Carnot heat engine simulation

The Carnot cycle is the most efficient engine possible between two temperatures. No real engine, however clever, can beat its efficiency, which depends only on the temperatures of the hot and cold reservoirs.

Interactive, free and runs in your browser. Part of the Thermodynamics simulations.

What you will see

A gas runs through the four strokes of the cycle and traces them on a p–V diagram: an isothermal expansion taking in heat from the hot reservoir, an adiabatic expansion, an isothermal compression giving heat to the cold reservoir, and an adiabatic compression. The enclosed area is the work done per cycle.

Try this

  1. Raise the hot reservoir temperature and watch the loop and the efficiency grow.
  2. Identify which strokes take in heat and which give it out.
  3. Compare the steepness of the adiabats with the isotherms.

Common misconception

A better engine design cannot reach 100% efficiency. The Carnot limit is a law of thermodynamics, not an engineering shortfall: some heat must always be dumped into the cold reservoir.

Exam-style question

What is the maximum efficiency of a heat engine running between 500 K and 300 K?

η = 1 − T_C/T_H = 1 − 300/500 = 0.40, so 40%. Even a perfect engine must reject 60% of the heat it takes in.

Key equations

  • η = 1 − T_C / T_H
  • pVᵞ = constant (adiabatic)
  • W = Q_H − Q_C

Curriculum

AQA A-level physics 3.6.2, IB Physics B.1–B.4.

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