The relation between Internal Energy and Adiabatic constant γ is

we know, internal energy dU=nCvdT U2-U1=nCv(T2-T1) if T1=0⇒U1=0    then ⇒U2=nCvT2 ⇒U=nCvT from PV=nRT⇒PVR=nT and Cv=Rγ-1substitute in above equation ⇒U=PVRRγ-1 U=PVγ-1