A coil in the shape of an equilateral triangle of side l is suspended between the pole pieces of a 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 triangle is ............................
Options:
(a) `2/sqrt3(tau/(BI))^(1/2)`
(b) `2/3(tau/(BI))`
(c) `2(tau/(sqrt3BI))^(1/2)`
(d) `1/sqrt3tau/(BI)`