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One question on average thermal velocity of free electron in metals

  1. Oct 18, 2009 #1
    Hi, I'm a student learning Solid State Physics and in a chapter of Classical Free Electron Theory of Metals in the textbook, it mentions "Since in the absence of a (electric) field there can be no net current, it is clear that the average thermal velocity over the equilibrium (thermal velocity) distribution must be zero." I don't quite understand why it should be zero. Can someone explain this to me?
  2. jcsd
  3. Oct 18, 2009 #2


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    Because if it was not zero charges could accumulate in some part of the metal, which would violate the laws of thermodynamics (and it would also not be a equilibrium state anymore).

    All that statement means is that electrons in a thermal equilibrium are -on average- not going anywhere.
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