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avorobey
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I've been trying to understand what happens on a microscopic level - in terms of charges and EM fields - in a simple circuit (say a battery with wires to a lightbulb), and I'm finding it pretty difficult. I read these articles that try to untangle the flow of charge from the flow of energy, and claim that the energy from the battery to the lightbulb is carried not by electrons, but by the EM field running _outside_ the wire:
http://amasci.com/elect/poynt/poynt.html
http://science.uniserve.edu.au/school/curric/stage6/phys/stw2002/sefton.pdf
I still think I don't understand how the current gets going. Please help me fill in the gaps (or fix what I already understand wrongly)!
Here're three pictures.
1. We have a battery, two pieces of wire running to its poles, but not connected to it, and a lightbulb and an open switch in series on those wires. My understanding is that the wires are uncharged, and there's no electric field inside the wires (nor magnetic field outside). Because the battery does create an electric field around it, there's a distribution of surface charge on the wires that cancels it out inside the wire.
2. Now we connect the wires to the battery, but the circuit is still open. What happens? Do charges from the battery flow into the wires, making them oppositely charged? Or do the wires remain uncharged on the whole?
3. Now we close the circuit. I know, from articles above, what happens *some time after* this point: there's a steady state in which a surface charge density on the wires creates an electric field both inside and outside; the electric field inside creates the current, the current creates the magnetic field outside, and the electric + magnetic field outside get the EM field going alongside the wire (please correct if anything's wrong). But how does this situation come to be, as a result of closing the circuit? What causes the surface charge densities on the wires? Are the wires as a whole charged or uncharged as the current flows?
Links to any articles/books that describe the whole picture on such a microscopic level would be great, too.
http://amasci.com/elect/poynt/poynt.html
http://science.uniserve.edu.au/school/curric/stage6/phys/stw2002/sefton.pdf
I still think I don't understand how the current gets going. Please help me fill in the gaps (or fix what I already understand wrongly)!
Here're three pictures.
1. We have a battery, two pieces of wire running to its poles, but not connected to it, and a lightbulb and an open switch in series on those wires. My understanding is that the wires are uncharged, and there's no electric field inside the wires (nor magnetic field outside). Because the battery does create an electric field around it, there's a distribution of surface charge on the wires that cancels it out inside the wire.
2. Now we connect the wires to the battery, but the circuit is still open. What happens? Do charges from the battery flow into the wires, making them oppositely charged? Or do the wires remain uncharged on the whole?
3. Now we close the circuit. I know, from articles above, what happens *some time after* this point: there's a steady state in which a surface charge density on the wires creates an electric field both inside and outside; the electric field inside creates the current, the current creates the magnetic field outside, and the electric + magnetic field outside get the EM field going alongside the wire (please correct if anything's wrong). But how does this situation come to be, as a result of closing the circuit? What causes the surface charge densities on the wires? Are the wires as a whole charged or uncharged as the current flows?
Links to any articles/books that describe the whole picture on such a microscopic level would be great, too.