Thermal velocity is the velocity of the free electron due to their random motion. So how is the average value 0?

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    $\begingroup$ why should a free electron be more likely to be moving left than right? $\endgroup$ – By Symmetry May 14 '16 at 15:43
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    $\begingroup$ @BySymmetry I love how your username perfectly fits your comment :-P $\endgroup$ – AccidentalFourierTransform May 14 '16 at 15:46
  • $\begingroup$ Gupta ji , If it was not 0, your object will run out of electrons. $\endgroup$ – Anubhav Goel May 14 '16 at 15:57
  • $\begingroup$ I think you are confusing the average velocity (i.e., first velocity moments) with the thermal speed (i.e., can be from the second velocity moment with some assumptions). $\endgroup$ – honeste_vivere May 22 '16 at 18:07

Their average speed would be non zero but their average velocity would be zero as long as they are not moving preferentially in one direction.


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