A source I am studying says that the average drift speed of electrons in a thicker wire is less than that in the thin wire. Wouldn't this contradict the fact that thicker wires imply less resistance since what the source implies is that as drift speed decreases, resistance increases?

Also, shouldn't the number density of free electrons in a thick wire be less than the the density of free electrons in a thin wire (as the volume and/or cross sectional area in the thicker wire is greater)?

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    $\begingroup$ What source? Now, what causes drift (vs diffusion) of electrons, and how is that changing in different wires? And, why should the number density of electrons be different in two wires of the same material? $\endgroup$ – Jon Custer Nov 6 '17 at 15:12
  • $\begingroup$ The drift is created by a current through the wires in a series circuit. Shouldn't the number density of electrons in the thicker wire be less as the same number of electrons that would otherwise pass through the thin wire now have a greater cross-sectional area to pass through? $\endgroup$ – A.Sa Nov 6 '17 at 16:31
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    $\begingroup$ No, carrier drift is driven by the electric field. Current is a result of that drift. The number density of free electrons in a given material is constant, regardless of cross-sectional area - it is a property of the material. You still have not stated your source. $\endgroup$ – Jon Custer Nov 6 '17 at 16:37
  • $\begingroup$ Why should the number density of electrons change with the diameter of the wire?... I agree with Jon Custer : If you are questioning a textbook you should give the title and author and upload an image of the text. Probably the text is comparing wires carrying the same current. $\endgroup$ – sammy gerbil Nov 8 '17 at 14:57

Maybe the skin effect is meant here. At high frequencies, the electrons/current are concentrated at the skin, and a thinner wire may have a better average drift since it has more surface per cross area and at the surface/near the surface the drift could be better. But the total resulting apparent resistor should be compared on the basis of the same cross section area, i.e. 1 thick wire compared to n thin wires with the same total cross section.


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