Question

A circular coil of radius 4 cm has 50 turns. In this coil a current of 2 A is flowing. It is placed in a magnetic field of $0.1weber/m^2$. The amount of work done in rotating it through ${180}^{\circ }$ from its equilibrium position will be

• A. 0.1 J
• B. 0.2 J
• C. 0.5 J
• D. 0.8 J

Answer 1

The correct option is C 0.5 J

Work done in rotating a coil through an angle $\theta$ from its equilibrium position is $W=MB(1-cos\theta )$ where $\theta ={180}^{\circ }$ and $M=50\times 2\times \pi (4\times {10}^{-2}{)}^2=50.24\times {10}^{-2}A-m^2$. Hence W = 0.5 J