Current `i` is carried in a wire of length `L`. If the wire is turned into a circular coil, the maximum magnitude of torque in a given magnetic field `B` will be

Options

A. `(LIB^(2))/(2)`
B. `(LI^(2)B)/(2)`
C. `(L^(2)IB)/(2)`
D. `(L^(2)IB)/(4 pi)`

Answer

D

Explanation

`tau_(max) = NABI " "= 1 xx 1 xx (pi r^(2))B`
`[(2pi r = L),(r = (L)/(2pi))]`
`tau_(max) = pi I((L)/(2pi))^(2) B " "rArr" "tau_(max) = (L^(2) IB)/(4 pi)`