An ideal gas expands isothermally from a volume V1 to V2 to and then compressed to original volume V1 adiabatically. Initial pressure is P1 and final pressure is P3. The total work done is W. Then
From graph it is clear that P3>P1.
Since area under adiabatic process (BCED) is greater than that of isothermal
process (ABDE). Therefore net work done
W=Wi+(−WA)∵WA>Wi⇒W<0