Question

A circular coil of $10$ turns and radius $10 \,cm$ is placed in a uniform magnetic field of $0.1 \,T$ normal to the plane of the coil. If the current in the coil is $5 \,A$ then the magnitude of the torque on the coil is

• A. $500 \pi \,N m$
• B. $0.05 \pi \,N m$
• C. $0.005 \pi \,N m$
• D. zero

Answer 1

Answer: (D)

Magnitude of torque on the coil is given as
$\tau=|m \times B| $
$\Rightarrow \tau=N I A B \sin \theta$
where, $\theta$ is the angle between axis of loop (normal to the loop) and direction of magnetic field.
Here, $\theta=0 $
So, $ \tau=0$