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Reversible vs. pseudostatic processes

  1. Nov 2, 2010 #1
    I wonder whether a reversible process has to be quasistatic or at least
    pseudostatic? (probably there exist some processes involving magnetic field
    which are reversible but not pseudostatic).

    Below I define what I mean by a reversible, quasistatic and pseudostatic process.

    Reversible process - let's consider a process R in which initial state of the system
    was a, initial state of the environment was b and final state of the system and
    environment was a' and b' appropriately. If there exists a process which
    changes the state of full system (considered system + environment)
    form (a',b') to (a,b) the process R is said to be reversible.

    Pseudostatic process - this is a process during which it may be
    assumed that both the system and its surroundings maintain thermal equilibrium
    (the changes are made sufficiently slow).

    Quasistatic process - this is such a pseudostatic process that in any moment
    if we slightly change some of the external factors which cause it (pressure,
    magnetic field, ...) we can reverse its direction.

    Thanks for any answers.
  2. jcsd
  3. Nov 2, 2010 #2


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    So, I think the notion of 'pseudostatic' is in the context of a time scale slow relative to the internal dynamics of the system. This is a thermodynamic concept, so you cannot talk about whether changes in magnetic fields are reversible or pseudostatic, because in that case you are presumably only considering a single degree of freedom. Heating materials, allowing gases to expand, (de)magnetizing ferromagnets- in these systems the notion of reversible and pseudostatic is applicable, because as you change the bulk thermodynamic properties (T, rho, M respectively), the internal dynamics of the system allow the multitude degrees of freedom of adjust accordingly to 'catch up' with these bulk changes and come back into equilibrium. This usually is not so slow, so a pseudostatic process is quite fast by human time scales.
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