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lightning

In article <4u024g$1q4@lyra.csx.cam.ac.uk>,
Edmund Grimley-Evans <etg10@cl.cam.ac.uk> wrote:
>                                           As the dark clouds
>moved overhead and just before the rain began to fall I was aware
>of a strange humming noise that seemed to come from the lightning
>conductors (but there are four of them so it was hard to tell).

As far as I know, the main purpose of lightning conductors is not, as
most people assume, to provide a safe path to earth should lightning
strike the building.  Rather, they help to prevent lightning in the
first place: the conductor allows charge to move between earth and the
clouds, neutralizing them.

If this is correct, then during an electrical storm there will be a
continuous current through lightning conductors.  This could account for
the humming that you heard.  (Although I'm not sure that I'd expect DC
to hum.)

This is (half) remembered from A level physics many moons ago.  Can
anyone who knows what they're talking about correct or confirm this?

Tim.
--
Tim Goodwin   | "USENET, of course, is a pure and unadultered source
Cambridge, UK | of truth and wisdom." -- Richard Kettlewell

Original headers:

From: tim@pipex.net (Tim Goodwin)
Newsgroups: cam.misc
Subject: Re: lightning
Date: 5 Aug 1996 12:13:46 GMT
Organization: Unipalm PIPEX
Message-ID: <4u4ohq$g2h@wave.news.pipex.net>
References: <4u024g$1q4@lyra.csx.cam.ac.uk>

△ Cam.misc △

◅ Cycle & pedestrian railway bridge, council comment?

Hydrocarbons: ▻