One mole of an ideal gas (γ = 1.4) is adiabatically compressed to half its volume. The ratio of final to initial temperature is approximately:

The Carnot cycle alternates two isothermal steps (heat absorbed at T_H, released at T_C) with two adiabatic steps (no heat exchange); the enclosed loop area equals the net work output, and η = 1−T_C/T_H is the maximum possible efficiency between those two temperatures.