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Electron Distribution in a Simple Circuit

  1. Aug 29, 2011 #1
    Hi guys,

    I'm trying break down a simple circuit composed of a lamp and a power source down to it's basics.

    So, I know that the current will flow from negative to positive. However, is it correct to say that there are more electrons before the lamp than there is after the bulb? This difference in concentration of electrons is what causes the voltage across the bulb.

    I know that the electrons will be moving at the same rate at all points in the circuit, but is there a higher concentration of electrons before they "meet" the bulb than after the bulb?

    I know some of you will laugh at such a simple question, but it's something that's been annoying me.
  2. jcsd
  3. Aug 29, 2011 #2


    User Avatar

    Staff: Mentor

    Welcome to the PF.

    No. the current is contiguous. There is a circuit analysis technique that uses this continuity -- it's called Kirchoff's Current Law (KCL). You can look it up on wikipedia.org to learn more...
  4. Aug 30, 2011 #3
    << URL deleted by berkeman >>I hope this qualifies as a valid reference. It has pictures of charge distribution in DC circuits.

    PS: berkeman would you please reply to my pm, thanks
    Last edited by a moderator: Aug 30, 2011
  5. Aug 30, 2011 #4
    Cheers guys.

    I'll definitely take a look at the aforementioned links.
  6. Aug 30, 2011 #5


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    Staff: Mentor

    No, sorry. That self-published paper has problems, so I deleted the reference to it. If you can find a similar paper published in a mainstream peer-reviewed scientific journal, then we will allow it.

    I did reply to your PM just now.
  7. Aug 30, 2011 #6
    "Electric Circuits & Networks" By Suresh Kumar, Kumar K. S. Suresh

    See page 9:
    1.2 "A voltage source with a resistance connected at its terminals",
    1.2.1 "Steady-state charge distribution in the system"
    Figure 1.2-1 "Steady-state with a resistance connected across DC voltage"

    berkeman, this is a textbook, if this does not qualify, I don't know what is.
    Sorry I could not find anything available online in peer-reviewed journals because these kind of things are so basic and well studied they no longer appear in peer-reviewed journals. They do appear in textbooks and teaching aids though.

    I believe Feynman has addressed this subject in his lectures but I do not have access to them at the moment so I cannot quote the exact page/paragraph. I'll look it up later.

    The following papers appear to deal directly with subject, unfortunately I do not have access to them either:
    Rosser, W. G. V., 1963, What makes an electric current “flow”, American Journal of Physics, 31,884 - 885.
    Rosser, W. G. V., 1970, Magnitudes of surface charge distributions associated with electric current flow, American Journal of Physics, 38, 265 - 266.
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