Is the potential at each point on a circuit same,if so why? I have read that in order for current to flow through any kind of resistance,the potential of charges reaching resistance is higher than those exiting it. ie. all the charges before it are at same potential and the charges exiting it are at some low but same potential.this means that there are only two potential levels in a circuit. for better understanding of my doubt please check out this video https://youtu.be/-Rb9guSEeVE


Kirchoff's law says that $\Delta V_{\rm loop} = 0$, i.e. that the voltage summed around the closed circuit must add to zero.

If you have a circuit with one battery and one resistive element, like a resistor or a lightbulb, like this:

enter image description here

Circuits are typically modeled with ideal wires, which have no resistance. That means that in this situation, if the battery is 3V, then every point in the wire between the (+) terminal of the battery and the "upper" terminal of the resistor is 3V. At the resistor, you see a voltage drop of -3V. Then, from the bottom of the resistor back to the (-) terminal of the battery, every point is 0 volts. So in this very simple circuit, the wires are held at two distinct potentials.

In reality, wires do have resistance and dissipate energy through heat, but this is very small, so it is a good approximation in many applications to model the circuits with ideal wires.

  • $\begingroup$ Can I conclude that at each point the potential changes in real life circuits $\endgroup$ – user265825 May 28 '20 at 14:35
  • $\begingroup$ Yes, but only by a very small amount. $\endgroup$ – zhutchens1 May 28 '20 at 14:40
  • $\begingroup$ Now if the potential changes even with small amount..then as I go from positive terminal of battery to starting end of resistance,then the potential would have changed significantly, isn't?? $\endgroup$ – user265825 May 28 '20 at 14:46
  • $\begingroup$ No, when I said a very small amount, I meant a very small change in potential from the terminal of the battery to the starting end of the resistor. For most practical purposes, consider the potential across the wire to be constant. In reality it is never really more than 2-5% I believe. $\endgroup$ – zhutchens1 May 28 '20 at 14:48
  • 1
    $\begingroup$ There are circuits where the resistance of the wire matters and must be modeled, but they tend to be rare. You find them in "power circuits," that are moving large numbers of watts through low resistance loads. For a point of reference, 18ga wire typically has a resistance of about 6 ohm per 1000ft. In most "reasonable" circuits, this loss is far less than the uncertainty you have about the resistor's actual resistance, and lots of other fun fiddly details, like how the resistance of the resistor changes with temperature. $\endgroup$ – Cort Ammon May 28 '20 at 14:55

Not the answer you're looking for? Browse other questions tagged or ask your own question.