Q. A rectangular coil of length 0.12m and width 0.1m having 50 turns of wire is suspended vertically in a uniform magnetic field of strength 0.2 Weber/$m^2$. The coil carries a current of 2 A. If the plane of the coil is inclined at an angle of 30° with the direction of the field, the torque required to keep the coil in stable equilibrium will be :
A) 0.12 Nm
B) 0.15 Nm
C) 0.20 Nm
D) 0.24 Nm
Explanation
[Solution] The normal makes 60° with B: $\tau = NIAB\sin 60° = 50 \times 2 \times 0.012 \times 0.2 \times 0.866 \approx 0.20$ Nm. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.