Physics 4 — Thermo & Fluids

Carnot — the law nobody beats

continues from lesson 2 — values defined earlier in the course stay live here

No engine converting heat to work can beat η = 1 − T_cold/T_hot (temperatures in kelvin). Not with better materials, not with cleverness — it is bookkeeping on entropy itself. A car engine:

T_{hot} = 800

combustion (K)

T_{cold} = 300

exhaust to ambient (K)

\eta_{carnot} = 1 - \frac{T_{cold}}{T_{hot}}

0.6250

62.5% — the unbeatable ceiling

✓ pass

\eta_{carnot} < 1

a perfect heat engine is impossible — always

Real engines manage ~25–35%. The gap between that and 62.5% is friction and irreversibility; the gap between 62.5% and 100% is the second law.