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MMD > Archives > May 2002 > 2002.05.31 > 01Prev  Next

Technically Dead? I Guess Not!
By John A. Tuttle

Hi All,

My sincere thanks to all who have responded to my query about why
Pandora and I didn't get electrocuted.

Just for grins, I did a little experimenting to discover the normal
resistance of "pure water" and salty water. I placed the test probes
three inches apart. Here's what I found.

Our "tap water" must contain a fairly significant amount of chemicals.
Using my standard (battery-powered) VOM, I found that at three inches
separation (the probes), there is 20K ohms of resistance. My body, if
wet, has 50K ohms of resistance, as measured between my wet foot and
my wet hand. If my feet are wet but my hand is dry, the resistance
increases to 200K. So it's pretty obvious that the path of least
resistance would have been between the submerged prongs of the
extension cord...

Next I measured the resistance of the devices that 'were' plugged in.
They are both over 1 meg ohm (DC resistance).  I do believe there is a
difference between AC and DC resistance...  Still, the path of least
resistance would be between the two submerged prongs of the extension

Next, I added one tablespoon of salt to the six ounces of water in the
'test bowl'. The resistance dropped to 2K ohms.  Realistically
speaking, to achieve that level of saturation (or contamination),
there would have to have been about 200 pounds of salt in the 750+
gallons of water on the floor to reduce the resistance to 2K ohms. I
venture to say that the resistance (at 1/2" separation... as with the
extension cord) was in the neighborhood of 20K because there were no
real contaminates in the basement... except for the small amounts of
detergent that have been spilled on the floor over the past 10+ years.

So, I've learned that our tap water does indeed conduct electricity.
So, it's anything but "pure"... yuk! However, even when wet, my body
(and Pandora's too) are not much of a conductor as compared to the
submerged prongs of the extension cord. Further, adding contaminates
to the water would have created a less resistant path at those contacts
as compared to our bodies.

Again, I want to thank everyone who responded to my questions.


John A. Tuttle
Brick, NJ, USA

BTW, we do have GFCI in our bathrooms and the kitchen. I never figured
GFCI was needed in the basement, but I'll most likely install GFCI
right at the fusebox just in case of future problems.

(Message sent Fri 31 May 2002, 15:53:35 GMT, from time zone GMT-0400.)

Key Words in Subject:  Dead, Guess, I, Not, Technically

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