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Isochor

Definition

... a process at constant volume, denoted by a vertical line on a pV diagram and a curve on a Ts diagram.

Where it occurs.

In the theoretical Otto Cycle, heat is added and rejected at constant volume. In the theoretical Diesel Cycle, heat is rejected at constant volume. Constant volume heating/ cooling might also apply to fluid storage tanks.

Special features

If a the volume of a system is fixed, then the system can do no work.

How to draw it

Locate the POI and press the isochor button.

The theory

For an ideal gas at constant volume then temperature is proportional to pressure according to the Gay-Lussac law. Or, from the Ideal Gas Law, $$ T = \frac{ V}{m R} \times p $$ The calculations of ideal gas internal energy, enthalpy and entropy are explained in conjunction with the point of interest.

Exercises

Click on the graph to get a POI and plot an isochor through it. Click along the isochor to set new POIs and note how temperature increases with pressure.

Links

... to follow.