Why Heat Flows

Two Einstein solids sharing energy

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Ways to share $q$ quanta among $N$ oscillators: $\binom{q+N-1}{q}$.
• Energy flows to the split with the most microstates: where the temperatures are equal.
• Temperature is defined by $1/T = \partial S / \partial E$.

Steps

1. Einstein’s solid
2. Three oscillators
3. Sharing between two solids
4. Hot to cold
5. What temperature is
6. A bigger partner