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Re: [TCML] Lightning?

Hello group,
Altho slightly off topic I take it everyone here likes big sparks.Believe me being close to a lightning strike isn't my idea of fun.I have been too close to a strike twice in my lifetime and I believe the figure you are looking for is about 15 feet according to my experience.There are probably a lot of factors involved tho. The first time I had disconnected the coax from my CB radio and coiled it up on the wooden second story floor just above a ss sink on the first floor. The strike went through the floor hit the sink which I was standing beside,bounced off that and formed a ball that seemed to stop in the middle of our kitchen and then flew into a screen door where it exploded leaving a hole in the screen. All the while my hair stood on end and I felt little sparks all over my body.The other time I was outside and the main bolt hit a tree 25 feet away and a branch hit about 12-15 feet in front of me. That time the sparks came up thru my feet and gave me one heck of a shock but the worst part of it was the shrapnel from gravel that penetrated my skin. That really stung like I had just gotten attacked by a swarm of bees.Hope that helps with your research.. Binny

-----Original Message----- From: jhowson4@xxxxxxxxxxx
Sent: Tuesday, June 19, 2012 8:58 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Lightning?

Thanks for the excellent answer Jim. I appreciate it!

I was unable to locate the strike zone today, no apparent damage anywhere on the house or in the surrounding foliage. So i guess it hit the ground of which none of the grass in the area appears to be dead, yet... If it did hit the ground I would really like to find the fulgerite, if it even exists in our soil, but i am not holding my breath for such a find.

I still think there is an estimated finite radius for a significant effect though, especially for a the singular pulse that lightning is. I mean you don't see stuff fairly far away exhibiting these effects of induced charging, via electric or magnetic effects. They both would have a localized area which would depend on the current and charge densities present during the strike.
But what the average size of that area is, i dont know.

John "Jay" Howson IV

"Why thank you, I will be happy to take those electrons off your hands."

----- Original Message -----
From: "Jim Lux" <jimlux@xxxxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Sent: Tuesday, June 19, 2012 9:47:37 AM
Subject: Re: [TCML] Lightning?

On 6/19/12 1:40 AM, jhowson4@xxxxxxxxxxx wrote:
Hello all,
At the moderators discretion I have a quick unrelated question for you guys,

A wicked storm just rolled through here in Rochester, and I was standing near the window looking out trying to capture a few nice bolts on my cell phone camera. well one happened to hit extremely close by. Close enough that I physically felt a spark jump from the window or the blinds or something in that area to my chest. Perhaps2-3 inches long. It felt something like a nice big vandergraaff shock. Scared the heck outa me.


I am trying to figure the radius of effect for a lightning strike, how close does one have to be to the main event in order to experience induced charging and the like. I will go out and look for damage tomorrow, but nothings on fire that we can see so i don't know what we will find. The other option would be that I just so happened to be a part of a failed leader stroke and the charge reached out to connect with the main but didn't, Hench the small none killing me spark. and the main event was a little further away that I though. I tried poking around the internet but I cant find anything that specific with number, just general "they can cause induced charges on nearby objects"

Maybe one of you guys knows more specifics on the subject and could share your knowledge,
Contact me off list.

It's relevant to TCs, because the whole area of induced voltages and
currents is how things get fried by TCs, when we don't want them to.

First off, there's no specific "radius" for a spark effect, whether from
lightning or something else.

several aspects to be concerned about..
First, any time you have a current flowing in something, there's a
voltage drop, partly due to resistance and partly due to reactance
(inductance mostly).

For lightning and TC sparks, which have fast rise times, inductance in a
current path can lead to surprisingly high voltages. Consider that
lightning (at the end of the stroke) is basically like a constant
current source, so the di/dt is driven externally (nothing you do is
going to change it).

The voltage is L di/dt.. for a typical stroke the rise time is around 1
microsecond. For a TC, the rise time on a spark is nanoseconds.
However, the lightning stroke is on the order of 30kA, while I doubt the
TC current is that high.

In any case, you're looking at a di/dt in the 1E9-1E10 amps/second range.

Inductance for most conductor shapes is pretty close to 1 uH/meter, so
you get several kV/meter for anything that lightning is flowing through.

(including the soil!)

That potential difference can induce a voltage in nearby objects, just
as standing next to a Van deGraaff generator or TC can induce a voltage
in you. This can either be a classical electrostatic induction effect,
or, I think, more like a capacitive coupling thing... you have a dV/dt
of several kV/microsecond, and with even a few picofarads, you can have
significant current flow, which in turn can lead to charging of a
counductive thing that's insulated, otherwise.

Once that "thing" gets enough charge on it, it can spark over to
something else at a different potential, or to the air (just like off a
TC topload).

Then, there's the magnetic field effects. That kiloamp current flow
creates a hefty magnetic field, even if it's only a "one turn" coil.
That rapidly changing field can induce voltages in a "victim loop"
formed by, say, the grounding wires on some equipment and the cables
interconnecting them. (imagine a computer and printer, each chassis
grounded thru the plug, with a cable between them, also grounded to each

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