Thanks mik3, I think I get it now. So the neutral wire is safe simply because it is grounded, not because it isn't connected to the main power supply.

If that's the case, then is the neutral wire neutral only for safety reasons? Is there any other purpose for grounding one of the hot wires from the generator?

 

I am still confused about the ac. I am wondering if I am correct in the bottom reasoning. Any help would be great.

How can the black wire itself osscilate current? I don't think their is any current flowing thru the black wire until the circuit is complete.

ignore the . dots they are just for spacing stuff out in picture

power company circuit----------------------
|..........................................................|
powerlines-------------------------------- (has ac because complete)
|
|
|(main black house line )
|(no ac until the circuit is complete)
|
house

I would think both the white and black are hot once the circuit is complete. Because current is flowing back and forth from ground white wire to black powerline wire.

And the only reason why they call black the hot wire is because this is the wire that produces the alternating current from the power company when the circuit is complete.

Also with my digital mulitmeter I found that the left prong in the outlet is the white neutral ground wire and the left is the hot black wire.

Also since it was a 3 prong outlet the bottom was green ground wire.
And if you use the multimeter on both right and bottom prongs you get 0 volts as should be since they are both ground and have the same electical potiential. But connected left to either bottom or right gives 120 volts as should be.

So in theory if you held the green and white wires while power was on you won't get shocked. It is only when you hold the black wire and complete the circuit that screws you.

But what if you never completed the circuit while holding the black hot wire. Say you could float in air would their still be a completed circuit somewhere that I am missing. Because without a completed circuit their will be no voltage. It will be an open circuit.

curious about what would happen but not stupid enough to try it

 

If that's the case, then is the neutral wire neutral only for safety reasons? Is there any other purpose for grounding one of the hot wires from the generator?

Personally, I don't see any other reasons for doing it. Also, they do it as high voltages not to be developed on the system due to static electricity (safety reason again).

Have a look here:

http://www.allaboutcircuits.com/vol_1/chpt_3/3.html

 

Looking at that chapter I am wondering what would happen if you connected the black hot wire directly to the earth.

I am assuming that the resistance from the 10 gage copper wire won't be enough to keep the current under 200Amps and the main circuit breaker would flip open. And the whole house would lose power.

And if their wasn't a main circuit 200Amps switch then it would blow something at the powerline or street box? Assumeing their wasn't a 200amp circuit main breaker in the house. But ofcourse this would probably be a saftey volation anyway.

just curious not like I am actually going to take out the main breaker anyway or do any of this.

 

I think I'm semi-safe to say that if you grounded the hot wire to the earth, you'd trip the main breaker if you were lucky. The main ground goes there, anyway. If that didn't do anything, the wiring would melt in the wall and probably cause a fire. In theory, this would work (putting hot to earth rather than the actual ground for the circuit).

It should be said that all grounds need to go to 1 spot in a home at their final termination (very much like star grounding in amps, etc). If multiple grounding points are used, the ground reference can be somewhat 'floating', and result in breakers NOT tripping! This is because of resistance between multiple grounding points. Here in the US, this is typically done at the water main (old style, unreliable nowadays) or to a single grounding rod (best way).

Picture household power as using 2 ends of a center-tapped transformer. Now you can see why the black wire is the hot wire, and you get 2 circuits out of a 240VAC line:

240 ------------- >> hot 120V
CT--------- GND (neutral and safety ground)
240 --------------->> hot 120V

The 240V line for stoves, dryers, etc. goes across this connection allowing for the higher voltage.

 

Looking at that chapter I am wondering what would happen if you connected the black hot wire directly to the earth.

I am assuming that the resistance from the 10 gage copper wire won't be enough to keep the current under 200Amps and the main circuit breaker would flip open. And the whole house would lose power.

Yes. Whether the breaker would trip before vaporized metal exploded outward is another question. This is why electricians take extreme precautions (special jackets and face-masks) when working on live panels.

And if their wasn't a main circuit 200Amps switch then it would blow something at the powerline or street box?

Yes. There are also even larger overcurrent protection devices even further upstream.