Lightning & Bathtubs

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On Fri, 06 Jun 2008 16:46:11 -0700, w_tom wrote:

Thats incorrect. And blunt rods being better would be some remarkable new science.

Ligntning rods do not stop lightning. They are a deterrent only. You show a lack of understanding of the fundamentals of static electricity. What you state as fact is only 1/2 true. What you refute is equally 1/2 true.
The lightning rods deterrent behavior does not require it have the best ground, only a sufficient one. The lightning rods attractant behavior requires it to have the better ground. Still, with the amount voltage you will see energy going through both paths to ground.

Wrong. Its effectiveness as an attractor is tied to the quality of its earth ground. Its effectiveness to leak off static electricity is tied to its shape, and the ground as well. but the ground does not have to be the best around, just sufficient.

If you discharge the static electricity, then you can stop lightning. So the claim that discharging the clouds/ground will stop lightning is 100% scientific and correct. The flaw is that you can't guarantee that you can discharge it fully, or continuously or fast enough.
We may share the same resonings because what I state is based on the laws of physics. So my statements are true. However, I am not reaching the same conclusion. I doube the reasoning was rejected but more likely they decided the conclusion did not follow from the reasoning.

"No sharp bends" you realize why this is right? Same principle as leaking off the static charge.

I agree. If you are further claiming that the act of leaking off static charge has been proven ineffective, then I will accept that.
CL
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Your statements are based in popular myth - with no basis in laws of physics. Is it knowledge because the urban myth is popular? That same lesson (flawed but popular reasoning) also proved Saddam's mythical WMDs. A fact does not exist due to popular belief.
First, the myth is that sharp (pointed) rods are better. Science and numbers say blunt rods make better lightning rods. From a 1999 paper in Journal of Applied Meteorology by Moore, Rison, Mathis, and Aulich (published May 2000):

Second: myth that a lightning rod dissipates static charges also was repeatedly criticized as junk science. From Wikipedia:

Numerous peer reviewed papers also discredit that "discharge the static electricity, then you can stop lightning" theory. Again, NFPA was quite blunt about it. There exists zero supporting facts or research for this "discharge the static electricity" myth. None. NFPA said:

Even worse, that 'discharge the air' theory creates a human safety risk. From Hartono and Robiah entitled "A Long Term Study on the Performance of Early Streamer Emission ...":

Furthermore:
If those ESE terminals discharged air, then why so many lightning strikes even near the ESE air terminals? Because air terminals that discharge static are based in junk science reasoning.
Not only was the NFPA roundly critical of that 'discharge the air' myth. NFPA also cited numerous studies (ie Hartono and Robiah) that showed "discharge the static electricity" devices provided NO protection. Speculation that lightning rods protect by discharging the air is only junk science and is not found in science. We learned this same lesson from history: Saddam's WMDs. Popular belief does not create fact. Facts come from learning the science. Static discharging does not provide protection.
How many sources completely discredit this 'discharge the air' myth? Science (laws of physics and experiments) says blunt rods are superior. Discharging inches of air around a lightning rod neither stops nor averts nor reduces lightning strike frequency. Lightning strikes are made irrelevant by connecting / diverting / channeling / conducting that inevitable lightning strike into earth. Protection is about dissipating that energy harmlessly in earth. That energy must be dissipated somewhere. Inside a building (destructively) or inside earth? Discharging static charges is the same logic that also proved "Saddam's WMDs" - junk science reasoning promoted by popularity. How many science sources need be quoted?
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On Sat, 07 Jun 2008 19:44:08 -0700, w_tom wrote:

No, my statements are based on scientific fact. The laws of physics. It is knowledge because I have a 4 year Electrical engineering degree. Not because I over heard some myth.

I did not say sharp pointed rods are better. I said they would discharge static. And they do. Just a blunt rods let static build up. Which they do. In a contest of who gets the most lightning strikes a blunt rod naturally will. By definition. The point rod attempts to reduce the number of strikes anyway. The blunt would do just the opposite.

Sorry, it is fact that static will be released through a pointy rod more than it will through a blunt one. Its not myth. I can't say if this makes it better at reducing the number of strikes. I'm not making that claim.

Thats fine since I don't claim rods stop lightining.

ESE system is different from pointy grounded rod.

