Work done in cyclic process I have been told that when $\Delta V=0$, work done will be zero $(W=0)$. I know that, in cyclic process $\Delta V$ will be zero, since it's a path function and $\mid W \mid$ i.e. magnitude of work done will be the area enclosed by the curve. But my doubt is when $\Delta V=0$, shouldn't $W$ also be zero in such processes?
The reversible work is $W=\int{PdV}$ over the path of the process.  This integral is not zero for the cyclic process (involving V changing) even through $\Delta V$ from beginning to end of the process is zero.  So, whoever told you that $W = 0$ when $\Delta V=0$ is wrong.