Question

A circular coil of magnetic moment 20 A-m² is placed in a uniform magnetic field of 2 T.
The amount of workdone in rotating it through 180° from its equilibrium position will be

Answer 1

Answer:

check attachment for solution

Answer 2

Answer:

The amount of work done on rotating the coil through 180° is equal to 80J.

Explanation:

Given:

Magnetic moment of circular coil, $M=20Am^{-2}$

Applied uniform magnetic field, $B=2T$

The angle of rotation $\theta_{2}=180^{o}$ and $\theta_{1}=0^{o}$

Now, Work done, $W=MB[cos\theta_{1}-cos\theta_{2}]$                        ...............(1)

Put the values of $M$, $B$ , $\theta_{1}$ $and$ $\theta_{2}$ in eq.(1),

$W=(20Am^{2})(2T)[cos0^{o}-cos180^{o}]$

$W=40(\frac{J}{T})(T)[1-(-1)]$                                  $[Am^{2}=JT^{-1}]$

$W=40(1+1)J$

$W=80J$

The work done by coil on rotation is equal to 80J.