The 1st Law for Ideal Gases Reference Page
The Isochronicles: This First Law Saga Is a Gas

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Intro to The 1st Law for Ideal Gases

Ideal gases provide one of the simplest and most useful applications of the First Law of Thermodynamics. Because the thermodynamic properties of ideal gases have simple relationships, many energy balances can be solved analytically.

In particular, the First Law can be applied to several important types of processes: constant temperature, constant pressure, constant volume, and constant entropy. These special cases appear frequently in engineering calculations involving compressors, turbines, and expansion processes.

The Isochronicles: This First Law Saga Is a Gas

This video shows how the First Law of Thermodynamics applies to ideal gases undergoing common thermodynamic processes, including isothermal, isobaric, isochoric, and isentropic processes.

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Examples and Definitions

Definitions

Isothermal Process
A constant-temperature process, \(\Delta T = 0\).
Isobaric Process
A constant-pressure process, \(\Delta P = 0\).
Isochoric Process
A constant-volume process, \(\Delta V = 0\).
Isentropic Process
A constant-entropy process, \(\Delta S = 0\).

Historically, Clausius used the term to refer to processes that are adiabatic and reversible, and most thermodynamics texts still use the term in that sense.