Topic
Thermal Physics
From microscopic motion and temperature to heat, work, entropy and the limits of thermal machines.
Start Here
- Temperature, Heat, and the Ideal-Gas BridgeTemperature, heat, and internal energy answer different questions. Their separation is what allows thermal physics to extend mechanics rather than replace it.
Go Deeper
- The First Law: Why the Path MattersEnergy conservation becomes thermodynamics when we specify a system boundary and distinguish energy transfer as heat from energy transfer as work. For a closed system with negligible changes in bulk kinetic and gravitational potential energy, use
- Entropy and Heat Engines: Why Conserved Energy Is Not All UsableThe statistical entropy entry explains why macrostates with many compatible microstates are overwhelmingly favored. Here the aim is operational: calculate entropy changes and use them to decide whether an energy-conserving machine is possible.