Which of the following is represented by the area enclosed by a hysteresis loop (B-H curve)?
$\left( A \right)$ Permeability
$\left( B \right)$ Retentivity
$\left( C \right)$ Heat energy lost per unit volume in the sample
$\left( D \right)$ Susceptibility

Hint: In this question use the concept that any magnetic material has some hysteresis loop except air core this hysteresis loop represents the loss in the magnetic system while transferring the power from one terminal to another terminal using magnetic core for example transformer.

Complete step-by-step solution -


As we know while transferring power from the source end to the receiving end, both power cannot be equal practically as there is some power loss in the core of the material which is called as core loss.
These core loss are of two types:
$\left( i \right)$ Eddy current loss
$\left( {ii} \right)$ Hysteresis loss.
Eddy current loss is due to eddy currents flowing in the magnetic material such as the core of the transformer which is made up of soft magnetic material. We can reduce these eddy current losses using thin laminations of the core of the transformer.
And every magnetic material has some hysteresis losses and every magnetic material has some B-H curve the area of this curve is called as hysteresis loss as shown in the figure, we reduce this hysteresis loss but cannot completely eliminate as air core is not possible, so these curve represents the energy lost per unit volume (i.e. volume of the core)
So this is the required answer.
Hence option (C) is the correct answer.

Note – Whenever we face such types of questions always remember that every magnetic material has some hysteresis loop which is the loss of energy while transferring the power form the source end to the receiving we can reduce this loss but cannot completely eliminated using different cores such as soft ferromagnetic material has lower hysteresis loop and hard magnetic material has larger hysteresis loop.