From Andrew A. Montgomery
I am confused by the implication of Jeff Hecht’s article on sharp and blunt
lightning conductors
(May 27, p 10).
Surely the main reason for having a lightning conductor is not to attract
lightning strikes but rather to prevent them happening by permitting a
continuous non-violent discharge to earth through a low-resistance conductor. So
the “competition” referred to would seem to confirm that sharp rods work better
than blunt ones, since they were not hit.
I can confirm from my experiences with a school van de Graaff generator that
I can readily attract sparks to my rounded fingertip, but not to a pin held in
the hand, if I point them in turn at the dome of the generator.
Jeff Hecht writes: After 250 years, there remain some broad disagreements
over the function and theory of lightning rods, even among developers. One
theory is that lightning rods should drain charges gradually so that lightning
does not strike in the vicinity. However, a second is that lightning rods should
provide a channel for current to travel to ground or earth, diverting the
lightning strike from something that could be damaged, such as a building.
Lightning rods designed to meet the criteria of the second theory are supposed
to attract strikes.
Advertisement
That’s what the article described. As I understand it, the basis for diverting
rather than discharging is the assumption that the charge accumulating in the
clouds is too large to simply drain away, so the inevitable lightning strike
should be diverted to somewhere harmless.
Geneva
