Question

In the following figures (a) to (d), variation of volume with change of pressure along the path ABCDA is shown. Change in internal energy of the gas will be -

• A. positive in all cases from (a) to (d)
• B. positive in cases (a), (b) and (c), but zero in case (d)
• C. negative in cases (a), (b) and (c), but zero in case (d)
• D. zero in all the four cases

Answer 1

The correct option is D zero in all the four cases

Internal energy is a state function.
That is, it depends only on the initial and final states of the gas.
In a cyclic process, initial state coincides with final state.
So, change in internal energy $\Delta U=0$ in all four cases.