# A Thermodynamics relations

1. May 6, 2017

### LagrangeEuler

Thermal coefficient of pressure is defined by
$$\gamma=\frac{1}{P}(\frac{\partial P}{\partial T})_V$$. Why in books authors uses $\gamma=\gamma(P,T)$ and no $\gamma=\gamma(P,T,V)$. Could you explain me this. I am sometimes confused with this dependences in thermodynamics.

2. May 6, 2017

### Staff: Mentor

From the equation of state, V=V(P,T), so there are really only to independent variables.

3. May 6, 2017

### LagrangeEuler

Ok. Thanks. But why not $\gamma=\gamma(T,V)$?

4. May 6, 2017

### Staff: Mentor

That can be done, but it's not as convenient for calculations.

5. May 7, 2017

### LagrangeEuler

Thanks.

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