Question

A circular coil of 25 turns and radius 12 cm is placed in a uniform magnetic field of 0.5 T normal to the plane of the coil. If the current in the coil is 6 A then total torque acting on the coil is

• A. zero
• B. 3.4 N m
• C. 3.8 N m
• D. 4.4 N m

Answer 1

The correct option is A zero

The torque acting on the coil $\tau$=|$\overline{m}$ X $\overline{B}$ | =$mB\sin \Theta$
Here the circular coil is placed normal to the direction of magnetic field then the angle between the. direction of magnetic moment ($\overline{m}$) and magnetic field ($\overline{B}$) is zero, then
$\tau$ = $mBsin\Theta$ = $mBsin0$ = 0 $\tau =0$