Electronics > Beginners
How is Neutral Wire Neutral in Mains Electricity?
help_me_pick_username:
I am kind of confused about the Live and Neutral wires in Mains wiring. I've seen YouTube videos where someone touches the Neutral wire, but it doesn't shock them, but touching the Live wire does.
I'm going to try and explain my understanding of how Mains AC electricity works, please let me know where I am wrong. My understanding is that, if I simplify the AC waveform to simply a square wave instead of Sinosodial, 60Hz AC is where one wire is +240v and the other is ground 30 times a second, and for the other 30 times, this is flipped, so the other wire is +240v, and the other is ground. I know this is wrong, since you wouldn't be able to touch Neutral in this case, but where am I wrong?
tszaboo:
No. Phase has a sine wave on it. Like below. Sometimes positive, sometimes negative.
Neutral is 0V, constantly, normally conducting electricity.
Protetive earth is 0V as well, but it doesnt conduct normally electricity.
Dont touch any of these wires with bare hands, even if people like Eleoctroboom do this, it is extremely foolish. Buy a electricians glove, it costs like 3 dollars, and switch off the circuit breaker if you work on the wires.
help_me_pick_username:
It was never my intention to touch any of these wires, I was simply using that as an exmaple to explain my question.
I don't really understand how negative voltage works. I will have to do some more research on this.
When the Live wire is in it's negative state, doesn't that mean that Neutral is +240v relative to the Live wire? Sorry if these are stupid questions. I'm having some trouble wrapping my head around this.
magic:
Absolute electric potential is determined by excess or deficit of electric charge. It can be positive or negative. Earth is neither positively nor negatively charged so its potential is zero. Neutral is connected to earth so its potential is zero. You are neutrally charged too so nothing happens when you touch neutral, unless the installation is broken or you actually are statically charged and get a spark.
Live is alternately positive or negative. Neutral may be +240V relative to live when live is -240V, but it's still 0V relative to ground.
Now, if you isolate your floor from ground, connect it to live, stand barefoot on the floor and touch neutral, that's going to hurt :P
tszaboo:
Voltage is always relative. Meaning, that you always measure it between two points. It is that way by definition.
You take one point as the reference point, for example protective earth, place the black electrode of the multimeter on it, and measure it against it. So yes, if you swap the mutimeter wires, the polarity of the voltage changes. We just use a reference point, because then everyone understands what voltage we talk about.
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