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Drude formula

by aaaa202
Tags: drude, formula
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Feb5-14, 09:30 AM
P: 1,005
I can't derive it properly even though it should be easy:
From Newtons 2nd law:

m dv/dt = -eE


v(t) = -meEt + v(0) (the latter will average out when taking average)

Now the Drude assumption: An electron will on average travel a time τ before being scattered and starting its motion in the direction of E all over.

Thus this means, I think, that on average an electron will travel with a velocity equal to
<v> = -meEτ/2

And one can then multiply by electron density to get the Drude formula. Problem is the conductivity should not have the factor . Am I not right in thinking that the electron on average will travel at the velocit given above.
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May29-14, 11:21 PM
P: 109
yes, this is an error is the drude formula. I found it many years back too. Apparently it's well known. Ctrl-F error on the wiki article

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