Heat and Thermodynamics

10.1 Maxwell's Relations

The two fundamental principles of thermodynamics are as follows:

1. The first law of thermodynamics represented by the energy equation

    

   dQ = dU + dW     (10.1)

    

2. The second law of thermodynamics represented by the equation of Clausius

    

   dQ = TdS     (10.2)

In these equations, the quantities U, W and S are functions of the thermodynamic co-ordinates p, v and T of which only two are independent variables. From these equations, other useful relations between the four co-ordinates p, v, T and S can be obtained. Out of these four co-ordinates, only two can vary independently. Hence, any two of these co-ordinates only can be expressed in terms of the remaining two co-ordinates. The equations thus obtained are called Maxwell's ...