Grounding Quiz, by Mike Holt

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Re: Grounding Quiz, by Mike Holt

Question #33 asks if you are more likely to be electrocuted in salt water than fresh water.

I was always under the impression that the reason that you can get electrocuted in the tub is because the salt from your sweat makes the bathwater more conductive. Otherwise freshwater is a really bad conductor.

Based on this assumption, swimming in a fresh water lake or river and having the power pole tip into the water some distance from you probably wouldn't be too much of a hazard. Your sweat is localized and would stop shortly after the swim began unless the water is hot. And the current has to get through all that insulating H2O to get to you.

A body of salt water would behave somewhat like a big grounding system, taking the current to ground. Even if it didn't, it would likely keep your whole body at close to the same potential, limiting current flow through you. In other words, it shorts you out.

The tub hazard is due to limited water volume, your sweat salt, and that metal pipe underfoot tied to the grounding system of the house.

Which begs another question, what if the piping in the tub, in and out, is all PVC?

Matt
 
Re: Grounding Quiz, by Mike Holt

The salt water is more conductive and that makes it a bit safer than fresh water. In both cases the water is a conductor and the person in the water is a second conductor in parallel. Because the salt water is a better conductor, there is less of a voltage drop over the length of the person so the person is subjected to a lower voltage. The reason that you get shocked in water is not because its, a good conductor, but because it is a poor conductor. If it was a good conductor you would be safe just like a bird on a wire.
Don
 
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