Fig 2
A graph of pressure versus volume for a constant-pressure, or isobaric process. The area under the curve equals the work done by the gas, since W=PΔV.
Source
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"OpenStax College, The First Law of Thermodynamics and Some Simple Processes. February 5, 2013."
http://cnx.org/content/m42233/latest/
OpenStax CNX
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