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. `(L^(2)B^(2))/(2)`
B. `(L^(2)B)/(2)`
C. `(L^(2)iB)/(4pi)`
D. `(L^(2)B)/(4pi)`

Answer

C

Explanation

Torque `tau_("max")=NiAB=1xxixx pir^(2)xxB ( :. 2pir=L rArr r=(L)/(2pi))`
`tau_("max")pi i((L)/(2pi))^(2) B=(L^(2)I B)/(4pi)`