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As in most other potentially hazardous exposures time is a factor.
If I remember correctly one can conduct 10 amperes for 1 microsecond from a
van de graff generator and be unharmed. Done it myself hundreds of times.
Bill Norwood
U of Md at College Park
On Tue, Dec 18, 2018, 8:47 AM Paul Fedoroff via Phys-l <
phys-l@mail.phys-l.org> wrote:
How about just saying Power?electrical
On Tue, Dec 18, 2018 at 8:27 AM Peter Schoch <pschoch@fandm.edu> wrote:
Hello,
I have always used the phrase "current kills" when discussing
I={\fracsafety for my lab safety lectures. One of my references is:wrote
https://www.physics.ohio-state.edu/~p616/safety/fatal_current.html
Now, one of my students has found:
http://www.electroboom.com/?p=450
that contradicts it. In response to this video, a thoughtful student
me the following:
"...here are my calculations and conclusions: ohms law: [image:
resistance.{V}{R}},] states that current is equal to voltage divided by
.01This means that current is limited by by the voltage of the circuit andthe
inverse of the resistance of the circuit. That being said, humans arenot
good conductors, relative to metal such as in wires. In fact, a typical
resistance for 'human' is anywhere from 500(very wet skin)- 100,000(dry
skin) Ohms. For comparison, a typical wire is usually around the .1 -
isn'tohm range, meaning that there is a minimum of 3 orders of magnitudeeven a
difference between the resistance of wet skin (e.g. your tongue) and
bad wire. Thus, if you have a power supply producing 10 volts, even ifthe
current it can produce is infinite, the maximum that could run throughyour
tongue is given by: [image: LaTeX:This
I=\frac{10}{500}=.02\:amps\:=\:20\:miliAmps]I=10500=.02amps=20miliAmps
is enough to hurt and even cause strong muscle contractions, but it
exactlyenough to kill, which is 60 miliAmps (for DC it is actually higher than
this), and this is on your tongue. In fact, in the video, this is
dampwhat Mehdi Sadaghar does to himself. However, for dry or even mildly
"currentskin, this value would be < 1 miliAmp, which would not even be felt. So
while it is in fact the current that kills you, saying only that
people,kills, not voltage" is similar to saying that cancer doesn't kill
completelyorgan failure does. While this isn't strictly wrong, it isn't
alsotrue either, and it can give people the wrong impression. This would
voltageexplain why warning signs say 'High voltage' not 'High Current'."
While I agree that you can't have a current without a sufficient
toweek
move it, they don't 'discover' that in lab until the second or third
with(the first week or two being spent on just familiarizing themselves
inthe various peices of equipment and what they do).kills"
Ultimately, my question is -- Should I stay with my simple "current
message to drive home the necessity for safety; or, should I ammend it
_______________________________________________some way?_______________________________________________
Thanks,
Peter Schoch
_______________________________________________
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Forum for Physics Educators
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