I am a high school student and I am very confused in topic "current and electricity" I have read that when any circuit {take a simple one with only one resistor ) is open some charges leaks out from battery and appears as surface charges on the connecting wires which makes up the electric field 0 inside the whole circuit so the potential at any point in the circuit is same as the potential of terminal of the battery to which it is connected, but as soon as we close the circuit those surface charges arranges in such a way that the make a constant electric field throughout the circuit, but my confusion is that how they arranges like that they makes the same potential in connecting wires of negligible resistance{which connects resistor with the terminals of the battery) as the terminal of the battery to which it is joined but in the resistor they don't makes the same potential everywhere why? how do they know it? and also isn't it very bizarre that they makes up the constant electric field everywhere? please guide me without involving complicated mathematics(if any required) and just try to give any logic behind this.

this image shows what I am thinking in my mind.

  • $\begingroup$ Not quite sure I understand what you are asking for. Before closing the circuit the electric potential will be equal in the entire circuit as there are no current flowing. The electric field around the circuit would be dependent on the actual layout of the circuit. I From what you are saying it sounds like you have "Idealized" to much for your question. You can look at the wire as resistors with very low resistance if that helps so there will be some electric field in the wires as well. but as you say they can be neglected compared to the resistor. $\endgroup$
    – Morten
    Commented Jun 30, 2021 at 8:39
  • 1
    $\begingroup$ do you know about surface charges in circuit? if yes ,then only u will be able to understand my question $\endgroup$ Commented Jun 30, 2021 at 10:27
  • $\begingroup$ Yes I do. That does not make your question any clearer, unfortunately. $\endgroup$
    – Morten
    Commented Jun 30, 2021 at 11:43
  • $\begingroup$ I am simply asking how does the surface charges know where to make what potential? for example, in the image, I have shown that they make the same potential as the terminal of the battery in the connecting wires of negligible resistance but in a resistor they don't makes the same potential everywhere . how does they know that this is a resistor and this isn't? and also why do they arrange to make constant electric field isn't it bizarre? $\endgroup$ Commented Jun 30, 2021 at 13:19

2 Answers 2


After initial transients, the total current in all parts of a circuit must be equal. If this condition is not met, the non-uniformity in the (E) field will shift the positions of charges until it is met. This is the same feedback mechanism that keeps the field equal to zero in a non-driven conductor.


Imagine you have a spring, said R, press it. You have an effect on R that now has a particular length. Now press the R spring with the help of... another spring ;) , said C (conductor), using the same energy you employed before: you obtain a different effect on R with another length (is longer than before because your energy is not "communicated" on R because is spent also on C that has is proper elasticity). If C (conductor) is a perfect translator of your energy it has to have no elasticity. So, there is a physical property that makes energy being translated from you to R: now please imagine elasticity is for a spring as the same thing resistance is for a conductor. Resistance is intended for the whole conductor in terms of his form, but there is a specific physical property linked to the material called "Electrical resistivity" that "tends" to be "0" in good and superconductors (resistivity equal 0 does not exist) and is responsible also for the behavior described in the answer edited by R.W. Bird (1). Electrical resistivity is a "microscopical" property.

(1) @MISC {648745, TITLE = {How surface charges in circuit knows where to make what potential?}, AUTHOR = {R.W. Bird (https://physics.stackexchange.com/users/238328/r-w-bird)}, HOWPUBLISHED = {Physics Stack Exchange}, NOTE = {URL:https://physics.stackexchange.com/q/648745 (version: 2021-06-30)}, EPRINT = {https://physics.stackexchange.com/q/648745}, URL = {https://physics.stackexchange.com/q/648745} }


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