Cyclic Process
A process in which a system undergoes a series of changes and returns to its exact initial state.
Formula / equation
ΔU = 0, q = −w
Unit
J
In depth
Since every state function returns to its starting value, the internal energy change around a complete cycle is zero and any net heat absorbed must equal the net work done. Cyclic operation is what allows engines, refrigerators and heat pumps to work continuously.
Examples in the real world
The four strokes of an internal combustion engine; the compression–expansion cycle of a refrigerator.