Heat Engines

The first law and the Carnot limit

An interactive lesson with 8 steps, about 7 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• First law: $\Delta U = Q - W$. Energy is conserved, including heat.
• Engine efficiency = $W/Q_h$. It can never reach 100%.
• Carnot limit: $\eta_\text{max} = 1 - T_c/T_h$, with temperatures in kelvin.

Steps

1. The first law
2. Engine efficiency
3. Can it be perfect?
4. The Carnot limit
5. Running a Carnot cycle
6. Power station
7. Where the heat goes
8. Hotter is better