`
C. `2/sqrt3((tau)/(BI))^(1//2)`
D. `1/sqrt3((tau)/(BI))`

Explanation

`IAB sin 90^@=IAB`
[Angle between A and B is `90^@`]

Area `A=1/2xxbasexxheight`
`=1/2xxlxxlsin60^@=sqrt3/4l^2`
`tau=I(sqrt3/4l^2)B` so `l^2=(4tau)/(sqrt3BI)`
So `l=2((tau)/(sqrt3BI))^(1//2)`