A magnetic needle lying parallel to the magnetic field requires W units of work to turn it through an angle 45^ . The torque required to maintain the needle in this position will be

Step-by-step solution

Work done by magnet to turn from angle array l array l ₁ to ₂ ~W = MB ( ₁- ₂ ) = MB ( 0^ - 45^ ) array = MB (1- 1 2 )= ( 2 -1 2 ) MB array Also torque acting on the magnet array l = MB 45^ = MB 2 ~W =( 2 -1) = W ( 2 -1) array