Question

A current-carrying rectangular coil placed in a uniform magnetic field. In which orientation will the coil rotate?

• A. In any orientation
• B. The magnetic field is parallel to the plane of the coil
• C. The magnetic field is at 45° with the plane of the coil
• D. The magnetic field is perpendicular to the plane

Hint:

The torque on a current-carrying coil in a magnetic field is greatest when the field is perpendicular to the plane of the coil.

Answer 1

The Correct Option is D

Step 1: Understanding the Torque on a Current-Carrying Coil
When a current-carrying coil is placed in a uniform magnetic field, the magnetic force on the coil produces a torque that tends to rotate the coil.
The magnitude of the torque is greatest when the magnetic field is perpendicular to the plane of the coil. 
Step 2: Why Other Options are Incorrect 
Option (a) is incorrect because the coil will not rotate in just any orientation.
The torque produced depends on the angle between the magnetic field and the coil's plane.
Option (b) is incorrect because if the magnetic field is parallel to the plane of the coil, no torque will be produced.
Option (c) is incorrect because while a 45° angle will produce some torque, it is not the maximum torque. 
Step 3: Conclusion 
The coil will rotate most effectively when the magnetic field is perpendicular to its plane, maximizing the torque.