explaining the purpose of neutral wire?

[ban-all-sheds]

The fact that Robert and I have the same surname might lead many to the correct conclusion that we are related, and you would be correct, Robert was my youngest Brother.

I know from conversations we had and from his e-mail folders that he had people on this forum who had known him for some time, and because of those who looked on Robert as a friend I thought that they would like to know that Robert is no longer with us. Unfortunately Robert was killed on Monday evening at work in a freak induction accident.

I know that some here may not be too concerned to know of this loss, I knew Robert for 200 Years and I know how difficult he could be, with all his talk of Tesla's work being more important than Faraday's, and his unerring belief that it was possible to derive 240,000 Volts from a 12V supply with only one winding, and his repeated fights with Jacques Daguerre about the properties of synthetic organic materials for camera bodies, but I am also aware of the other side of him, the side that some here saw.

I would like to thank those here who had become Robert's friends, I know he appreciated it and had the utmost respect for many members of this team, including Mickey, Minnie, and Felix.

He will be sadly missed.

 

[chris765]

I am also in my second year and this is a concept that I haven't quite got to grips with.
I understand that if you are stood at point 4 touching point 3 then there is no potential difference with the 0v. But say I were to connect a conductor at point 3 to an earth rod at point 4. Im guessing the resistance would be less than the return therefore sending the current through that.
So would I be right in saying that you wouldnt get a shock only if your resistance is greater than the neutral return path to the supplier?

In practice:
Say I were to touch the neutral terminal block in my CU with all the circuits on. I would get a shock because theres current flow, but yet thats been grounded to 0v because of the neutral return to supplyer. So although there is no potential difference between me and the neutral return, there is a potential difference between me and the line/load side of the circuit?

So am I to conclude that whenever a circuit is operating I would always get a shock if I were to touch the neutral side?

 

[chapeau]

the reason you don't feel it is that you are more or less on the same potential as the neutral as already explained not because the the electron is "knackered", try taking the neutral connection off the bulb and put your finger there and see how knackered your electron is!!

I suppose I pitched my explanation at the level which I understood the original poster to be at. Perhaps I got that wrong.

Now if you reread my post I mentioned push (force). work and energy. Energy, or a relative lack of it, was represented in my post as 'knackered'. If you consider what is happening to electrons in the circuit then using 'force, energy and work' provides a far better explanation than pressure of water in a pipe, and will survive scrutiny to a far higher level.

However I do agree that explaining it using pressure in a water pipe is sometimes all you need to do. Of course, I used electrons. Is the electron really at the switch waiting for it to be turned on, has it already moved from the switch to the bulb even though the switch is turned off, or is it in both places at the same time!!! So my explanation also falls short - eventually.....

To answer your question, you would get a just under 230v shock - though this would change as the wire in the bulb heated up.

I can see what you are trying to say chapeau

excellent, I shall consider my post a success, though am far more interested if the original poster found it useful

but as Goldburg has already said"A voltage does not flow through the circuit. Current flows, not voltage"

I am aware of this, but I don't think it is particularly relevent to the question, which was primarily about volts.

I consider your criticism to be objective. Cheers.

 

[Goldberg]

I'm open-mouthed to see the sheer number of words that people are writing about something so simple.

If you connect two points that have a potential difference, then current will flow. Nominally it will flow 'from' the point that has the positive potential (although in terms of electron flow the situation is different).

If you don't connect the two points, then no current will flow.

And why all this talk of the relationship between neutral and earth? It's a meaningless distraction.

If anyone thinks that discussion of the earth is relevant or essential, then please explain the function of the neutral path in the output from a generator.

 

[matt1e]

I understand that if you are stood at point 4 touching point 3 then there is no potential difference with the 0v. But say I were to connect a conductor at point 3 to an earth rod at point 4. Im guessing the resistance would be less than the return therefore sending the current through that.

it would not be less in a healthy system as the path through earth will always have more resistance than the return through the neutral conducter

In practice:
Say I were to touch the neutral terminal block in my CU with all the circuits on. I would get a shock because theres current flow, but yet thats been grounded to 0v because of the neutral return to supplyer. So although there is no potential difference between me and the neutral return, there is a potential difference between me and the line/load side of the circuit?

you have to have potential difference for current to flow and potential difference is measured in volts the PD between neutral and line is still there but because neutral is also connected to earth there exists no or very little PD between them hence 0v
ie neutral is only 0v in reference to earth
therefore if there is no potential difference between you and neutral then no current will flow its the same reason birds can sit quite happily on overhead lines,they dont get electrocuted because they are at the same potential as cable they are sitting on

So am I to conclude that whenever a circuit is operating I would always get a shock if I were to touch the neutral side?

no but not recommended as a neutral fault can cause the answer to be yes
matt

 

[chapeau]

The problem is, goldberg, the original poster doesn't think it's simple.

