A gas in a rigid tank (constant volume) is heated. No work is done because (dV=0). Therefore, (Q = \Delta U)—all heat added increases the internal energy (temperature or phase).
| Device | What happens to $Q$? | What happens to $W$? | | :--- | :--- | :--- | | | Heat is added from fuel ($+Q$) | Piston expands, doing work on crankshaft ($-W$) | | Refrigerator | Heat is pulled from inside ($-Q$) | Compressor does work on refrigerant ($+W$) | | Turbine | Heat added from boiler ($+Q$) | Blades spin, doing work to generator ($-W$) | engineering thermodynamics work and heat transfer
). In thermodynamics, we often think of it as the energy required to move a piston or turn a shaft. A gas in a rigid tank (constant volume) is heated
Despite both being modes of energy transfer, work and heat are fundamentally different: | Device | What happens to $Q$