Pressure–volume diagram
diagram in thermodynamics, ploting pressure versus volume, typically used for thermodynamic processes
A pressure–volume diagram (or PV diagram, or volume–pressure loop) is used to describe corresponding changes in volume and pressure in a system. It is commonly used in thermodynamics, cardiovascular physiology, and respiratory physiology.
PV diagrams, originally called indicator diagrams, were developed in the 18th century as tools for understanding the efficiency of steam engines.
Description
A PV diagram plots the change in pressure P with respect to volume V for some process or processes. Commonly in thermodynamics, the set of processes forms a cycle, so that upon completion of the cycle there has been no net change in state of the system; i.e. the device returns to the starting pressure and volume.
The figure shows the features of an idealized PV diagram. It shows a series of numbered states (1 through 4). The path between each state consists of some process (A through D) which alters the pressure or volume of the system (or both).
A key feature of the diagram is that the amount of energy expended or received by the system as work can be measured because the net work is represented by the area enclosed by the four lines.
“Pressure–volume diagram” enters the record as diagram in thermodynamics, ploting pressure versus volume, typically used for thermodynamic processes. Crown Archives preserves that source wording while asking what Pressure, volume and diagram can confirm, complicate or overturn.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Jul 9, 2025. The linked authority identifier is Q311318. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “Pressure–volume diagram” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.