What is PV diagram?
The diagram which shows variation in the pressure and volume of a working substance during any process is known as the Pressure Volume or PV diagram. Let us discuss the PV diagram for Carnot cycle.
PV diagram for Carnot cycle

Figure shows variation in pressure and volume of the working substance during various processes of a Carnot cycle
In the PV diagram of a Carnot engine, the X-axis represents Volume and the Y- axis represents the pressure
With reference to the PV diagram for carnot cycle
- T1 & T2 is a Constant temperature line
- Q1=Heat supplied to the engine at a constant temperature “T1”
- Q2=Heat rejected by the engine at a constant temperature “T2”
- a-b = reversible Isothermal expansion process
- b-c = reversible isentropic or adiabatic expansion process
- c-d=reversible isothermal compression process
- d-a = reversible isentropic or adiabatic compression process
- Area under the curve a-b-c-d represents net work done.
If you want to check the PV diagram of the Diesel cycle then click/tap here
If you want to check the PV diagram of the Otto cycle then click/tap here
Piston cylinder arrangement for carnot cycle

About the Carnot Cycle
Carnot cycle is the most efficient cycle compared with any other irreversible engine cycle, If you want to know more about the efficiency of the Carnot cycle then click/Tap here
The carnot cycle can be used for refrigeration. To know how this can be achieved then click/Tap here
In actual practice, using the Carnot cycle to design the engine is impossible. Do you want to know why then click/Tap here
References
Refrigeration and Air Conditioning by C P Arora
Internal combustion engines by M.L. Mathur and R.P. Sharma