Key concept: Work (∆W): Work can be defined as the energy that is transferred from one body to the other owing to a force that acts between them.
If P be the pressure of the gas in the cylinder, then force exerted by the gas on the piston of the cylinder
In a small displacement of piston through dx, work done by the gas
dW = F.dx = PA dx = PdV.
Important point: In a cyclic process work done is
1. positive if the cycle is clockwise.
2. negative if the cycle is anticlockwise.