# Need help understanding a simple circuit in-depth I would like to know more in detail what's really going on in a simple circuit like this. I think I understand it, but I have a lot of things mixed up and others aren't clear to me. I'm going to write an explanation of what I think is right (I know it will contain a lot of mistakes), and I would like if the community could help me understand the things that I have wrong.

So to begin:

The electrons flow from the negative terminal of the battery through the wire to the positive terminal because there is a deficiency of electrons (conventional current goes positive to negative). I think that this deficiency is called the voltage right? So then the battery creates an electric field inside the wire because of the voltage, and for some reason there are surface charges on the wire that help the electrons flow in the correct direction.

I guess my questions in addition to the correction of my explanation are:

1. How does the voltage of the battery relate to the electric field inside the wire?
2. How does the voltage of the battery relate to the surface charges on the wire?
3. What determines the amount of surface charge on the wire? (Why more near the battery, less farther away)

Finally am I missing anything in my understanding?

• This might be a bit too broad of a set of questions to be reasonably answered here. You might want to consider breaking them up into one or two extra posts. – Kyle Kanos Mar 26 '15 at 0:48
• @KyleKanos how would you recommend I go about doing that? – m0meni Mar 26 '15 at 0:50
• You mean besides the obvious Click "Ask Question" and write? That I'm not sure, I just wrote what I thought: that the set of questions might be a bit too much; we generally prefer one question per post (though you can usually get away with two closely related questions, more than that usually doesn't bode well). – Kyle Kanos Mar 26 '15 at 0:56

## 1 Answer

A few points of confirmation/correction:

Yes the electrons flow in a direction opposite to the "conventional" current.

No there is no "deficiency" if electrons - rather they have a different "potential" which is caused by the chemical reactions in the battery.

No you don't have to invoke "surface charges" in the wire in order to understand current - electrons are free to move inside a wire.

Yes there is an electric field pointing along the wire - this is what pushes the electrons while the resistance of the wire is slowing them down.

Think of potential in this circuit like a ramp with marbles on it - the battery is an elevator and the slope of the ramp is the electric field. Marbles roll down the slope and are lifted up again by the voltage source.

If you had a capacitor rather than a battery, the potential difference would indeed be caused by and excess of electrons on one plate (the negative one) and a lack of electrons on the positive one.

• What about voltage makes the electrons move. I understand voltage is potential, but what makes that potential actually do something. Is voltage the manifestation of the electric field? – m0meni Mar 26 '15 at 1:05
• Yes - voltage is the integral of the electric field. If you like, you can say (following the analogy above) that the electric field is the slope of the ramp - the voltage is how high the ramp is. If your ramp is steeper (higher electric field) then for the same distance it climbs more (higher voltage). – Floris Mar 26 '15 at 1:08
• So then is voltage also dependent on some distance, and if so what is that distance? – m0meni Mar 26 '15 at 1:09
• No - the voltage is given by the chemistry of the battery. The electric field is given by the distance over which the voltage drop occurs. – Floris Mar 26 '15 at 1:11
• Thank you so much you've helped me so much. My nobel prize will be dedicated to Floris ;) – m0meni Mar 26 '15 at 1:30