Understanding basic electricity?

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so which of the 2 [ground and neutral] gets rid of the excess or overflow brought in by the live wire?

 

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I would have thought the circuit would trip if excessive power was delivered to circuit?

 

There shouldn't *be* any excess or overflow. Fault conditions like that would either cause a circuit-breaker to trip - or damage the devices connected.

This is why things like line-conditioners and surge suppressers exist.

Harry.

 

So does this mean essentially that BOTH the N and G wires do basically the same job and that job is to "divert" some of the electricity back into the earth?

 

No - the job of the neutral is to provide the return path to the power company. The job of earth is to act as a safety connection. There may be substantial current in the neutral wire, but it is a fault condition if there is *any* current in the earth wire.

On the latter point - this is what an "earth leakage trip" device is about. This is mandated if you feed your domestic supply to the outdoors - such as running a lawn-mower.

Harry.

 

Harry, let me break this down then one issue at a time please, "why" does the Neutral have to provide the return path back to the power company? If the idea is to bring power into your home, why send it back? Is this some sort of recyling issue or is this return neccesary to have electricity in the first place?

 

It is required by the very nature of electricity.

Electricty is a flow - and must go round a circuit. Think of a torch, with a battery, a switch and a bulb.

When the torch is switched on the current goes from the battery + terminal, through the closed switch, thhrough the bulb (making it light up) and back to the - terminal on the battery. The current makes a circuit - which is why we talk about electric circuits.

Mains electricity is not really very different. Instead of a battery there is a generator but that still has the two terminals (simplifying heavily), and the house light bulb also has two terminals. The current flows from the generator via the closed switch and through the light bulb and back to the generator.

Even 'static' electricity, the sort that produces lighning, does this, just not all at the same time. The cloud gradualy builds up a huge charge by a slow flow into it - untill the charge is so high that a spark happens, and the current rushes back to earth.

Harry.

 

One further point - I was talking about current - not power.

The circuit is required for the current to flow. As a result of the current flowing through the bulb it glows, and gives off energy.

So the flow of power is one way - from the generator to the bulb.

Harry.

 

Very nice! Now to Earth or Ground. What is the purpose of this?

 

As I said before - safety.

If, by some accident, the case of an appliance (such as a lawn mower) touches the live wire, that case would then be 'live'. Anyone touching it would provide a path from it to ground through their feet - i.e. they would get a nasty - perhaps fatal - electric shock.

If the case is already connected to ground then 1) the live wire would be shorted - blowing a fuse or tripping a circuit breaker and 2) anyone touching it wouldn't provide a better path to earth - so wouldn't get a shock.

Harry.

 

Just to be sure here, I know for a fact that you can touch a live wire or Neutral wire "separately" and don't get shocked BUT if you touch BOTH a Live and a Neutral wire that's binded together then you get shocked, I guess this expains the "circuit" principle for electricity to be present, am I correct?

 

This is very unlikely to be true if the live wire is 'live'. Unless you are wearing gloves, or have good insulation in your shoes you will probably get a shock. This is the principle behind the 'neon' screwdrivers - it allows a very small current through from the live wire to your hand, not enough to give you a shock but enough to light up the neon.

Neutral is nominaly at earth voltage - so won't give you a shock, or light up the neon.

If you were to apply power to such a short you would likely end up with either melted wire, a burned hand, and a blown fuse - or all three.

Do *not* attempt to do this!

Harry.

 

I don't understand, all through my life I have been changing wall sockets, installing ceiling fans, what I would do is simply follow whatever the exisiting wiring was to make the change so this is why I wished to know this now once and for all what each wire does.

Whenever replacing the wall socket or ceiling fan I would always deal with each wire separately as a friend of mine years ago told me that I will not get schocked by touching any of the wires as long as I don't touch both Ground and Neutral at the same time, how do you explain this? If this was hearsay, I would say then that this is wrong but since this is what I always do and don't get shocked, what gives?

 

Well first I would say that I wouldn't do such work without the fuse or circuit-breaker safely in my pocket. It is simply just too dangerous. Yes - I know some 'sparks' do - but it isn't safe.

Yes - it is safer to deal with one wire at a time, but accidents still can happen. Allways isolate a circuit before working on it.

And the comment about touching Ground and Neutral at the same time makes no sense - they should both be at 0V. However, I've seen some wiring where Neutral appeared to be live because there was a break between the wire I was dealing with and the house neutral, and the live side of the circuit wasn't isolated. In such cases the wire was effectively live via the load.

Harry.

 

I've seen many times where there would only be 2 wires connected to a circuit, does this mean that these has to be Live and Neutral or could it be Live and Ground? Since Ground provides a safety issue I have to assume that if you use only 2 wires then it has to be live and Neutral to get the electricity, correct?

 

Correct.

If it an appliance that only has two wires then the rule is that it has to be 'double insulated' to try and make up for the lack of an earth. This is usualy marked on the appliance with the symbol of a double box - one inside the other.

Harry.

 

So if you stumble upon an outlet in your house which only has 2 wires then you can always connect a Ground wire yourself, correct?

 

I do remember a potential differential coming into it, hence my original point and the question about flow.
Remember the capacitator experiment from school, where you have two charged plates close together and a current flows from one to another?
Then it gets complicated because the flow of electrons is the opposite to what you would expect. Being -ve charge, they move the wrong way...

Or something...

 

I'd want to treat an outlet with only two wires with great caution.

Harry.

 

Johnny, can you draw the path or flow of the electricity into the diagram?