Bridgman's thermodynamic equations

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In thermodynamics, Bridgman's thermodynamic equations are a basic set of thermodynamic equations, derived using a method of generating multiple thermodynamic identities involving a number of thermodynamic quantities. The equations are named after the American physicist Percy Williams Bridgman. (See also the exact differential article for general differential relationships).

The extensive variables of the system are fundamental. Only the entropy S , the volume V  and the four most common thermodynamic potentials will be considered. The four most common thermodynamic potentials are:

Internal energy	U
Enthalpy	H
Helmholtz free energy	A
Gibbs free energy	G

The first derivatives of the internal energy with respect to its (extensive) natural variables S  and V  yields the intensive parameters of the system - The pressure P  and the temperature T . For a simple system in which the particle numbers are constant, the second derivatives of the thermodynamic potentials can all be expressed in terms of only three material properties

heat capacity (constant pressure)	CP
Coefficient of thermal expansion	α
Isothermal compressibility	βT

Bridgman's equations are a series of relationships between all of the above quantities.