In an adiabatic process we know there is no change in enthalpy or basically enthalpy change is zero. which means any external work done the internal energy does equal opposite work so as to keep $dH=0$. which means in adiabatic process the pressure and temperature have to change. but while deriving the equation for adiabatic process why do we say that $cp=cv+R$ when this can only be true for isobaric process where pressure is constant and also we introduce the term $cp/cv$ being a constant value called adiabatic constant, my question is why do we even use cp value here while clearly in the adiabatic process pressure is not constant.
Where am I going wrong? Am I wrong here because $cp=cv+R$ is true for all processes but I thought it is only true for isobaric process.
Thermodynamics – Why is $c_p/c_v$ Term Introduced in Adiabatic Process?
adiabaticpressuretemperaturethermodynamics
Best Answer
Let me try to clarify a few key points.