According to the question Why is charge = nALe n is the charge density (number of electrons per unit volume). Which of the electrons in a metal wire are involved in current flow? Only the unbounded to the nucleus (electron gas) I suppose. Or only some part of them? What is the amount for a cooper wire?

  • $\begingroup$ All electrons in a metal are bound. If they weren't bound, they would just fly away. $\endgroup$ – CuriousOne May 1 '15 at 6:16
  • $\begingroup$ @CuriousOne: Then to talk about free electrons in metal is not correct too :-). I expand my question. $\endgroup$ – HolgerFiedler May 1 '15 at 6:20
  • $\begingroup$ @CuriousOne: How you would call such electrons? $\endgroup$ – HolgerFiedler May 1 '15 at 6:23
  • $\begingroup$ Hmmm... free... bound... free... bound... valence band... conduction band... not the same words, not even in the dictionary, let alone in a physics textbook. Just curious... did you ever look into a physics textbook or are you just making it up as you go? $\endgroup$ – CuriousOne May 1 '15 at 6:24
  • $\begingroup$ @CuriousOne: slhulk has ut's one wirds for this electrons. So it seems not as easy as you suggested. What is about to call them "valence electrons"? $\endgroup$ – HolgerFiedler May 1 '15 at 9:10

Current is conducted due to loosely held electrons present in a metallic lattice. (refer metallic bond on wiki). Note the electrons are loosely held to the neucleus and they are not free to fly away. When a potential difference is applied across a metallic conductor these electrons move from low potential to high potential giving rise to an electric current in the opposite direction (according to the convention). Note that, all the electrons in the conductor experience this at the same time, and hence a neglegible time is needed to light a light bulb (although the drift velocity of electrons is very low). Hope this will help.:)

  • $\begingroup$ I'm really need the amount in cooper wire. When I'm back in office I'll find the paper in which I've seen this number and will post it. $\endgroup$ – HolgerFiedler May 1 '15 at 9:13
  • $\begingroup$ They are NOT valence electrons. In general they are reffered to as 'free electrons' contrary to the literal meaning they are not so free to move. They are loosely held by the neucleus. They are present in mettalic bonds and are absent in ionic or covalent bonds $\endgroup$ – slhulk May 1 '15 at 9:28
  • $\begingroup$ To help with your calculation. We have Q=Vne where Q is the charge flown, V is the volume of the rod, n is the electron density and e is the charge of an electron. Thus by substituting values for each u can find n $\endgroup$ – slhulk May 1 '15 at 9:33
  • $\begingroup$ Or u can use I=Anev where I is the current through the conductor, A is the area, n electron density, e charge of one electron, v is the drift velocity of electrons inside the conductor $\endgroup$ – slhulk May 1 '15 at 9:35
  • $\begingroup$ But then I need the drift velocity. And some difficulties I see because the drift velocity clearly depends from the current. $\endgroup$ – HolgerFiedler May 1 '15 at 9:54

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