Suppose you have a conductor like a wire with current flowing through it, does it make sense to define a notion of surface charge density for it? So, for example can free charge exist on the surface of a wire with current passing through it be AC or DC.

  • $\begingroup$ Your title mentions "charge density" but your text asks about "surface charge density" specifically. Do you mean to only ask about surface charges, or are you interested in bulk charges also? $\endgroup$ – The Photon Mar 3 at 18:44
  • $\begingroup$ I had surface charges in mind when I wrote the question @ThePhoton, but I guess all bulk charges would pass through as current? $\endgroup$ – Buraian Mar 3 at 20:09

It's certainly possible for there to be both a surface charge present, and a current flowing through a conductor.

The surface charge might or might not be the charge that is moving to form the current, though.

For example, any time current flows in a wire that also has a DC voltage relative to another nearby conductor, this will be the case.

  • $\begingroup$ why did you particularly mention DC voltage? @The Photon $\endgroup$ – Buraian Mar 3 at 18:11
  • $\begingroup$ @Buraian Because it's a relatively simple scenario where there is a surface charge on and a current in the same conductor. $\endgroup$ – The Photon Mar 3 at 18:43
  • $\begingroup$ Could you say what is the mechanism for how the surface charge develops due to nearby dc voltage? @The Photon $\endgroup$ – Buraian Mar 3 at 20:11

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