For a system undergoing an infinitesimal reversible process between two equilibrium states, the change in internal energy is
dU = Tds - pdV |
1.155 |
Substituting the first T - dS relation,
|
1.156 |
|
1.157 |
If U = U(T, V), then
|
1.158 |
Comparing Eq. (1.157) with Eq. (1.158),
|
1.159 |
Eq. (1.159) is known as the energy equation.