Continuity...How does it work?

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  #1  
Old 12-25-00, 04:59 PM
G
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When I used a voltage tester between a black and ground wire contained within a light switch, the voltage tester light came on. I don't understand why. Given that all the ground wires in my home are connected to a rod driven into the ground outside of my home, I just don't see how this creates continuity. Electricity is just looking for a path to continue on, right? What happens if a person grabs only the "hot" black wire without touching the ground wire?

Can someone please elaborate? If I've botched the terminology, please feel free to correct. I'm just trying to get a real understanding of how eletricity works and how wiring within the home works. If you have any book suggestions for the novice, please mention that too.

Thanks.
 
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  #2  
Old 12-25-00, 06:07 PM
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Ed,

As we discussed in your other post, you are not testing continuity. Your tester is testing for voltage.

Q: What happens if a person grabs only the "hot" black wire without touching the ground wire?
A: Well, perhaps nothing if you're not well grounded or your skin resistance is high. But in general, you're dead!


Q: Given that all the ground wires in my home are connected to a rod driven into the ground outside of my home, I just don't see how this creates continuity.
A: You are referring to "completing a circuit". The ground is a perfectly acceptable place for the higher voltage to return to a lower potential. The ground itself completes the circuit, since the power company generated this voltage relative to ground in the first place. (I realize that this may seem like a bunch of mumbo jumbo to you, but I'm struggling to find a good way to say it -- all ground, whether the ground itself or the grounding wire is at approximately the same potential).

Q: Electricity is just looking for a path to continue on, right?
A: Right. And through your heart on its way to your feet and then to ground is a perfect path. It only takes a few milliamps to kill you.

Q: If you have any book suggestions for the novice, please mention that too.
A: Chance are your local public library has many books that will give you the understanding you seek. Just look up home wiring. If you want more, sign up for an introductory class in circuit theory at your closest college.
 
  #3  
Old 12-26-00, 05:21 PM
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Electricity is an infinite entity. There are unlimited catogories of electricity and how it is used.

On the subject of house wiring. You have a transformer that is fed by alternating current. This means that the flow of electricity flows in oppisite directions in apporximately a period of time of 1/60th of a second. This alternating current gives us a chance to raise and lower the voltage at will. This transroming of a voltage level is not possible in a direct current style circuit that flows only one direction.

The transformer outside you house and owned by the power company provides two hot lines and one grounded llne. The two hot lines are appoximtaly 180 degrees out of sinc with each other. IN generic terms line one is pulling while line two is pushing. Then 1/60th of a second later line one will reverse and push instead of pull and line two will pull instead of push.

The neutral or ground used as the return path is not a path to earth under normal usage. The neutral is a path back to the center tap of the transformer which is the source of the power that the neutral is returning the path from. The center tap of a transformer is point "0". This is half way between line one and line to in a picture of a sine wave.
This is why this ground is called a neutral. It neither pulls nor pushes compared to the two hot lines that are pulling and pushing. Kind of like to men of equal strength pulling on a rope in oppisite directions. Neither gains because the pull is equal in both directions. Now if a man stood in the middle and grabbed the rope this man would be a part of the force of pull in both directions but where he grabbed the rope is on neutral ground of the force neither pulling nor pushing.

An equipment grounding path is the ground that you spoke of that is connected to earth. This path is only energized when their is a fault or leakage to earth. The connection to earth that you speak of can give you a weak current flow but is unreliable to operate a piece of equipment with. This path to ground is for emergency use only in order to give the electricity an easier path to earth than your body. Thus attempting to protect you from being killed from a leakage to earth through your body. Electricity will take its easiest path and the resistance in your body is much more resisant to the flow of current than that bare wire connected to earth. Therefore the most of the electricity will hopefully go down the wire instead of you body to leak to earth.

For electricity to flow the circuit must leave the transformer and come back to the transformer. This however does not mean that a completed circuit must have a path back to the zero tap level of the transfromer 'neutral'. Line one and line two also can produce work. Actually electricity throughout the electrical world would not need a neutral at all to operate in doing work if all electrical circuits were a balanced load.

The path to earth that you speak of is not your return path, the path back to the transformer's center tap is you grounded path or neutral. The path to earth is only an emergency escape route in case of electricity leaking from a completed circuit's path.

Hope this helps

Wg

 
  #4  
Old 12-27-00, 07:25 AM
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Wow. Great reply! It's terrific to see knowledgeable folks like yourselves in this forum. More information than I can shake a stick at!

Thanks again.

Ed
 
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