Thermodynamics — Easy Practice (Set 2)

Quick Recap — Processes, Engines & the Second Law

• Isothermal: $\Delta U = 0$ and $PV =$ constant; adiabatic: $Q = 0$ and $PV^\gamma =$ constant.
• Values of $\gamma$: monatomic $\tfrac53$, diatomic $\tfrac75$.
• Second law: heat flows spontaneously from hot to cold, and no engine can be 100% efficient.
• Heat-engine efficiency $\eta = \dfrac{W}{Q_1} = 1 - \dfrac{Q_2}{Q_1}$; Carnot $\eta = 1 - \dfrac{T_2}{T_1}$ (temperatures in kelvin).
• Refrigerator / heat pump: the coefficient of performance can exceed 1; a Carnot cycle is two isothermals and two adiabatics.