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I read that entropy change of universe is zero in a reversible process but positive in a irreversible process,then doesn't it mean that entropy change of system of both the processes must be different?

I also read that in a reversible cycle, entropy change is zero for example a carnot cycle,and entropy change in an irreversible cycle is positive for example if we consider friction in a carnot cycle. Doesn't this show that entropy change of system in both processes is different?

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    $\begingroup$ I don't think I understand your question. But note that the change in entropy is zero for a reversible process, not the entropy itself... $\endgroup$ – lemon Mar 18 '16 at 16:53
  • $\begingroup$ Yes i meant entropy change $\endgroup$ – Raksh23 Mar 18 '16 at 17:10
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    $\begingroup$ Yes... The entropy change for a reversible versus an irreversible process is different (by definition)... $\endgroup$ – lemon Mar 18 '16 at 17:12
  • $\begingroup$ I meant the entropy change in both the processes.We say that entropy change is a state function and hence should not depend on path taken. $\endgroup$ – Raksh23 Mar 18 '16 at 17:13
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    $\begingroup$ That's right, but a reversible process ends up in a different state to an irreversible process, so the paths are necessarily different... $\endgroup$ – lemon Mar 18 '16 at 17:13
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I think entropy change is zero if the system undergoes reversible and adiabatic process at the same time(isentropic process)

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