Physics

# Key Equations

PhysicsKey Equations

### 12.2First law of Thermodynamics: Thermal Energy and Work

 ideal gas law $PV=NkT PV=NkT$ first law of thermodynamics $ΔU=Q−W ΔU=Q−W$ pressure $P= F A P= F A$ pressure–volume work $W=PΔV W=PΔV$

### 12.3Second Law of Thermodynamics: Entropy

 change in entropy $ΔS= Q T ΔS= Q T$

### 12.4Applications of Thermodynamics: Heat Engines, Heat Pumps, and Refrigerators

 thermal efficiency of a heat engine $Eff= W Q h Eff= W Q h$ work output for a cyclical process $W= Q h − Q c W= Q h − Q c$