# How does neutral in single phase AC work?

How does neutral in a normal one-phase outlet work? I looked on the internet and I know it carries the current back to the source, but does it do that in the inverse of the phase or does it provide no voltage at all?

simulate this circuit – Schematic created using CircuitLab

Figure 1. Left: AC supply without earth connection. Right: AC supply with earth connection.

The circuit on the left is floating with respect to ground. Current that goes out on one line returns on the other. If you were to clamp an AC ammeter around the two wires it would read 0 A because the feed and return would cancel each other out.

The circuit on the right is identical except that the lower wire has been "neutralised" by connecting it to earth. That means that the voltage on that line should stay very low - rising to a couple of volts if there is high current running through it.

Again the sum of currents will be zero.

How does neutral in an normal one-phase outlet work? I know it carries the current back to the source. But does it do that in the inverse of the phase

For low frequencies and circuit lengths that are well-below wavelength distances, the current that flows in the neutral line is in-phase with the current that flows in the live line (in that the two currents rise and fall together).

However, because the live and neutral wires are usually quite close physically, you can regard the live current and neutral current as in opposition to each other because they travel in opposing directions.

does it provide no voltage at all?

All conductors drop voltage when there is load current so, there may appear to be a small voltage on the neutral wire relative to true ground/earth.