Thermodynamics | Reversible and Irreversible Processes#
Irreversible Process#
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An irreversible process is a type of process in which the driving force is much greater than the opposing force.
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It is a very fast process and takes a very little time to complete.
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In case of irreversible expansion, Pgas is much greater than Pext (Pgas >> Pext).
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In case of irreversible compression, Pext is much greater than Pgas (Pext >> Pgas).
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Work done in an irreversible process is given by:
Since, irreversible processes take place against constant external pressure.
Reversible Process#
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In a reversible process, the driving force is infinitesimally greater than the opposing force.
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If the opposing force is increased by an infinitesimally small amount, the process returns back to its previous state. Therefore, it is called reversible.
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Reversible processes are generally very slow processes.
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For a reversible expansion, Pgas is infinitesimally greater than Pext.
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For a reversible compression, Pext is infinitesimally greater than Pgas.
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In general, we can write: Pext ≈ Pgas
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Work done in a reversible process is given by:
Since, Pext ≈ Pgas, we can write: