🔥 Carnot Engine

📖 The Physics

A Carnot engine is the ideal, most efficient heat engine possible. It takes in heat Qh from a hot reservoir, converts part of it into useful work W, and dumps the rest Qc into a cold reservoir.

Its four reversible steps — heat in (red), adiabatic expansion (grey), heat out (blue), adiabatic compression — form a closed loop, and the area enclosed by the loop is the work done per cycle.

Efficiency depends only on the two temperatures. Raise Th or lower Tc and the loop fattens and η climbs — but η = 100% would need Tc = 0 K, which is impossible (the second law of thermodynamics).