THM-29

Helmholtz energy

Isochoric-isothermal potential.

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GoverningHelmholtz energy

Governing equation

F=U-TS

where

U: U (kJ)
T: T (K)
S: S (kJ/K)
F: Helmholtz energy (kJ)

Lecture brief

Historical brief

Carnot (1824), Clausius entropy, the first law and later van der Waals and Gibbs potentials turned heat into a state science. The sheets compute work, efficiency and vapour pressure. This sheet (THM-29 — Helmholtz energy) is the form associated with Helmholtz energy. Working symbols: $U$ , $T$ , $S$ $\rightarrow$ $F$ . Isochoric-isothermal potential. Pedagogical SI sheet with a live model and a swept parameter.

Purpose

Purpose: compute

F

from

U

T

S

in Thermodynamics via

F=U-TS

Isochoric-isothermal potential. Use it when a real thermodynamics question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

U = 180.000\,\mathrm{kJ}

T = 298.000\,\mathrm{K}

S = 0.400\,\mathrm{kJ/K}

, the governing relation

F=U-TS

yields

F = 60.800\,\mathrm{kJ}

. One governing identity, SI units, a single sweep on the sheet. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

U U180 kJT T298 KS S0.4 kJ/K

Outputs

Helmholtz energy F60.800 kJ

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Narration of this film

One governing identity, SI units, a single sweep on the sheet.

Isochoric-isothermal potential. Pedagogical SI sheet with a live model and a swept parameter.

Reading speed

Watch on YouTube