AIIMS 2019 Physics Earth's Magnetic Field MCQ 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.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Correct Answer
Detailed Explanation
At the magnetic poles of Earth, the magnetic field lines are directed vertically downward, resulting in a vertical component (V) of the magnetic field and a horizontal component (H) of zero. While it is true that a compass needle aligns with the horizontal component of the magnetic field, at the poles where H = 0, the compass needle does not have a horizontal force to balance against, causing it to point vertically rather than horizontally. Therefore, the statement that the dip needle will stand vertical at the North Pole is incorrect, as it does not account for the fact that the compass needle's behavior is influenced by the vertical component rather than simply being free to rotate in the horizontal plane. Options (A) and (C) are incorrect because they either affirm the misleading statement or suggest uncertainty where the physics is clear.
Found an issue with this question?