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Re: lightning dangers



Hugh and Carl:

We had a lightning expert present at a recent Az-AAPT meeting. The danger
is real. A lightning strike on a house will likely exit through plumbing
or electrical connections, and the huge voltages are fairly localized
to narrow paths. If you have part of your body on and off one of these
paths then you get a big voltage differential set up in you too. His
advice was stay away from appliances and plumbing durign lightning storms.

We also discussed phone use during lightning storms. Most people killed
inside houses by lightning are using the phone when they get zapped. We
discussed the opportunity presented by obtaining a cordless phone and
calling people you don't like during storms to see if you could win the
lottery so to speak (cheap yet fun)! Apparantly the danger is real enough
he felt the phone company should be printing warnings in their directory.

Finally, he showed a burn pattern on a grass golf green after a direct
strike on the golf flag. The pattern looked like a bifurcating fractal
across the surface of the grass -- the strike stays pretty shallow. One
foot on and one foot off this pattern would be traumatic indeed.

Dan M

PS -- from the LPA minutes at http://purcell.phy.nau.edu/AZAAPT/Spring99r.html:
"
Our final invited speaker was Phil Krider, from the UA Atmospheric Physics
Department. His presentation, titled Lightning--A Striking Phenomenon,
described what is currently known about lightning, how best to achieve
protection against lightning strikes, and his current research in
rocket-triggered lightning.
"

Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ
danmac@nau.edu http://purcell.phy.nau.edu PHYS-L list owner

He showed
so>
From time to time, someone will mention that it's dangerous to take a
shower during a lightning storm. I'm assuming the idea is lightning could
strike a tree or the ground nearby just as I put my hand on the tap. This
doesn't seem like a terribly high risk to me, as I tend to think of
plumbing pipes as generally being rather well grounded. But let's hear what
you think. Is this an urban myth? Has anyone heard of any actual cases of
electrocution this way? Carl

Dr. Carl E. Mungan, Assistant Professor http://www.uwf.edu/~cmungan/
Dept. of Physics, University of West Florida, Pensacola, FL 32514-5751
office: 850-474-2645 (secretary -2267, FAX -3323) email: cmungan@uwf.edu

Interesting question. I have had some of the same doubts myself. I know
that at our community swimming pool, they close the pool anytime there are
thunderstorm activites in the area, and my understanding is that a nearby
lightning strike can create large transient currents which could find their
way into the water in the pool. But it seems a stretch to think that these
transients could also make their way through the plumbing. Maybe they can.

Hugh

********************************************************************************
Hugh Haskell

<mailto://haskell@odie.ncssm.edu>
<mailto://hhaskell@mindspring.com>

The box said "Requires Windows 95 or better." So I bought a Macintosh.
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