Question

Assertion : If a compass needle be kept at magnetic north pole of the earth, the compass needle may stay in any direction.
Reason : Dip needle will stay vertical at the north pole of earth

• A. If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion
• B. If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion
• C. If the Assertion is correct but Reason is incorrect
• D. If both the Assertion and Reason are incorrect
• E. If the Assertion is incorrect but the Reason is correct

Answer 1

Answer: (B)

The earth has only vertical component of its magnetic field at the magnetic poles. Since compass needle is only free to rotate in horizontal plane where H = 0, hence the compass needle may stay in any direction. The dip needle rotates in a vertical plane and angle of dip at poles is $90^{\circ }$. So it will stand vertical.