Question

The Earth’s magnetic field:
(A) Varies in magnitude but not direction
(B) Varies in direction but not magnitude
(C) Varies in both magnitude and direction
(D) Is centered exactly about the center of the earth

Answer 1

Hint The magnetic field of the earth is not constant but changes irregularly from place to place on the surface of the earth and even at a given place it varies with time too. The field strength is determined by the magnetic field lines passing through that place which are different at different positions. So, it varies in both direction and magnitude.

Complete step-by-step solution

The earth is rotating about its axis which passes through the Atlantic and Antarctica. Due to the nature of earth’s magnetism, these poles were later called the North and South pole. They were named as such because the earth’s magnetic field lines appear to be originating from the North Pole and converge into the south pole. The direction of the magnetic field is shown in this diagram above. The compass works by utilizing this feature of the earth, i.e. its magnetic field. It has a magnet situated in it, which is free to rotate in the XY plane. This magnet will align itself with the earth’s magnetic field and always point towards the north. Also, magnetic field strength is given by the number of magnetic files passing through an area. As you can see, the field strength is maximum at the poles and the minimum at the equator.

Therefore, the correct answer is option C

Note: You should notice that the axis of rotation of earth does not coincide with the magnetic field lines, so the supposed magnet inside the earth is titled.