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. `(sqrt3BI)/(4L^(2))`
B. `(sqrt3BIL^(2))/4`
C. `(4L^(2))/(sqrt3BI)`
D. `(sqrt3L^(2))/(4BI)`

Answer

B

Explanation

`h=Lsin60◦=(Lsqrt3)/2 therefore` Area of the triangle`=1/2 xx (L xx Lsqrt3)/2=(3L^(2))/4 therefore` Torque `(tau)=BIA=(3BL^(2)I)/4`