No offence but you still show a lack of understanding of the fundamentals. This is not junk science. its sound theory. Even if its proven incorrect.
You are still conflating lightning attraction with static dissipation. pointy rods are better at dissipation. This is scientific fact. This is not myth. Round rods being better at protection I still will not agree with. Maybe they get more strikes, but they can artifically create additional strikes simply by being blunt. Any lighting creation device will be blunt.
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dnoyeB wrote:

It is true that if you have a sharp point at high voltage, there is a high electric field around the point that can break down the air and ionize it. It does not follow that a sharp point will significantly dissipate/neutralize the charge creating lightning and prevent lightning strikes at a rod.
The concentrated charge primarily accumulates in the cloud. If you are discharging the "static electricity" you are neutralizing the charge in the cloud. You assume there will be enough current from the point to dissipate that charge. I have seen no reason to believe that is true. A paper at http://www.lightningsafety.com/nlsi_lhm/magic.pdf writes about the problems of emitting charge from a sharp points. Just one of the problems is that, for most lightning, you are creating positive ions which are not particularly mobile.
A paper at http://www.lightningsafety.com/nlsi_lhm/charge_transfer.html is about a scheme (CTS) emit charge from sharp points to protect an area from a lightning strike. A conclusion in the paper is "The undeniable facts are that 'dissipation' devices do not prevent the occurrence of cloud-to-ground lightning strikes..." The system may, or may not, reduce the probability of lightning striking a rod. That is not necessarily an advantage. There will be as much lightning, and it will strike something. The point (if you excuse the expression) of rods is to provide a relatively safe place for lightning to strike.
---------------------- "No sharp bends" is because of inductance, not "leaking off the static charge".
--
bud--



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On Sun, 08 Jun 2008 02:35:52 -0500, bud-- wrote:

I am not claiming a lightning rod will prevent lightning strikes at the lightning rod. You can't both blead off static charge and be resistant to passing large qualtities of static charge at the same time. AFAIK.

Nope, because I have not claimed a lightning rod will prevent lightning. Only that it dissipates charge. Not that it dissipates enough to stop a lightining strike. Are you saying it does not dissipate any, or that a lightning rod has 0 effect?

Well that is the conclusion that Is hard for me. That there will be as much lightning. If it is, then it is. You learn something every day. Ill have to look into it. Maybe today is my day...

Inductance is in a way resistance. When lightning finds resistance, it can choose an additional path. The result is the same.
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And we call that discharge 'lightning'.
--
FF

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Good explanation and thanks for the citations. I think there is also something to be gained by looking at the sequence of events. From what I have read, for most cloud-to-ground strikes you first have a dart leader descending from the cloud in stepwise fashion. (you can sometimes hear it as the crackling or 'cosmic zipper' sound before the main boom of a nearby strike) When the dart leader gets within a hundred meters or so of the ground, the local static field becomes very intense and things on the ground within a 50 or 100 meter radius beneath the dart leader send up small positive-ion streamers. When one of these connects with the dart leader then the channel is complete and the main discharge begins. So in essence, meteorological events determine where and when the dart leader comes down, and when it nears earth then there is a sort of target zone beneath it; only then do conditions on the ground come into play to determine exactly where in that target zone will the strike occur.
As for what makes for a vigorous ground streamer that is likely to connect up with the dart leader, I don't think I have seen any articles on that. Anecdotally, I know when I lived in an area with well and septic water systems, people used to often talk about their wells being struck by lightning. That would seem to argue that good grounding is a factor, since the well (an iron pipe sunk a couple hundred feet into the ground) only stuck up maybe six inches or so, and certainly there would be taller structures (trees, houses) nearby. -- H
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On Tue, 10 Jun 2008 10:44:30 -0700, Heathcliff wrote:

I think if its researched what will make a good ground streamer will have to do with the "ground plane size." That is, how much opposite charge is available to be reached in that area and how quickly. In a sense, the quality of the ground. Not necessarily tied to the depth of the ground plane. But the whole volume.
I wonder if thats a good way to identify underground water sources in the dessert!? Not that you would want to be close enough to see the strike. But maybe the scortched ground can reveal something.
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did you ever see that PBS NOVA show on lightning? the show was very good. it's probably due for a re-run for this year's storm season.
some universities doing lightning research shot rockets that trailed a thin wire into cloud formations that indicated a high charge state,trying to induce strikes and then checking the effects upon a small power grid at their launch site.
The strikes would create fulgurites;glassy fused soil or sand,in wierd shapes.
--
Jim Yanik
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Maybe so, but residential lighting rods are electrically isolated from the rest of the house.

Yes. That is how they work. The lightning strikes the rod and goes to ground through the grounding cable attached to the rod, instead of the house being struck.

That is correct IF you consider the lighting rod to be part of the building. Lighting rods attract lightning and conduct the current safely to the ground without passing through any OTHER part of the building.

No.
--
FF


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On May 31, 1:20am, snipped-for-privacy@invalid.com wrote:

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