Everything about Helmholtz Free Energy totally explained
In
thermodynamics, the
Helmholtz free energy is a
thermodynamic potential which measures the “useful” work obtainable from a
closed thermodynamic
system at a constant temperature and volume. For such a system, the negative of the difference in the Helmholtz energy is equal to the maximum amount of work extractable from a thermodynamic process in which temperature and volume are held constant. Under these conditions, it's minimized at equilibrium. The Helmholtz free energy was developed by
Hermann von Helmholtz and is usually denoted by the letter
A (from the German “Arbeit” or work), or the letter
F . The
IUPAC recommends the letter
A as well as the use of name
Helmholtz energy;. In
physics, A is called the
Helmholtz function or simply “free energy”.
While
Gibbs free energy is most commonly used as a measure of thermodynamic potential, especially in the field of
chemistry, the
isobaric restriction on that quantity is sometimes inconvenient. For example, in
explosives research, Helmholtz free energy is often used since explosive reactions by their nature induce pressure changes.
Definition
The Helmholtz energy is defined as:
»
where
- A is the Helmholtz free energy (SI: joules, CGS: ergs),
- U is the internal energy of the system (SI: joules, CGS: ergs),
- T is the absolute temperature (kelvins),
- S is the entropy (SI: joules per kelvin, CGS: ergs per kelvin).
Mathematical development
From the
first law of thermodynamics we have:
» Further Information
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