Re: lightning dangers

["L. R. Cartwright (Larry)" <physics@SCNC.CPS.K12.MI.US>]

The typical rooftop TV antenna is no lightning rod.  Many of them aren't
even grounded except for whatever path might exist through the receiver.

I think the reason lightning rods have fallen out of use is that there is
no longer good reason to go to the trouble.  Residential buildings are
rarely lightning targets.  Lightning prefers trees (90% water) and metal
structures as well as direct hits to the soil.  All of the overhead
powerlines that have become part of our neighborhoods provide another
attractive discharge path.

The use of lightning rods on houses in the first place was a form of fire
protection.  In the absence of all but the most primitive fire-fighting
equipment, almost every structural fire was a financially devastating
complete loss to the owner, and a threat to the entire neighborhood.  It
didn't matter that the chance of your building being hit by lightning was
minimal;  the potential consequences were so horrible to contemplate, you
would do anything practical and affordable to prevent that from happening.
The presence of competent local fire brigades and availability of
inexpensive fire insurance have pretty much eliminated any compulsion to
install lightning rods.

Best wishes,

Larry

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Larry Cartwright
Physics, Physical Science, Internet Teacher
Charlotte High School, 378 State Street, Charlotte MI 48813
<physics@scnc.cps.k12.mi.us> or <science@scnc.cps.k12.mi.us>

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On Thu, 29 Apr 1999, Oren Quist wrote:

> A question that I like to ask my classes is, "Why are there so few (no)
> lightening rods on houses any more?"
>
> My answer, which I say I am unsure of, is that in the 50's through 70's,
> all houses had lightening rods on them -- call TV arials.  During this
> time, the lightening rod manufacturers went broke, or made TV arials.
>  Now with TV-Cable and/or sattelite dishes, the need for lightening rods
> has returned, but no one has stepped in to produce them.  ???
>
> But, there is probably a better explanation. ???