Question

A piece of material moves very slowly towards a pole of magnet. The material must be _______.
A. Diamagnetic
B. Ferromagnetic
C. Paramagnetic
D. Ferrimagnetic

Answer 1

We are dealing with some material that is moving slowly in the vicinity of a pole of a magnet. When a material moves slowly in the presence of an external magnetic field, its susceptibility should definitely be negative. So, find the material among the given ones that has negative susceptibility.

Complete step by step solution:
In the question, we are given a piece of material that moves very slowly towards a pole of magnet. We are supposed to identify this material from the given options.
In order to answer this question, we have to be aware of the properties of the materials given in the options and hence determine the apt answer.
For defining the given terms, we will have to introduce a quantity that is susceptibility. Susceptibility$\left( \chi \right)$ can be defined as the measure of as to how a magnetic material is seen to respond to an external magnetic field.
Now the value of this quantity for the above materials goes like this. It is known to be negative for a dia-magnetic materials, it is small and positive for paramagnetic ones and is large and positive for ferromagnetic materials.
Negative value of susceptibility for diamagnetic materials confirms the fact that they are very weakly attracted to external magnetic fields. This happens as a result of the dipole moments of the spin of the electrons being zero.
Therefore, the given particle would be diamagnetic as the others are all reactive to external magnetic fields and will show faster movement in the vicinity of magnets.
Hence, option A is the correct answer.

Note: The ferromagnetic materials he large net magnetization even for very small external magnetic fields. Susceptibility is positive for this category of materials too. They are also known to behave as paramagnetic and ferromagnetic materials above and below curie's temperature respectively.