Carnot

Definition

The Carnot cycle is an idealized thermodynamic cycle that provides the maximum possible efficiency for a heat engine. It consists of two isothermal processes and two adiabatic processes.

5 Must Know Facts For Your Next Test

1. The Carnot cycle demonstrates that no real engine can be more efficient than a Carnot engine operating between the same two temperature reservoirs.
2. The efficiency of a Carnot engine depends only on the temperatures of the hot and cold reservoirs: $\eta = 1 - \frac{T_C}{T_H}$, where $T_C$ and $T_H$ are in Kelvin.
3. The Carnot cycle consists of four stages: isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression.
4. During the isothermal processes in the Carnot cycle, heat transfer occurs at a constant temperature.
5. The second law of thermodynamics states that it is impossible to construct an engine that operates on the Carnot cycle and has 100% efficiency.

Review Questions

• What are the four stages of the Carnot cycle?
• Why can't any real engine be more efficient than a Carnot engine?
• How does temperature affect the efficiency of a Carnot engine?

Related terms

Second Law of Thermodynamics: States that total entropy can never decrease over time for an isolated system; it also implies that perpetual motion machines are impossible.

Isothermal Process: A thermodynamic process in which the temperature remains constant while heat is transferred in or out of the system.

Adiabatic Process: A thermodynamic process in which no heat is exchanged with the surroundings; all energy transfer occurs as work.