# Helmholtz free energy

From AMS Glossary

## Helmholtz free energy

(

*Also called*Helmholtz function, work function.) A thermodynamic function of state that, in a reversible isothermal process, increases with work done on the system.In typical notation the Helmholtz free energy is where where

*F*is the Helmholtz free energy (sometimes designated as*A*),*U*is the internal energy,*T*is temperature, and*S*is the entropy. By use of the first law of thermodynamics for reversible processes, the rate of change of the Helmholtz free energy is given by*W*is the work done by the system.*Compare*Gibbs function.