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Michael Edmiston wrote:cut
* * * Typically-found Physics Description * * *
(1) Lightning rods are sharp
The foregoing were the "good" ones?
I started looking into this when a roofing firm was telling me about the subcontractor they use to install lightning protection on houses and buildings they roof. The lightning protection firm
says it is false that lightning rods prevent lightning, and it is also false that lightning rods
attract lightning. The only thing lightning rods do is route the lightning though a safe path.
Hmmm.
To me it seems inconsistent that the rods can route the lightning if they don't first attract the
lightning.
Yes, indeed: inconsistent.
bc agrees; see below.It appears there has been some legitimate research that lightning rods should not be sharp, but also not be "too dull." A sharp point is bad, a large conductive ball end is bad, but a radiused
rod (perhaps a 2-cm diameter rod with rounded top) is best.
I doubt it.
The experimental evidence is that sharp rods and radiused rods have been put on a mountain, and the only the radiused rods get strikes. The sharp rods do not get strikes.
http://infohost.nmt.edu/mainpage/news/2000/30may03.html
http://www.usatoday.com/weather/resources/basics/2000-05-15-lightn-rod-tests.htm
IMHO there are a lot of poorly-controled variables in that study.
How nearby is "nearby"? What would have happened if other rods hadn't
been nearby? I'm not sure all the authors' conclusions are well supported
by the data.
I've seen sharp rods and very unsharp rods, all of which got strikes.
It might be that the corona discharge from the sharp rod puts so many ions in the air around the end of the rod that the ion density is high enough over a large enough area that the sharp rod essentially appears as a rounded ball due to the space charge.
From there on, both things behave the same. If the space charge getscarried sideways or upward by advection or drift/diffusion, it effectively