Equilibrium for Systems with Internal Degrees of Freedom

The expressions of equilibrium that have been derived are not terribly profound or useful so far. Another condition of equilibrium that is very useful will be derived below and this is one that you will use over and over again as professional scientists.

Recall that when considering other types of work:

$$\input{equations/dUgen}$$ (18-1)

where $F_i$ were the various forces acting on the system and the $x_i$ were the extensive variables that changed according to those forces. We consider the $V$ and the $x_i$ to be the degrees of freedom associated with the system.