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#50705 - 04/10/05 10:15 PM Volts, Amps, & Ohms
aldav53 Offline
Member

Registered: 08/22/01
Posts: 547
Loc: Chandler, AZ USA
Over the years I have come across a lot of electricians that do not understand the relationship between V, A, & Resistence. I would say you can touch a recepticle in a home or go out and touch one side of the main feeder lug in the panel and it would be the same (standing on the same surface of course) because even though the main lug is capable of putting out more amperage, you are not going to draw it, as long as the resistence in your body is the same for both. Basically.. the only way to draw more current is to either raise the voltage or lower the resistence. Simple concept but many even experiened electricians do not understand this.
Has anyone come across this?
:-)
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#50706 - 04/10/05 11:50 PM Re: Volts, Amps, & Ohms
e57 Offline
Member

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
Have to re-remind myself all the time.
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#50707 - 04/11/05 07:46 PM Re: Volts, Amps, & Ohms
Gregtaylor Offline
Member

Registered: 03/02/05
Posts: 212
Loc: Boise, Idaho, USA
Yeah, when I have to climb up on a roof and cut the POCO service lateral for a srvice change or damage repair, I have to remind myself too. I understand it perfectly, but it doesn't make my spine any stiffer.

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#50708 - 04/11/05 08:49 PM Re: Volts, Amps, & Ohms
Celtic Offline
Member

Registered: 02/26/05
Posts: 367
Loc: NJ
That's a good question...a #14 will drop you just as quick as a 500KCM...but I never sweat an outlet, only the service lateral...maybe it's because it's not something I do sitting on a spackle bucket
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#50709 - 04/12/05 02:57 PM Re: Volts, Amps, & Ohms
wa2ise Offline
Member

Registered: 11/29/02
Posts: 771
Loc: Oradell NJ USA
 Quote:
I never sweat an outlet, only the service lateral


You're probably thinking of the hazards of an arc blast, which a 15 amp circuit won't create much of. Compared to incoming power from the street.

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#50710 - 04/12/05 03:58 PM Re: Volts, Amps, & Ohms
e57 Offline
Member

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
 Quote:
quote:
--------------------------------------------------------------------------------
I never sweat an outlet, only the service lateral
--------------------------------------------------------------------------------

You're probably thinking of the hazards of an arc blast, which a 15 amp circuit won't create much of. Compared to incoming power from the street.


Years ago.... Closing a can on 20' ext ladder, and pushed through the tape on a kearny. Went off like a grenade! Knock me off the ladder, very luckily un-hurt. Had to fix the damage the next day, I shook so hard it took a few hours to get the nerve to climb the ladder. I wonder what the AIC rating of a can cover is?
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#50711 - 04/13/05 05:39 AM Re: Volts, Amps, & Ohms
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Yes, I find people who don't understand the relationship all the time, and assume that if you touch a 240V 30A circuit you're going to get 30 amps going through you.

It must be over a year ago now, but ECN regulars might remember that we discussed a thread on another forum where somebody was arguing just that point. He was saying that even on 12 volts you could get a massive shock if the current in the circuit was high enough. No amount of explanation would convince him otherwise.

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#50712 - 04/13/05 07:02 AM Re: Volts, Amps, & Ohms
dereckbc Offline
Member

Registered: 10/08/03
Posts: 158
Loc: Tulsa, OK
aldav53, it is called ohm's law, day 1 theory after algebra class. However the is a heck of difference between the terminals of a service transformer, and a branch circuit with 50-feet of #12 AWG wire after the main panel.

To learn this difference simply short out the terminal from L-N or L-L on a service transformer, then repeat at a receptacle (use an apprentice to make the connections). Measure the fire-ball produced from both and see if there is any measurable difference. If so, why?

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#50713 - 04/13/05 07:18 AM Re: Volts, Amps, & Ohms
aldav53 Offline
Member

Registered: 08/22/01
Posts: 547
Loc: Chandler, AZ USA
dereckbc,
True, thats because the #12 circuit trips the circuit when it reaches 20 amps. (remember thats basically 0 resistence).
But you still won't get shocked any different by touching either one. (providing "your" resistence is the same).

pauluk,
Good example on the 12 volts. A car battery is 12 volts and capable of hundreds of amps, but the voltage is too to draw it. Unless you lay a metal bar across it (0 resistence).
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#50714 - 04/13/05 07:24 AM Re: Volts, Amps, & Ohms
GETELECTRIC Offline
Member

Registered: 10/22/03
Posts: 178
Loc: toronto canada
I,m not so sure I understand myself. so you are saying that if i grabbed with one hand a 400a circuit and grounded myself out that it is the same as if it were 15a being that both voltages were 120.

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