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If we increase the diameter of a wire, does the electron density change at all? When we increase the diameter or the length of a wire (while solving numericals) do we add appropriate number of electrons so that the electron density doesn't change?

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  • $\begingroup$ Unless you make very small wires where surface effects overwhelm bulk physics, the electron density will be basically the same. The number of electrons is simply proportional to the volume of the metal. $\endgroup$
    – CuriousOne
    Feb 3, 2016 at 18:31
  • $\begingroup$ As CuriousOne has noted the electron density is mainly dependent on the material under normal circumstances $\endgroup$
    – Jaywalker
    Feb 3, 2016 at 18:41
  • $\begingroup$ A question is what you want to do with the answer. E.g., is it to consider electrons available to conduct electric current ? maybe, alternate current at possibly high frequency ? It would give a different answer. $\endgroup$ Feb 5, 2016 at 23:54

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Electron density is a property of the material - same as the mass density. If you have a wire made out of copper, there will be more copper atoms in a thick wire than in a thin one - but the same number of electrons per atom.

So unless you change the composition of your wire, the electron density (number of electrons per unit volume) stays the same.

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