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Second law of thermodynamics - what does it actually mean?

  1. May 25, 2010 #1
    I read in the paper that the 2nd law of thermodynamics says energy is constantly decreasing in a closed system.

    Is that true? I learned the law in my first year of college but I can't remember its implications. Anyway, I can't find a straight 'true' or 'false' answer anywhere, and it's bothering me because I think the paper is wrong :)

    Can anyone explain?
     
  2. jcsd
  3. May 25, 2010 #2

    DaveC426913

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    Eventually, the entire system will reach thermodynamic equilibrium. No differences in temperature = no energy can be extracted.
     
  4. May 25, 2010 #3
    Ah - so the energy is still there, it's just not useful. Is that right?
     
  5. May 25, 2010 #4

    Char. Limit

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    By conservation of energy, the energy must still be there, yes.
     
  6. May 27, 2010 #5
    And energy must always be there, it may get a different form but it is there
     
  7. May 27, 2010 #6

    DaveC426913

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    It may not even be in the different form. Its initial state might simply be an imbalance in heat distribution, which could be extracted to do work. But once the temperature has equalized, there's no way to extract it anymore.
     
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