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I agree with John,
When I was a boy at a summer camp in West Texas there was a single
wire electric fence surrounding the croquet courts to prevent the
cattle and horses from making the sport much more difficult.
The older campers knew that touching the electric fence would hurt,
but grabbing it quickly and whole-handed produced an irritating pulse
(T~0.5s) in the wrist. The sensation was tolerable and contact with
the fence could be maintained.
During capture the flag the trick would enable one to run deep into
enemy territory and be safe from younger campers who did not want a
shock from tagging the 'fence squatter'.
Sneakers were key. If blades of grass touched tickled the ankles,
they would sting. The older campers would also take revenge on each
other. Grabbing the hand of a 'fence squatter' and then kneeling
would make holding on intolerable - for both. The latter trick was
probably not the safest in retrospect, but it was part of the camp
culture.
I have repeated the trick later in life to amazement of others. Some
fences are more intense than others; however, it feels nothing like
the times I have hooked my self to 110V (accidently - of course).
I have often wonder if the shock effect is similar to physiological
effects of acceleration or loud noises. How much does the onset of
the shock determine how intensely the shock is felt?
Scott
*******************************************
Scott Goelzer
Physics Teacher
Coe-Brown Northwood Academy
Northwood NH 03261
sgoelzer@coebrownacademy.com
*******************************************
On Aug 27, 2006, at 12:44 PM, John Denker wrote:
> Regarding electric fences, Matt Coia wrote:
>> I'd equate it to getting zapped with 110v in a house. It
>> certainly gets
>> your attention.
>
> I would not make such an equation. I would certainly not say anything
> like that in front of students.
>
> Fences are not 100% safe, and 110V wires are not 100% lethal, but if
> you look at the probabilities, you will see that 110V wires are vastly
> more dangerous ... even if you take unequal exposure factors into
> account.
> The last CPSC figures I saw were something like 200 household
> electrocutions
> per year (down from 700 per year in the 1970s).
>
> Electric fences are designed so that touching them "should" be
> nonlethal
> under all conditions. The rules for 110V wires are completely
> different;
> the design rule is that you "should" not touch them (without proper
> insulation) under any conditions.
>
> =============
>
> Please, folks, let's get this one right. This is one of the few
> topics
> that comes up in physics class where misinformation can be directly
> life-threatening. (Another such topic is the physics of driving
> cars.)
>
> There is much room for improvement.
>
> For example, in Sears, Zemansky, & Young there is a multi-page
> discussion
> of household wiring that is just appalling. They evidently don't
> understand
> the distinction between "neutral" and "ground". The wire that is
> functionally
> neutral is called ground, and is diagrammed as grounded in
> multiple places ...
> which would be unsafe, not to mention being in violation of code.
>
> They go on to give an incorrect description of how a GFCI works.
>
> It's true that familiarity breeds contempt ... but that doesn't
> make it any less
> dangerous. 110V wiring is not to be trifled with. For those
> "lucky" enough to
> live with 220V mains, this is even more important.
>
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