Question

A bar magnet has no markings to indicate its poles. How would you find out near which end its north pole is located?

Answer 1

Bar Magnet

1. A bar magnet is a rectangular piece of metal that is made up of ferromagnetic substances like iron.
2. In ferromagnetic materials, each atom or molecule possesses permanent atomic dipoles which interact strongly with each and may cause spontaneous magnetization within a single domain even in the absence of an external field.
3. They are strongly attracted by magnetic fields.
4. A small external field can cause large magnetization.
5. In a ferromagnetic material, a large group of neighboring dipoles get aligned parallel to each other even in the absence of an external magnetizing field.
6. This group of paralleled oriented atomic dipoles is called a domain.
7. Thus, a ferromagnetic sample may be assumed to consist of a large number of domains that can align themselves towards the magnetic field in the presence of an external magnetic field.
8. Therefore, bar magnets are known to be permanent magnets which has two magnetic poles, a north pole, and a south pole.

Poles of a Magnet

1. We know that earth itself is a huge magnet due to the presence of the huge iron core at its centre.
2. Therefore the magnet with unknown poles must be suspended freely with a massless string.
3. The freely suspended magnet will always align itself in the north-south direction according to earth.
4. Hence the face of the magnet which is facing the north pole of the earth will represent the north pole of the magnet.
5. Similarly, the face of the magnet which is facing the south pole of the earth will represent the south pole of the magnet.