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How Exactly Does Earthing Work?

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i'm totally confused...
I've heard that CRT has very large voltages inside...( more than Mains)
Would it be causing that?

Usually around 25,000V - it's 'caused' by a transformer.

It'll cause me a severe tingle every time i touch USB/Screen... So what would you say?
I'm also sure that my multimeter is TRUE...

I would say a slight tingle, assuming there's no fault of course - and the slight tingle is within permitted limits - after all the units have to pass strict safety standards (at least in the UK).

Why don't you just ground it? - or is the problem that the unit is grounded, and you're statically charged, and discharging every time you touch it?.
 
Can someone explain to me how screwdriver voltage tester works?
Here's the thing:

The little light is on even if I jump (on a wooden floor) but if I put big metal
pipe on the floor and make it touch (without me touching anything) the screwdriver
the lite is NOT on. ???


Edit:
I think it's about the body surface and what capacitance it forms
with the earth. (So your body is like an antenna.)
 
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What is the requirement of neutral wire? why cant we use Earth as(instead of) Neutral wire?

EDIT: Hence, decreasing the length of wire used and also making wiring more economical!
 
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The neutral is where return current that powers the appliance actually flows back to the power plant. We get lazy and call this "ground" in our circuit boards. The actual earth/ground is connected to the ground where the plug is and no current is supposed to flow through it in normal operation.

It's cheaper to only have the neutral, but the ground wire isn't that expensive since it isn't very long because it's connected nearby to the ground where the plug is. It doesn't run all the way back to the power plant. But it's not as safe since the other end of the neutral is at the earth/ground potential of the power plant. This is not necessarily the ground/earth potential of the ground you are standing on where the plug is, and is therefore not necessarily the ground potential you are at. THat makes it a potential shock hazard.

And even if the earth/ground potential at the power plant and where you are is the same, current flowing through the neutral means that your end of the neutral wire might be dangerously above or below earth/ground potential which is also a shock hazard.
 
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And even if the earth/ground potential at the power plant and where you are is the same, current flowing through the neutral means that your end of the neutral wire might be dangerously above or below earth/ground potential which is also a shock hazard.

Not sure where in the world you are, but here in Australia (and many other parts of the world) we have what is known as the "MEN" system - Multiple Earth/Neutral.

Each connection point to the grid (house, office, remote pump, whatever) is required to have its own local earth. This is usually an appropriate sized ground stake and/or good bond to the water pipes.

The grid "Neutral" and the local "Earth" are bonded at a single point in the switchboard. That's the ONLY place the earth and neutral are bonded for that site. (This is important later).

The grid "Neutral" actually carries virtually no current at all, and certainly does NOT connect all the way back to the power station (not here anyway). Power is distributed as 3-phase, where the 3 phases are electrically 120 degrees to each other. Given enough loads (thousands of houses), connected from one phase to the "star" point ("Neutral", the loads all balance each other and the only current in the neutral is any fault or "out of balance" current. Usually very small.

Back at the house, by tying (bonding) the earth and neutral, you prevent your local neutral from having a major potential difference to all your "grounded" household parts (exposed metal in your sink or bath, for example). The single earth bond also lets you use "RCD" (Residal Current Detectors, or "core balance" or "Earth Leakage Circuit Breakers" - all basically the same thing) actually monitor your power circuit for faults. If power flows through the active, but NOT back through the neutral, the difference is flowing somewhere via "ground" - like someone throws the toaster in the bath with you - and very quickly disconnects the power, hopefully saving your life.
 
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There are two pins on every outlet (power-point). It does not mater what we call them.
We now connect a toaster to the power point. A toaster has a metal chassis.
Suppose the element inside the toaster touches the outside metal case.
Suppose you touch the metal case and a metal object such as the sink. You will get a shock if the active line touches the metal case.
You will not get a shock if the neutral line touches the case.
This will depend on how the plug is wired and sometimes a plug is wired around the wrong way.
To prevent this situation from occurring, we add a third wire or pin to the power-point and call it earth.
This wire goes to a pole in the ground near the front of your house and also the waterpipe coming into the house.
If the element touches the metal case the fuse will blow if the active line touches the case but nothing will happen if the Neutral touches the case. In both cases you will not get a shock.
As you can see, the reason why "earth" or "earthing" was introduced, was due to people wiring plugs and sockets around the wrong way.
In the old days, if you got a shock when you picked up the kettle, you just plugged it into the wall around the other way.
But when electricity went to Europe with 240v, a shock like this would throw you across the room and so earth protection was needed.
Earth is generated at the house and provides a cage around all electrical appliances to prevent the user getting a shock.
 
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we can't earth the Grid neutral at the user premises. it is grounded only at the 11KV to 230/440 transformer point.
later as we see from the distant user point, the wire would have some drop. If we try to ground the neutral there, the potential difference, however small, would draw enough current, as the said drop is of low impedance.
 
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