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 moment of work done in rotating it through ${180}^{\circ }$ from its equilibrium position will be

• A. 0.1 J
• B. 0.2 J
• C. 0.4 J
• D. 0.8 J

Answer 1

The correct option is A 0.1 J

Magnetic moment of current carrying loop $=M=iAN=i\left(\pi r^2\right)N$

$W=MB\left(\cos {\theta }_1-\cos {\theta }_2\right)=MB\left(\cos 0^0-\cos {180}^0\right)=2MB$

$=0.1J$

$\therefore$ Option $A$ is correct.