# Electron Distribution in a Simple Circuit

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.

berkeman
Mentor
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.

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...

<< URL deleted by berkeman >>I hope this qualifies as a valid reference. It has pictures of charge distribution in DC circuits.

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Cheers guys.

I'll definitely take a look at the aforementioned links.

berkeman
Mentor
<< URL deleted by berkeman >>I hope this qualifies as a valid reference. It has pictures of charge distribution in DC circuits.

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.

"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.