Q. A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It:
A) will stay in east-west direction only
B) will become rigid showing no movement
C) will stay in any position
D) will stay in north-south direction only
Explanation
[Solution from source] At a geomagnetic pole the earth's field is vertical, so its horizontal component is zero. A needle free to move only in a horizontal plane experiences no directing torque and stays in any position it is placed. It does not lock into north-south because there is no horizontal field to align it. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.