Question

A magnet can be completely demagnetized by which one of the following processes?
A) Breaking the magnet into small pieces
B) Heating it slightly
C) Applying a reverse field of appropriate strength
D) Dropping it into ice-cold water

Answer 1

The molecules in the magnet are aligned to one direction due to which breaking does not affect direction or heating. Also, ice water has no property to change the dipole of magnetism.

Complete Step by Step Answer:
We are going to check each option one by one and then find the solution for the magnetism.
Let’s check option (A):
Breaking the magnet into small pieces:
When we break a magnet into two, both act as magnets that both have a north and south pole each. In both these pieces, the corresponding north and south poles remain on the sides as in the original magnet. This means that the 2 broken sides must get oppositely polarized.
Thus from the above statement, we can say that breaking will not be able to demagnetize.

Let’s check for option (B):
Heating it slightly
At around 80 °C, a magnet will lose its magnetism and it will become demagnetized permanently if exposed to this temperature for a period, or if heated above their Curie temperature. Heat the magnet even more, and it will melt, and eventually vaporize.
Thus from the above statement, we can say that heating will not be able to be demagnetized.

Let’s check for (C):
Applying a reverse field of appropriate strength
We like to represent this force effect of a magnet on iron-like objects with a concept. The strength is represented by the density of the magnetic field lines motion of electrons (moving electric charge) is the fundamental reason for magnetism. In general, alignment within a domain is the same for all atoms of that domain.
And hence by applying a reverse field of appropriate strength it will cancel out the magnetic field in a particular direction with the opposite direction and demagnetize it.

Let’s check for option (D):
Dropping it into ice-cold water
Magnets are made up of atoms. In extremely cold temperatures the atoms will move more slowly and less randomly. This creates a more controlled alignment of the atoms that produce the magnetic field and a slightly stronger magnetism.
Thus from the above statement, we can say that cold water will not be able to demagnetize.

$\therefore$ Option (C) is the correct answer.

Note:
The irons which have a property of getting demagnetized are mostly used so that they can be reused again in the working station. Soft iron is an example and it is also demagnetized by applying the reverse field of appropriate strength.