Q. A rectangular coil $20\ cm \times 20\ cm$ has 100 turns and carries a current of $1\ A$. It is placed in a uniform magnetic field $B = 0.5\ T$ with the direction of magnetic field parallel to the plane of the coil. The magnitude of the torque required to hold this coil in this position is
A) Zero
B) 200 $N$-$m$
C) 2 $N$-$m$
D) 10 $N$-$m$
Explanation
(c) $\tau = NBiA = 100 \times 0.5 \times 1 \times 400 \times 10^{- 4} = 2\ N - m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.