Question

A circular coil of 100 turns and effective diameter 20 cm carries a current of 0.5 A. It is to be turned in a magnetic field of B = 2.0T from a position in which the normal to the plane of the coil makes an angle equals to zero to one in which equals to ${180}^{\circ }$ . The work required in this process is:

• A. $\pi J$
• B. $2\pi J$
• C. $4\pi J$
• D. $8\pi J$

Answer 1

Answer: (B)

$2\pi J$

We have the equation,

Work required, $W=MB(1-Cos\theta )$

Also,

$M=NIA$

Then,

$W=NIAB(1-Cos\theta )$

$W=(2\times 100\times 0.5\times 3.14\times (1-Cos{180}^0\left)\right)$

$=6.28J=2\pi J$