Date: Fri Jun 27 16:57:25 2008 Back to Contents

Author: chuck britton

Subject: Re: Lightning


On Jun 27, 2008, at Jun 27(Fri) 1:27 , Jerry DiMarco wrote:

> If objects are taller than 50 yards, then they make a difference in
> where the lightning strikes.
> So it would appear that a lightning rod is going to be ineffective
> on objects taller than 50 yards.
I am , as yet, totally unable to follow the above implication.

> Here is an excerpt from the above webpage:
> "Lightning comes down out of the cloud randomly. And then when it
> gets within about fifty yards of the ground the electric field from
> the downward-coming charge makes the electric field so large at the
> ground that upward-going discharges leave all the sharp points such
> as tree tops and so on. And one of those meets the downward coming
> leader from the cloud. And that's what determines what gets struck.
> And so what exactly makes the upward leader and how that gets
> started... that is the physics of what gets struck."
> Jerry

Tall structure are going to get hit - period.

A lightning rod SYSTEM is going to include a very low impedance path
to ground.
Tall structures have rods to direct the charge flow to this low
impedance path to ground.

any other path to ground will result in great damage.

From Fri Jun 27 16:57:25 2008