Question

A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It.

• A. will become rigid showing no movement
• B. will stay in any position
• C. will stay in north-south direction only
• D. will stay in east-west direction only

Answer 1

The Correct Option is B

A compass needle aligns itself with the horizontal component of the Earth's magnetic field. The Earth's magnetic field has both horizontal and vertical components, which vary based on the position on the Earth's surface.

At the geomagnetic poles, the vertical component of the magnetic field is dominant, and the horizontal component is nearly zero. Therefore, a compass needle that is free to move only in the horizontal plane would have no substantial magnetic force to orient itself in any specific direction. Hence, at the geomagnetic poles, the compass needle can point in any direction and will not have a preferred alignment.

Now, let's analyze the options:

• Will become rigid showing no movement: This option is incorrect because the lack of a significant horizontal component does not make the needle rigid. It simply means there is no force to direct its movement.
• Will stay in any position: This option is correct. The absence of a dominant horizontal component means the needle lacks directional preference.
• Will stay in north-south direction only: Incorrect, as previously mentioned, there is not enough horizontal component to direct it in the north-south direction.
• Will stay in east-west direction only: Similarly, this is incorrect because there is no horizontal guidance to maintain the needle in the east-west direction.

Therefore, the correct answer is that the compass needle, when taken to a geomagnetic pole, will stay in any position.