# Gibbs free energy (when charge is passed in a battery)

## Description

The Gibbs free energy is a thermodynamic potential that measures the “usefulness” or process-initiating work obtainable from a thermodynamic system, at a constant temperature and pressure (isothermal, isobaric). When multiplied by an amount of charge the emf (electromotive force) yields a thermodynamic work .

Related formulas## Variables

G | Free energry (J) |

S | Entropy (J/K) |

T | Absolute temperature (K) |

p | Pressure of the system (Pa) |

V | Volume of the system (m^{3}) |

ϵ | Electromotive force (V) |

Q | Charge (C) |