Paulo, please note carefully that at the point where your supply comes from(usually a big transformer on a pole or substation) one side of the supply is connected to very solidly connected to earth. This forms the reference point. Now two wires are run to you house(or domicile).
one wire is called the "neutral" because it is connected to side connected to earth. That makes the other wire "hot" or "live" with respect to the "neutral" or any earth point. Note I refer to our distribution system on Down Under.
Regarding measuring the volts 5000km away I would suspect that there would be so much stray currents from a lot of sources the result would be meaningless unless you could switch off all other supplies and control any self generated currents in the soil.

Prof Buxton, let me please explain what I mean by 5000mile away ground. What I mean is not that any point 5000 mile away can be used to ground the neutral. What I meant is whether AFTER grounding the neutral at a point on the earth, if you can use Any Other points on the earth whatever (by sticking one of your multimeter ends deep into pure Soil), (disregarding astray currents and voltages), to measure voltages along your circuit. You explained to me previously that this can be done because the earth is just like a big metal piece..... Is this correct ? This is really my most important question and the big issue that I've had all along...

 

Dirt and dirt 1000 feet away may not be at the same potential. For the most part it is. In the details it isn't.
The "dirt" we are talking about is also about 7 to 20 feet deep which is different than surface dirt. There's the "water table" to consider too. Modeling it as a big chunk of metal may work at this level and it's OK to accept that model.

The potential difference across the Earth's surface particularly varies during thunder storms.

Where this becomes important is the grounding of swimming pools and walkways.

 

I think what the OP is saying is could drive a ground and get a reading. He could if the voltage is high enough to overcome the resistance of the wire 5000 is 16,000 kohms that rounded off but good enough to get a idea. But if its step down to house voltage and grounded at transfomer
A ground drove in the ground should read voltage of the hot wire.

 

Paulo,I understood what you meant. Maybe I wasn't clear. Ideally yes, you could measure that voltage in the
way you describe. That is treating the earth as a large conductor. However, realistically, due to the makeup of the real earth and stray currents , natural or man made, if would be difficult to distinguish your voltage from background noise. Maybe if the voltage was very high it may work or of a particular frequency. After all radio waves use the earth as a "ground plane", buts that's a different story.

 

Paulo,I understood what you meant. Maybe I wasn't clear. Ideally yes, you could measure that voltage in the
way you describe. That is treating the earth as a large conductor. However, realistically, due to the makeup of the real earth and stray currents , natural or man made, if would be difficult to distinguish your voltage from background noise. Maybe if the voltage was very high it may work or of a particular frequency. After all radio waves use the earth as a "ground plane", buts that's a different story.

Prof Buxton, I can totally agree with what you say about extra noise, but I being a very abstract person, and when trying to understand things I first idealize everything and then go into the practical side of it, still would like to confirm that the fact that you can actually do this, is because the neutral wire is also grounded, and therefore the earth (as it is currently chemically made up ) would really act as a big relatively good conductor (for high relatively voltages), and therefore you could say that a point miles away is identical to the actual neutral wire when measuring voltages from.

I would like to do this experiment at home, to go out in my garden and stick a copper rod into the soil, and then use my voltmeter and measure the voltage between this rod and the hot wire. Will I get the actual voltage or will I get 0 ?

 

Your meter needs only a tiny current to "see" a voltage, so I predict it will work fine. But if you wanted to use, say, a 100w lightbulb as your meter, I'm less sure how far away you could get. Interesting experiment. I guess from what we've heard, it should work for a surprisingly long distance.

 

I would like to do this experiment at home, to go out in my garden and stick a copper rod into the soil, and then use my voltmeter and measure the voltage between this rod and the hot wire. Will I get the actual voltage or will I get 0 ?

The Ground is still Ground as a Reference to Voltage. I can testify this to be true when I was working on a dishwasher and was to lazy to go back to my truck and get my Meter, e.g. I knew what the problem was before entering the home.

The homeowner was not there and I was by myself, little did I know the homeowner switched Hot and Neutral. The Door Latch switch could have saved me, but in this case the Hot AC came in on the Neutral Leg, so when I touch the back of my wrist on the Copper Pipe feeding water supply to the dishwasher and then grabbed the wire of the bad Water Valve my eyes rolled back into my head and I passed out. Luckily I let the wire go or I wouldn't be able to tell this story.

So, yes. You will have Voltage and Yes, the ground is the reference. Don't believe otherwise or you'll be dead.

kv

 

I would like to do this experiment at home, to go out in my garden and stick a copper rod into the soil, and then use my voltmeter and measure the voltage between this rod and the hot wire. Will I get the actual voltage or will I get 0 ?

Here you go.

Max.

 

Lol here a live video I made for the op

As you can see you can just stick a screwdriver in the ground and read volts
Don't do this at home if you don't know what your doing it can kill you

 

Lol here a live video I made for the op

As you can see you can just stick a screwdriver in the ground and read volts
Don't do this at home if you don't know what your doing it can kill you

Lol ! That's great you are very kind. I have actually just done the experiment myself, and I was really surprised and happy! I never thought such thing would happen !! Amazing and very cool! I am loving all this stuff Thanks guys !!

 

Here you go.

Max.

Going to watch it now Thank you Max and best wishes.

 

In your OP, you mention just getting into electronics, there is a lot in between starting the subject and what you have been trying to grasp here.
I would strongly recommend you find a course or material that explains AC & DC theory before going any further.
Max.

 

In your OP, you mention just getting into electronics, there is a lot in between starting the subject and what you have been trying to grasp here.
I would strongly recommend you find a course or material that explains AC & DC theory before going any further.
Max.

What do you mean? I have only tried to understand voltage... isn't that the beginning? Thanks a lot. I have around 7 books so far and strangely none of them explained any of this hence why I came here. I will keep studying. Best wishes