Originally posted by FortAnthem
reply to post by Bedlam
10k ohms of resistance is not always present in the human body. It can vary based on the healthiness of an individual, how dry or wet they are and
even how tired they are at any particular time.
So, you think it makes a lot of difference here if she's got somewhere between 300 ohms to 10k of resistance, with 1.5MV of potential across her
hands? Really? A lower value just means that she's got to have even MORE current across her to get that potential - it's not helping your argument.
Another interesting point to consider is that in addition to acting like a resistor, the epidermis acts like a capacitor if placed in contact with a
piece of metal ...
It acts like a really leaky capacitor with a low punch-through voltage.
If her body was acting as a capacitor, the static electricity would have been building up on the outside of her skin and would not need to pass
through her body in order to discharge. The distance between her two hands could have equaled a potential difference and, if her two hands had unequal
static charges built up around them, the spark may have been natures way of equalizing the charge. It may have been that her body's resistance was
greater than the air's resistance at that time due to whatever weird phenomena that fog created in her area, allowing the charge to dissipate through
the air rather than through her body.
The cite you used is telling you that dry skin has a higher impedance, about 10k, with wet skin having less, about 300-1000 ohms. They're also telling
you that in the case of AC, especially very high frequency AC like, say, RF, the capacitance of the epidermis can bypass the ~4.7K dry skin resistance
and make dry skin pass AC current as if it were wet. However. we're still talking a 10K dry resistance.
Think a 4.7K resistor in parallel with a small cap of a few hundred pf, that group in series with a 300 ohm resistor, then another 4.7K in parallel
with another small cap. Even with the caps there, it's still about 10K.
You can't get a static differential across it. Also, the epidermis doesn't have a >1.5MV breakdown voltage. If you got 1.5MV on "the outside of her
body" so that you had 1.5MV potential difference between hands, even if she had the world's least leaky epidermis, it would have punched through and
Her body is not a conductor, it is a resistor with various levels of resistance throughout the various parts of the body. It would be very possible
for a potential difference to build up on her body, especially in a statically charged environment. A conductor is a material that allows electricity
to flow freely through it, like copper. Skin, with a resistance of 10k ohms is, by definition, a resistor.
Resistors are conductors. Just not as good as a perfect conductor. Even copper is a resistor, I use copper strap resistors for current measurement all
the time. See also: current shunt.
A potential difference across a resistor causes a current flow. As I pointed out, the current will be E/R. If E = 1.5MV, and R is about 10K, then I =
150A, in order to sustain that potential difference.
edit on 12/18/12 by FortAnthem because: Doh! Forgot the link.
edit on 18-12-2012 by Bedlam because: (no reason