- #36
Naty1
- 5,606
- 40
mpatryluk...
in case you are still around...and I would not blame you based on the discussion so far if you gave up...
I assume you are starting out with electrical circuits, and if so the discussions so far probably haven't helped much.
I don't understand 3/4 of the drivel posted so far...sophiecentaur being the exception.
I would paraphrase his comments as saying "Such a model [posted by others] of charge distribution, integrals, Gauss' law,etc, are unnecessarily abstract in a circuit analysis like this." At least that's what I think. I'll stick with what I posted already, but here are some additional ways to think in more concrete terms...maybe less abstract than I posted...
why voltage changes along a resistor:
think of voltage as the difference in electric potential energy of a unit charge, one electron, say, transported between two points. [That potential difference comes from some source, say, electro chemicial [battery] or maybe a dc generator. For a chemical viewpoint, you can look up stuff like 'redux reactions' or 'battery', say via Wikipedia.]
These individual electrons are what move along in lock step in a typical conductor...and resistor...loosly bound electrons, called 'conduction electrons', 'valence electrons' or whatever, in a conductor, more tightly bound electrons in a resistor...'More tightly bound' means a stronger local bond to an atom or other material structure...so it takes more potential [electrical energy] to dislodge them.
[An insulator, like ceramic or rubber or plastic has really tightly bound electrons and will not let them move easily...electrons can't move, so they resist any current flow because their electrons 'stay in place'. Circuit designers like insulators because they don't waste power! ]
think of circuit electrons in this simplified analogy as maybe cars lined up on ahighway...as you move one, then two, then three, as moving along in a resistor, it takes more and more work to overcome friction, analogous to individual electron attraction in a typical resistor...So as you move your voltmeter further and further apart over the length of a resistor to measure voltage, you encounter more and more displaced electrons, each with a tiny electric potential difference, and they each add up.
But this has nothing to do with any 'distribution of charge'...the same number of electrons entered one end of the resistor as emerged from the other end...each moves along like a line of cars on the highway...individual electrons 'drift' from atom to atom rather slowly, but as one enters, another leaves at a distant point, pushed along by the potential difference of all the intermediate electrons.
So while electric current is really fast overall, but not light speed, individual electrons in a typical circuit bump along at a only few meters per second...it's called 'electron drift velocity' like cars stuck on a highway moving slow, like 10mph in heavy traffic, yet one enters and one exits miles apart giving the appearance of rapid transport.
Hope that helps...
in case you are still around...and I would not blame you based on the discussion so far if you gave up...
I assume you are starting out with electrical circuits, and if so the discussions so far probably haven't helped much.
I don't understand 3/4 of the drivel posted so far...sophiecentaur being the exception.
I would paraphrase his comments as saying "Such a model [posted by others] of charge distribution, integrals, Gauss' law,etc, are unnecessarily abstract in a circuit analysis like this." At least that's what I think. I'll stick with what I posted already, but here are some additional ways to think in more concrete terms...maybe less abstract than I posted...
why voltage changes along a resistor:
think of voltage as the difference in electric potential energy of a unit charge, one electron, say, transported between two points. [That potential difference comes from some source, say, electro chemicial [battery] or maybe a dc generator. For a chemical viewpoint, you can look up stuff like 'redux reactions' or 'battery', say via Wikipedia.]
These individual electrons are what move along in lock step in a typical conductor...and resistor...loosly bound electrons, called 'conduction electrons', 'valence electrons' or whatever, in a conductor, more tightly bound electrons in a resistor...'More tightly bound' means a stronger local bond to an atom or other material structure...so it takes more potential [electrical energy] to dislodge them.
[An insulator, like ceramic or rubber or plastic has really tightly bound electrons and will not let them move easily...electrons can't move, so they resist any current flow because their electrons 'stay in place'. Circuit designers like insulators because they don't waste power! ]
think of circuit electrons in this simplified analogy as maybe cars lined up on ahighway...as you move one, then two, then three, as moving along in a resistor, it takes more and more work to overcome friction, analogous to individual electron attraction in a typical resistor...So as you move your voltmeter further and further apart over the length of a resistor to measure voltage, you encounter more and more displaced electrons, each with a tiny electric potential difference, and they each add up.
But this has nothing to do with any 'distribution of charge'...the same number of electrons entered one end of the resistor as emerged from the other end...each moves along like a line of cars on the highway...individual electrons 'drift' from atom to atom rather slowly, but as one enters, another leaves at a distant point, pushed along by the potential difference of all the intermediate electrons.
So while electric current is really fast overall, but not light speed, individual electrons in a typical circuit bump along at a only few meters per second...it's called 'electron drift velocity' like cars stuck on a highway moving slow, like 10mph in heavy traffic, yet one enters and one exits miles apart giving the appearance of rapid transport.
Hope that helps...