Physics 312 Lecture: "Work done by Thermodynamic Processes" May 7, 1998

The work done by an engine depends on the precise process by which it converts heat into mechanical power
Four types of thermodynamic processes are
- isobaric: pressure remains constant
- isochoric: volume remains constant
- isothermal: temperature remains constant
- adiabatic: no heat enters or leaves the system during the change
One can figure out how much work is done by any process by integrating dW = P*dV during the transition
The Pressure-Volume (PV) diagram serves to illustrate changes in the properties of a system
The work done by a process is equal to the area beneath the process' curve in the PV diagram
Isobaric process does work: W = P (Vf - Vi)
Isochoic process does work: W = 0
Isothermal process does work: W = nRT ln(Vf/Vi)

Adiabatic process does work:

                        X          1 - gamma        1 - gamma
              W =   ---------   (Vf             - Vi         )
                    1 - gamma

 where
                       gamma
              X = P * V               at any point along the curve

The work done by a cyclic process is equal to the area within the closed loop it defines in the PV diagram

This lecture discusses material in Chapter 20 of Serway.