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 tgas will be:

Options

A. zero in all the four cases
B. positive in cases (i), (ii) and (iii) but zero in case (iv)
C. positive in all the cases (i) to (iv)
D. negative in cases (i), (ii) and (iii) but zero in case (iv)

Answer

A

Explanation

The processes given in all the four figures, are cyclic processes. Change in internal energy in any cyclic process is zero.