Which material has high enough ohmage to resist lightning?

Hi:

Is there any material that has enough electrical-resistance to block off high-voltage such as that of lightning? Lightning is around a million volts.

Another question. Which material has the strongest electrical resistance of all?

Thanks,

Radium

Reply to
Radium
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5000 meters or yards of air.
Reply to
Sjouke Burry

I don't know why I'm bothering to respond to this troll, but....

It's not a question of simple resistance in ohms. Look up "breakdown voltage" for further information.

Bob M.

Reply to
Bob Myers

Around a million? Not several millions? Cloud to ground strikes can be several miles long and range into the hundreds of millions and billions of volts, and tens to hundreds of thousands of amps.

Lots of electrical texts have charts for dielectric strength. I doubt that one insulator will be right for all applications. Dielectric strength is specified in volts per mil, so even poor insulators, if thick enough, can stand off high voltages.

What was your idea? Surround something with an insulator to protect it from lightning? Surround what?

Lightening is a fast rise time pulse(s). The insulator, even if it withstands the strike, will likely couple enough energy to the "protected" device to cause damage

All the practical systems of lightening protection I'm aware of, deal with directing the strike away from something, or bleeding off the space charge before a discharge can occur in that area.

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Reply to
default

Ohhhh ! Not you again you brain dead nitwit.

Just try *thinking* about the stupidity of your question will you ?

Graham

Reply to
Eeyore

I would think a vacuum would do it.

Sometimes it's better to "go with the flow" and "re-route" the lightning, rather than attempt to block it.

Consider surrounding the device to be protected with a grounded conductor and forget about insulators.

Chuck

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Reply to
chuck

I thought that a vacuum had relatively weak (electrical) insulating properties, to say.. air for example?

Mark

Reply to
Mark Fortune

A hard vacuum is very good. The lowest breakdown is at some low pressure, a small fraction of atmospheric as I recall; after that point, better vacs are better insulators. A perfect vacuum is a perfect insulator, and the only limit is when the field strength gets so high that ions are ripped out of any metal electrodes that are present, at vaguely around 1e8 v/m. Tomographic atom probes use this effect; see Imago.com.

An interesting effect is secondary emission in metallic surfaces, which can become a positive feedback effect for AC. See "Farnsworth multipactor."

John

Reply to
John Larkin

Probably in the billions of volts. I was just guessing.

Okay

I was just curious

Anything.

Are you referring to damage caused by the EM waves emitted by the pulse?

True.

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Reply to
Radium

Doesn't a vacuum has very *low* resistance? Or are you referring to the stuff around the vacuum? What is the insulation covering the vacuum made of?

Yes.

True.

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Reply to
Radium

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I don\'t think so. Stick your ohmmeter probes into a vacuum and
you\'ll read a higher resistance than air, even.
Reply to
John Fields

Insulators are dielectrics they will transfer energy just like a capacitor charging. Fast rise time is similar to high frequency - large high frequency component in the wave form. One plate is the ionized gases surrounding the insulator, the other the protected device.

And as you point out EMP

I was on a beach stringing a wire from my bike to a tent to run a reading light. A strike that was easily 10 miles away induced enough voltage in my wire to give me a shock.

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Reply to
default

An ohmeter I would expect to read infinate resistance, but at the voltages we're talking about (ie involving lightning) isnt the breakdown voltage much lower than air?

Reply to
Mark Fortune

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Not if it\'s a hard vacuum.
Reply to
John Fields

It would be damn hard to manufacture vacuum tubes and CRTs if you were right.

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Reply to
Michael A. Terrell

8000 miles of earth.
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Reply to
Homer J Simpson

Vacuum can't break down; there's nothing to conduct with.

Electrodes in a vacuum can break down, namely emit electrons or ions from their surfaces, but that's different.

John

Reply to
John Larkin

Once again, with feeling: do not confuse "insulating properties" with resistance ALONE. Think "breakdown voltage," which is something else altogether.

Bob M.

Reply to
Bob Myers

A vacuum has an extremely HIGH resistance, as long as you are talking about conduction in the normal sense. Again, go look up "breakdown voltage" and learn something for a change. Up to the breakdown point, I think you'll find that the I vs. V curve for a reasonable amount of separation in a vacuum is pretty damned flat...

Bob M.

Reply to
Bob Myers

Damn, John, now you're REALLY going to send Radium, et al, down a rathole.....

I'll get the popcorn...

Bob M.

Reply to
Bob Myers

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