Question

In which process, there is no change in the internal energy of the system?
A.Isothermal
B.Adiabatic
C.Free expansion
D.Cyclic

Answer 1

Hint: Firstly in the question we need to get the explanation of what is internal energy of a thermodynamic system. In the explanation we get that the internal energy for a whole system is a function of the temperature. Now we can observe that in whatever process the temperature remains constant the internal energy wouldn’t change and vice versa. By comparing we will get the answer.

Complete step by step answer:
To find the internal energy in the field of thermodynamics, we need to know that the internal energy of a system is the energy contained within the system. This energy excludes the kinetic energy of motion of the system when worked as a whole. So we can say that the potential energy of the system when calculated as a whole is also due to the external force fields.
This also keeps the detailed account of the imminent gains and losses of the energy of the system that are due to changes in its internal state.
Now we have to get the cases separately for each of them
1.Isothermal process : In this there is no change in the internal energy as the temperature remains constant and the internal energy is a function of temperature.
2.Adiabatic process : In this there is change in the internal energy as the temperature does not remain constant and the internal energy is a function of temperature.
3.Free expansion : In this there is no change in the internal energy as the temperature remains constant and the internal energy is a function of temperature.
4.Cyclic process : In this there is no change in the internal energy as the temperature remains constant and the internal energy is a function of temperature

So, the correct answer is “Option A,C,D .

Note:
For each of the processes in thermodynamics namely Isothermal, Adiabatic, Free expansion and Cyclic. There is always any one of the physical quantities that will change specifically whereas the others will be compared accordingly. For eg. The changing temperature will give the change in other quantities like pressure or volume.