Question

A compass works with the help of ______________.
A) Solar energy
B) Moon’s gravity
C) Earth’s magnetic field
D) Earth’s gravity

Answer 1

Hint: The working of the compass is rooted in the concept of magnetism. It is based on the observation that a bar magnet, when suspended freely in the air with the help of a thread or string, would align itself along the geographical north-south direction.

Complete step by step answer:
Step 1: Describing the working principle of the compass will determine the correct option.
The Earth is considered to be a giant bar magnet as its inner iron core and the outer liquid core rotate and spin, due to the rotation and spinning of the Earth, to generate a magnetic field around the Earth. Every magnet will have a north pole and a south pole and the Earth’s magnet thus also has a north pole and a south pole.
The compass needle consists of a needle which is placed on a pivot or pin so that it can move freely. The compass needle, being a magnet, will interact with the bar magnet inside the Earth. The basic principle of magnetism is that like poles repel while unlike poles attract. So when the compass needle points north it is, in fact, being attracted to the geographic north of the Earth which is actually the south pole of the magnet inside the Earth.
This is sown in the figure below:

Thus the compass needle will orient along the geographical north-south direction of the Earth.

Thus the correct option is C.

Note:
The magnetic north pole and south pole of the Earth do not exactly coincide with the geographic north and south of the Earth. The magnetic north pole and the south pole are found to be continuously changing over time. Scientists have determined that the magnetic north pole and south pole constantly shift in every thousand years. But the working of the compass needle is not significantly affected by this shift in the poles.