# Working with Maxwell's equations

1. Feb 9, 2015

### AndrewBworth

Hello all - I've been trying to work out an example from a book, and I don't quite understand the math.

show that (δT/δV)s = - (δP/δS)v

solution (δ/δV (δU(S,V)/δS)v)s = (δ/δS(δU(S,V)/δV)s)v
(δ/δV (δ(TdS - PdV)/δS)v)s = (δ/δS(δ(TdS-PdV)/δV)s)v
(δT/δV)s = -(δP/δS)v

I don't understand the substitution or the last step

2. Feb 9, 2015

### Staff: Mentor

I don't understand the notation. The way I learned it is as follows:

$dU=TdS-PdV$

We must also have that:

$$dU = \left(\frac{\partial U}{\partial S}\right)_VdS+\left(\frac{\partial U}{\partial T}\right)_SdV$$

Therefore, comparing both equations, we have:

$$T=\left(\frac{\partial U}{\partial S}\right)_V$$
$$-P=\left(\frac{\partial U}{\partial T}\right)_S$$

3. Feb 9, 2015

### AndrewBworth

Right I don't understand it either they've inserted the differential expression into a partial fraction I don't know how to work with it.

4. Feb 9, 2015

### Staff: Mentor

So their notation in hinky. Can you get to the final result from my last two equations?

Chet

5. Feb 9, 2015

### AndrewBworth

Sure no sweat.

6. Feb 9, 2015

### AndrewBworth

Ah I figured it out