# How does current flow in a short circuit? [duplicate]

In a short circuit, the potential difference across the terminals of a battery (consider a single cell with internal resistance)is 0 according to the equation $$V=E-Ir,$$ where $$r$$ is internal resistance of the cell,$$E$$ is the emf of the cell and $$V$$ is a potential difference across the battery.

If the potential difference across any two points in a circuit is 0, the electric current $$I$$ doesn't flow right? Then how does current flow in a short circuit (assume 0 resistance for short-circuited wire)?

## marked as duplicate by John Rennie, ZeroTheHero, Kyle Kanos, GiorgioP, Jon CusterFeb 28 at 4:22

• Please don't write in all capitals, as that's the equivalent of yelling. Further, you should come up with more descriptive title so that other users can know what you're asking. – Kyle Kanos Feb 27 at 11:20
• Forget the word, "short." It may be useful to talk about a "short circuit" when you are trying to describe a fault condition in some electrical system, but that phrase is not useful when you're analyzing a circuit. It's just a circuit. The circuit that you have described (a practial battery whose terminals are directly connected) can be modeled as an ideal voltage source in parallel with the battery's internal resistance. Now, try asking why current flows... – Solomon Slow Feb 27 at 14:00
• ...But that's an electrical engineering question. If you want to ask a physics question, try asking this: How is it possible for current to flow in a length of superconducting wire when the voltage difference between the two ends of the wire is zero? – Solomon Slow Feb 27 at 14:01

Think about a conventional (idealized) circuit with an ideal voltage source driving current through a resistor. I am sure you agree that current $$I = \frac{U}{R}$$ will flow.

Now take any two points between resistor and voltage source. The voltage drop between them is zero (in practice), but still a current flows!

This means, you will always find pairs of points in a typical circuit with current flow made of resistors and very low resistance wires, between which the resistance (e.g. of the cables) is negligibly small, and therefore the voltage drop in the presence of current flow is essentially zero.

• probably, the best explanation, thnx :) – PranshuKhandal Feb 28 at 18:25

If there can be no current between two points where the potential difference is zero, then there can be no current flowing in ideal wires (wires with zero resistance) that connect together voltage sources and circuit elements that do have impedance. Obviously, that is not the case.

Hope this helps.