Critical variable
(Redirected from Critical variables)
Critical variables are defined, for example in thermodynamics, in terms of the values of variables at the critical point.
On a PV diagram, the critical point is an inflection point. Thus:
- <math>
\left(\frac{\partial P}{\partial V}\right)_{C}=0 <math>
- <math>
\left(\frac{\partial^2 P}{\partial V^2}\right)_{C}=0 <math>
For the van der Waals equation, the above yields:
- <math>
P_C=\frac{a}{27b^2} <math>
- <math>
v_C=3b <math>
- <math>
T_C=\frac{8a}{27bR} <math>
Categories: Thermodynamics