I want to know the basic difference between live & neutral wires and positive & negative wires(connected to a battery), or if they are the same but the names are different.


2 Answers 2


Here's a somewhat simple way of looking at it;

All circuits, whether DC (battery) or AC (household mains) require a flow of electricity around a loop (preferably including a load otherwise its a short circuit). So the power source will have 2 wires, current flows out of one, round the circuit, through the load, and back to the power source via the other wire. For a DC supply the convention is to call one + and the other - . Current is the flow of electrons. They move from the - to the + (electrons are negatively charged so anything positive will attract them).

For an AC supply there is no + or - because it changes directions e.g. 50Hz AC changes 50 times a second, that's why its called "Alternating Current". But you still need the loop, the circuit, hence 2 wires live and neutral. For me (UK) it's 230V nominal a.c voltage on household mains. That's the voltage between the live and the neutral. For reasons of safety one side of the supply is held at (or exceptionally near to) the potential of the earth. It we didn't tie it down you could have, with respect to earth, say, 1230V on the live and 1000V on the neutral,still 230V on the circuit so everything works the same BUT exceedingly dangerous if you touch either conductor and very demanding on the insulation to stop current leaking to earth, the metal of your cooker or your fingers on the light switch. So we tie it down, one end of the ac supply is "earthed" (somewhere in the supply system) and by convention the wire which is the earthed end is called the neutral.

Now when everything is working properly in an AC household circuit the current is confined to the correct wires and for each load/circuit the current through the live is equal to that going back through the neutral and none "leaks" away. In the case of a fault or accident some of the current may leak away to earth and not travel through the neutral wire. There is a difference between the live wire current and the neutral wire current and that is what trips your RCD/RCCD.


I assume "live and neutral" refers to the alternating current (AC) home installation?

That is very different from "positive and negative" in a battery, which is direct current (DC): the two poles of the battery have different potential, with a (more or less) constant potental difference (voltage) of, for example, 1.2V; one pole is the "positive" one, the other the "negative".

In the AC system in your home, the two connectors (ignoring possible ground connector) of a wall plug do not have constant potential difference (voltage), the voltage changes very quickly (around 50 times per second) between positive and negative (with a maximum of around 110 of 220 Volts, depending on where you live), in a kind of sinus wave. However, one of the connectors (called "neutral") will usually have very, very similar potential to "the ground", i.e., mor or less everything else around you.

Remark: there is usually still a tiny potential difference to ground: if you connect neutral and the ground connector of the wall plug, then in a decent installation the RCD "protection switch" should immediately switch off (as it detects a small current.

PS: Please do not fool around with the electric installation if you do not know very well what you are doing (in particular, do not shortcut ground and neutral to test the RCD); you can get yourself killed. Also, I assume "live" wire cal also mean something entirely different (such as a wire that is connected to a power source, as opposed to a disconnected one), you would have to provide context.

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    $\begingroup$ There is no "around" 50 times per second; the line frequency is very tightly controlled. So you get 50 Hz or 60 Hz or whatever your local electricity grid uses, but you get that to a pretty large number of significant digits. Someone on Electrical Engineering can probably elaborate on exactly how many significant digits. The RMS voltage varies far more than the line frequency, and even that is reasonably tightly controlled. $\endgroup$
    – user
    Mar 21, 2017 at 9:53
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    $\begingroup$ The two connectors (ignoring the ground one, of course) change their voltages between positive and negative, fine, but that means the "live" wire will have positive and negative voltages (periodically) and electricity comes to our homes through the live wire but the current flows from positive to negative potential so, how can electricity reach our homes? $\endgroup$
    – Adik001
    Mar 21, 2017 at 11:06
  • $\begingroup$ The "neutral" wire will have (approximately) zero Voltage with respect to the "ground". The "live" wire will have positive and negative voltages (periodically) with respect to the neutral (and therefore with respect to ground as well). The current will flow from neutral to live (through your electrical appliance, thus providing energy) for some period of time, and then change direction and flow the other way. $\endgroup$
    – Jakob
    Mar 22, 2017 at 10:40

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