Critical Variable

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:


\left(\frac{\partial P}{\partial V}\right)_{C}=0

\left(\frac{\partial^2 P}{\partial V^2}\right)_{C}=0

For the van der Waals equation, the above yields:


P_C=\frac{a}{27b^2}

\displaystyle{V_C=3nb}

T_C=\frac{8a}{27bR}

Famous quotes containing the words critical and/or variable:

    You took my heart in your hand
    With a friendly smile,
    With a critical eye you scanned,
    Then set it down,
    And said: It is still unripe,
    Better wait awhile;
    Christina Georgina Rossetti (1830–1894)

    There is not so variable a thing in nature as a lady’s head-dress.
    Joseph Addison (1672–1719)