Just sharpening up on my thermo again. In the carnot cycle, since the first two stages involve successive pressure drops, 1st from isothermal expansion, 2nd from adiabatic expansion, am I to understand that at the end of those two steps, when the piston has stopped moving, i.e. expansion ends, that the pressure of the gas in the chamber is exactly equal to atmospheric pressure and that therefore at the beginning of the cycle the gas must first quickly be heated to a pressure above atmospheric.

If this is the case then I'm assuming that the work calculation done cannot involve an equation of state substitution since the pressure in the chamber IS NOT equal to the external pressure it's doing work against. Unless I'm totally wrong.

Can anyone clarify?

Cheers,

Renai