Carnot Cycle on Ideal Gas
The Carnot cycle is an idealization for a heat engine operating reversibly between two reservoirs at temperatures T1 and T2. The working substance is assumed to be one mole of an ideal gas with heat-capacity ratio γ = CP/CV. (For a monatomic ideal gas, γ has its maximum value at 5/3 = 1.667.) The four steps of the cycle are most commonly plotted on a pressure-volume diagram, shown on the left, with alternate isotherms (red curves of constant temperature) and adiabatics or isentropics (blue curves of constant entropy). A simple alternative representation is therefore a rectangle on a temperature-entropy diagram, shown as an inset.