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Fluids

Isobaric process

Isobaric stems from the Greek words ισος (isos = equal) and βαρυς (barys = heavy). An isobaric process is a thermodynamic process in which the pressure stays constant.
Consider for example a quantity of an ideal gas in a container under a freely movable piston.
When that system is heated then, according to Charles's law (also known as the law of volumes), the volume of the gas increases, whereas the pressure P stays constant. When, moreover, the piston is connected to a machine, e.g. the wheels of our vehicle, then the gas performs work by moving our vehicle.

The above process is shown in the following pressure-volume diagram where we consider an increase in volume from V₁ to V₂.



While increasing the volume of the gas the piston moves which allows work to be done by the gas. The total amount of work W_1→2 done by the gas can easily be determined from

W_1→2 = P×ΔV = P×(V₂-V₁)

The above process is an example of how heat can be transformed into the work needed for machines to run.

isochoric process