Question

A refrigerator works on the principle of ______________ law of thermodynamics.
(a)- Zeroth
(b)- First
(c)- Second
(d)- Third

Answer 1

The law of thermodynamic says that the energy is transferred from a higher temperature to a lower temperature. But the energy has to be transferred from lower temperature to the higher temperature external work has to be applied.

Complete step by step answer:
According to the second law of thermodynamics: "It is impossible for a self-acting machine unless energy is provided by any external agency, to transfer heat from a body having lower temperature to another at a higher temperature". This is the basic principle used for the working of a refrigerator.

Let us understand the working of a refrigerator. Suppose in a refrigerator, the working substance absorbs a ${{Q}_{2}}$amount of heat from the cold reservoir at temperature${{T}_{2}}$. And a W amount of work is done on it by some external agency (a compressor pump driven by an electric motor) and rejects a larger amount of heat ${{Q}_{1}}$to the source at temperature${{T}_{1}}$. The diagram of working of the refrigerator is given below:

In the refrigerator used in our house, food and ice are the cold reservoir and the surrounding act as a hot reservoir. The work is done by electric motor and freons ($CC{{l}_{2}}{{F}_{2}}$)
So, this functioning is explained by the second law of thermodynamics.

So, the correct answer is an option (c)- Second.

Note: We can find the coefficient of performance of the refrigerator and it is the ratio of the amount of heat removed to the mechanical work done by the motor on the refrigerator. The formula is: $\beta =\frac{{{Q}_{2}}}{W}$ .