Sections Key Equations Key Equations 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 change in entropy ΔS= Q T ΔS= Q T 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 Print Share Key Equations Copy and paste the link code above.