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The ‘Brownian ratchet’ and its relevance to the second law of thermodynamics.

  1. Jun 14, 2012 #1
    My question is regarding the reason why the Brownian ratchet fails to negate the second law.

    The explanation that I have been told relates to the fact that the molecules in the second chamber would interact with the 'pawl' in a similar manner to those interacting with the paddle wheel, negating the overall useful rotation.

    I have also been told that if T1 is higher than T2, then it will produce useful work, but that this complies with the laws by acting like a heat engine.

    My question is: How can the same failure to extract useful work be explained if there was a vacuum in the second chamber? This would negate the temperature comparison, and would seem to allow the extraction of work from the first chamber.

    I would appreciate any available illumination. Thank you.

  2. jcsd
  3. Aug 8, 2012 #2
    I would really like to know this too.
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