Most, if not all, the other posters on this thread 'get it', the original poster doesn't. A bit like when we first got in a car to drive, bloody hell, what a nightmare, now we do it in our sleep, sometimes literally!

So this is really an exercise in

1) Reading the question
2) Understanding the question
3) Answering the question in terms that the orginial poster understands.

NOT

Understanding the subject matter.

Some, if not most, of the answers have failed abysmally to satisfy 1,2,3 (or even one of them).

Some people are good electricians but ****e teachers, some are bad at both, we are looking for the ones who are good at both!

 

[Space cat]

So would I be right in saying that you wouldnt get a shock only if your resistance is greater than the neutral return path to the supplier?

You've missed the point of the drawing. In order to get a shock, a significant CURRENT must flow through your body. That current will be equal to the VOLTAGE across your body divided by your RESISTANCE. That's Ohm's law.

Now look at the drawing. Almost all of the resistance in that circuit is in the load (2) with very little in the wires. The current can be calculated by dividing the voltage by the total resistance. Now use Ohm's law in reverse, ie voltage = current x resistance, to find the voltage across each circuit element: the live wire, the load and the neutral wire. The resistance of the wires is (or should be) very low compared to that of the load and so only small voltages appear across them. That's the way you want it because voltage lost in wires is wasted. This means that the voltage between point 3 and earth (4) is small. If you touch point (3), this small voltage is the only thing trying to push current through your body and so you don't get a shock but --

If you break the neutral connection between (3) and (4), there will be no current in the load. Now redraw the circuit but with your body as the return path to earth. This is a paper exercise; don't try it! Your own resistance will now be the highest in the circuit. What does Ohm's law tell you about the voltage at point (3) now.

 

[matt1e]

I'm open-mouthed to see the sheer number of words that people are writing about something so simple.

because I for one has been up all night and was bored with the tv

And why all this talk of the relationship between neutral and earth? It's a meaningless distraction.

because the op asked

why does it have 0 volts?

matt

 

[Goldberg]

The problem is, goldberg, the original poster doesn't think it's simple.

Quite so, but he's wrong.

Most, if not all, the other posters on this thread 'get it', the original poster doesn't.

I really think that a lot of them don't.

A bit like when we first got in a car to drive, bloody hell, what a nightmare, now we do it in our sleep, sometimes literally!

Really? I find that I drive best when fully concentrating on it, and I repeatedly revisit the first principles of driving in an effort to avoid developing bad habits.

Some, if not most, of the answers have failed abysmally to satisfy 1,2,3 (or even one of them).

Yes. Those people should stop adding confusion and just butt out.

Some people are good electricians but s***te teachers, some are bad at both, we are looking for the ones who are good at both!

Seeking understanding on a forum like this is like expecting one lone student to flourish in a classroom full of teachers.

And if someone in their second year of studying hasn't already "got" what the neutral is, they should be barred from the building until they do, because it's completely impossible for them to be safe without that understanding.

 

[Goldberg]

And why all this talk of the relationship between neutral and earth? It's a meaningless distraction.

because the op asked

why does it have 0 volts?

Indeed he did, but the answer has nothing to do with earthing. Or an earth. Or the Earth.

If you, or anyone, thinks that it does, then please explain the function of the neutral (or 'minus') connection in a circuit comprising a battery, a lamp, and two wires, all sitting on a rubber mat.

 

[matt1e]

A battery hasn't got a neutral but if you insist
assuming the battery is charged and the lamp ok and connected to the battery then the minus connection will provide a path for electrons to flow back to the positive via the lamp filament

now please explain to me and the op why there is 0v on the neutral as I have obviously been wrong in my assumptions so need to be corrected
so go on please enlighten us oh knowledgeable one
pretty please

matt

 

[matt1e]

pretty pretty please
with a cherry on top

 

[RF Lighting]

Batteries run on DC, and have a positive and a negative.

Mains wiring is AC, and has a live and neutral.

These are both completely different.

There is 0V on the neutral because it is tied to earth. This means that the neutral wire is physically connected into the ground with the use of earth rods and the like on he distribution network, and therefore, if you take a voltage reading between a neutral wire and earth, it shows 0V.

 

[Goldberg]

There is 0V on the neutral because it is tied to earth. This means that the neutral wire is physically connected into the ground with the use of earth rods and the like on he distribution network, and therefore, if you take a voltage reading between a neutral wire and earth, it shows 0V.

So if you don't use 'mains' or a 'distribution network', and instead use a generator, and don't connect an earth to anything or connect anything to an earth, what is the purpose of the neutral connection?

Does it have a different purpose to the neutral in a 'mains' installation?

 

[hellmooth]

wow thanks for all the information,much appreciated and helped clear it up somewhat

so when the current has been used by the load and returns through the neutral wire,finally being connected to earth back at substation,it is for want of a better word dissipated into the ground?it still has the same current going through it but the voltage is at near zero as its not being pushed with the same intensity?