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Banner logo[Help with translations!]Hide Quasistatic process From Wikipedia, the free encyclopedia Jump to navigationJump to search Thermodynamics Carnot heat engine 2.svg The classical Carnot heat engine Branches Laws Systems System properties Material properties Equations Potentials HistoryCulture Scientists Other Category Category vte In thermodynamics, a quasi-static process (also known as a quasi-equilibrium process. From the Latin quasi, meaning ‘as if’[1]), is a thermodynamic process that happens slowly enough for the system to remain in internal thermodynamic equilibrium. An example of this is quasi-static expansion, where the volume of a system changes so slowly that the pressure remains uniform throughout the system at each instant of time during the process.[2] Such an idealized process is a succession of equilibrium states, characterized by infinite slowness.[3]

Only in a quasi-static process can we exactly define intensive quantities (such as pressure, temperature, specific volume, specific entropy) of the system at every instant during the whole process; otherwise, since no internal equilibrium is established, different parts of the system would have different values of these quantities.

The theoretical term 'reversible process' is sometimes used. It refers to a theoretically convenient idealization that can in practice be realized only approximately, for exactly reversible processes are ruled out by the second law of thermodynamics. For example, slow compression of a system by a piston subject to friction is irreversible; although the system is always in internal thermal equilibrium, the friction ensures the generation of dissipative entropy, which goes against the definition of reversible. Any engineer would remember to include friction when calculating the dissipative entropy generation. An example of a slow process that is not even idealizable as reversible is slow heat transfer between two bodies on two finitely different temperatures, where the heat transfer rate is controlled by a poorly conductive partition between the two bodies— in this case, no matter how slowly the process takes place, the states of the composite system consisting of the two bodies is far from equilibrium, since thermal equilibrium for this composite system requires that the two bodies be at the same temperature.

PV-Work in various quasi-static processes Main articles: Work (thermodynamics) and Ideal gas equation Constant pressure: Isobaric processes, {\displaystyle W_{1-2}=\int PdV=P(V_{2}-V_{1})}W_{1-2}=\int PdV=P(V_{2}-V_{1}) Constant volume: Isochoric processes, {\displaystyle W_{1-2}=\int PdV=0}W_{1-2}=\int PdV=0 Constant temperature: Isothermal processes, {\displaystyle W_{1-2}=\int PdV,}W_{1-2}=\int PdV, where P varies with V via {\displaystyle \quad PV=P_{1}V_{1}=C}\quad PV=P_{1}V_{1}=C, so {\displaystyle W_{1-2}=P_{1}V_{1}\ln {\frac {V_{1}}{V_{2}}}}{\displaystyle W_{1-2}=P_{1}V_{1}\ln {\frac {V_{1}}{V_{2}}}} Polytropic processes, {\displaystyle W_{1-2}={\frac {P_{1}V_{1}-P_{2}V_{2}}{n-1}}}W_{1-2}={\frac {P_{1}V_{1}-P_{2}V_{2}}{n-1}} See also Entropy Reversible process (thermodynamics) References Lewis, C.T., Short, C. (1879). A Latin Dictionary, Clarendon Press, Oxford, page 1507. Schroeder, Daniel (2000). An Introduction to Thermal Physics. United States: Addison Wesley Longman. pp. 20–21. ISBN 0-201-38027-7. Rajput, R.K. (2010). A Textbook of Engineering Thermodynamics, 4th edition, Laxmi Publications (P) Ltd, New Delhi, pages 21, 45, 58. Categories: Thermodynamic processesStatistical mechanics Navigation menu Arshvard Alert (1) Notice (1) Talk Sandbox Preferences Beta Watchlist Contributions Log out ArticleTalk ReadEdit sourceView historyWatchSearch Search Wikipedia Main page Contents Current events Random article About Wikipedia Contact us Donate Contribute Help Learn to edit Community portal Recent changes Upload file Tools What links here Related changes Special pages Permanent link Page information Cite this page Wikidata item Print/export Download as PDF Printable version

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