In following figs. Variation of volume by change of pressure is shown in Fig. A gas is taken along the path `ABCDA`. The change in internal energy of the gas will be:

Options

A. positive in all cases from `(1) to (4)`
B. Positive in cases `(1), (2) and (3)` but zero in case `(4)`
C. Negative in case `(1), (2) and (3)` but zero in case `(4)`
D. zero in all the four cases

Answer

D

Explanation

In each cyclic process
`DeltaU =U_("final") -U_("initial") =0`.