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

Question

Read the assertion and reason carefully to mark the correct option out of the options given below. 

(A) If both assertion and reason are true and the reason is the correct explanation of the assertion. 

(B) If both assertion and reason are true but reason is not the correct explanation of the assertion, 

(C) If assertion is true but reason is false. 

(D) If the assertion and reason both the false. 

(E) If assertion is false but reason is true. 

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.

Answer 1

The correct option (B) If both assertion and reason are true but reason is not the correct explanation of the assertion,

Explanation:

We know at magnetic poles, the horizontal component of earth’s field is zero only vertical component exists. So, as compass needle is free to rotate in horizontal plane, thus affected by horizontal component only. As H = 0, hence needle may stay in any direction. 

The dip needle rotate in vertical plane & angle of dip at the poles is 90°. Hence dip needle will stand vertical at north pole of earth. Hence both statements are true but reason is not correct explanation of assertion.