Lightning rods-glass balls?
heidi crandall
Are the glass balls I see on home and barn lightning rods purely ornamental,
or do they serve a purpose ( perhaps they shatter when the rod is hit by
lightning?)
Thanks!
--
Heidi Crandall
work: Ford Motor Company, Dearborn, MI >>> cran...@itc116.be.ford.com
play: Northville, MI, zone 5
dvi...@iadfw.net
> Are the glass balls I see on home and barn lightning rods purely ornamental,
> or do they serve a purpose ( perhaps they shatter when the rod is hit by
> lightning?)
>
Glass balls?
Those rods should end in a sharp point. The idea being to bleed off
static charge build up BEFORE a lightning strike becomes possible.
John E. Taylor III
>
> > Are the glass balls I see on home and barn lightning rods purely ornamental,
> > or do they serve a purpose ( perhaps they shatter when the rod is hit by
> > lightning?)
>
> Those rods should end in a sharp point. The idea being to bleed off
> static charge build up BEFORE a lightning strike becomes possible.
Yeah, the tips of the rods are pointed; the glass balls are about half-way
down the rods. I've always considered them purely decorative, as I see no
good reason in physics to have them.
--
John Taylor (W3ZID) | "The opinions expressed are those of the
e-mail: mah...@rohmhaas.com | writer and not of Rohm and Haas Company."
Robert Plamondon
>> or do they serve a purpose ( perhaps they shatter when the rod is hit by
>> lightning?)
They complete the phallic symbolism of the lightning rod.
-- Robert
P.S. Color is also meaningful. Blue balls indicate that the contractor
who installed the lightning rod was not impressed by the state of the
marriage of the householders, for instance.
P.P.S. Don't confuse these with brass balls, which are a weather
instrument, of sorts.
--
Robert Plamondon * Writer * rob...@plamondon.com * (408) 321-8771
4271 North First Street, #106 * San Jose * California * 95134-1215
"Life is like an analogy."
Todd Rossman
Very good question (for trivia.)
My grandfather told me that the glass bulbs on lightning rods
will kind of glow or irradiate a blue ring around them before
lightning strikes the barn.
The early waring device was not very early though. There is
ususally only about 5-30 seconds notice, or lightning may not
strike at all.
At any rate, if you see the blue glow around the glass bulb and
are putting shingles on the roof, GET OFF. :)
=======================================================
Name: Todd Rossman
E-mail: tros...@bright.net
Save a farmer. Bag an activist.
________________________________________________________
Chris Beckmeyer
>In article <3r01ba$i...@news.iadfw.net>, dvi...@iadfw.net wrote:
>down the rods. I've always considered them purely decorative, as I see no
>good reason in physics to have them.
I was told that the lightning sort of fractures and bounces around inside
the balls, providing some cool *Frankenstein-y* visuals.
Those Victorian folk had all kindsa fun :-)
John Byrnes
> I was told that the lightning sort of fractures and bounces around inside
> the balls, providing some cool *Frankenstein-y* visuals.
> Those Victorian folk had all kindsa fun :-)
This can be true anytime during a thunder storm, but it is due to the
electrical current running from ground into the sky and *not* lightning.
Lightning has enough power to change an excellent insulator (air) into
a very good conductor. A little glass ball (or little human body) isn't
going to affect it one iota.
To clarify a few things:
Lightning rods work two ways. First, they will discharge an area of sky
above the rod *before* lightning strikes, making it less likely your house
will get struck. It is in this situation that the little glass balls can
glow.
You need many rods (not one or two), an excellent connection of the rods
to ground (a lot of electrical current flows from the ground to the sky),
and it doesn't always work.
Secondly, if lightning decides to strike your house anyway, the rods/cable
provides a easy path to ground for the current, minimizing damage to the
structure. "Minimize" is relative :-)
John
Mike Ryer
net "wisdom" from the last time this was discussed. As a person with some
slight engineering background this explanation makes a lot of sense to me.
According to the net,
The main purpose of a lightning rod is to prevent lightning strikes. It does
this by dissipating the charge in the ground (charge relative to the sky, that
is). Dissipation of a static charge depends on the radius of curvature. A
pointed metal object is ideal. A ball is terrible. The purpose of the ball
on the lightning rod is to collect static charge from the ground. Then the
needle above it dissipates that charge into the air. No potential difference
implies no lightning strike. The rod protects a 45% cone below its peak.
The glow is "St. Elmo's fire". What you're seeing is the dissipation of the
charge. If you see it, duck.
If lightning hits your rod, you've got gigawatts flowing to/from the ground
through your lightning rod. Unless it's solid copper about six inches thick,
it's going to vaporize instantly. So much for minimizing damage.
When I built a house, I asked the electrician what to do about lightning
rods. He recommended building a really super one (six ground rods) about
five hundred feet *away* from the house, so I could sit in my living room
and watch the lightning hit. Needless to say, I didn't bother.
It appears that lightning rodding is a voodoo-ridden branch of engineering.
-- Mike "don't take *my* word for it" Ryer
Bill Sloan
(Mike Ryer) wrote:
(ZZZZZAP!)
#
# It appears that lightning rodding is a voodoo-ridden branch of engineering.
#
# -- Mike "don't take *my* word for it" Ryer
With all this discussion of lightning rods, Look up what Mark Twain had to say
on the subject - voodoo indeed.
Bill Sloan
John Byrnes
> If lightning hits your rod, you've got gigawatts flowing to/from the ground
> through your lightning rod. Unless it's solid copper about six inches thick,
> it's going to vaporize instantly. So much for minimizing damage.
This is not always true. If it were, we'd never hear of someone surviving
a direct lightning strike (but we do).
According to what I've read, there are two kinds of lightning; "hot" and
"cool". Most bolts are cool. A cool bolt does not have much current/
power in it (for a lightning bolt!). A lightning rod system can minimize
damage from a cool bolt by diverting it down the cables to ground. Since
most bolts are cool, this is frequently effective. It is not unheard of
for there to be *no* damage from a direct hit.
A hot bolt, as you say, will pretty much vaporize whatever it hits. It
has a lot of current/power and there's not much you can do to protect
against it. Luckily, these are much less common.
> When I built a house, I asked the electrician what to do about lightning
> rods. He recommended building a really super one (six ground rods) about
> five hundred feet *away* from the house, so I could sit in my living room
> and watch the lightning hit. Needless to say, I didn't bother.
Good thing, you would've wasted you money. There have been many studies
and experiments done trying to determine *why* lightning strikes any
particular place. Only gross guidelines have been established. For
example, we all "know" that a lone tree on a flat golf course is a likely
target. What tree will it hit if there are a dozen trees?
A hill on a plain is a likely target, but in a hilly region lightning will
sometimes strike in the lowest part of a valley. How does lightning decide
where to strike if there are *no* trees or hills or houses?
My point here is that your electrician was wrong two ways. A remote
system will not reduce the likelihood your place would be struck (by
"attracting" lightning), and two, provides no protection if it was hit.
> It appears that lightning rodding is a voodoo-ridden branch of engineering.
Hey! Don't deride us engineers! Lightning is still a "science" in that
people study it, but don't understand it, nor can they control it. When
I can stand on a hilltop and throw lightning bolts at people I don't like,
THEN it will be engineering! ;-)
John
