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Re: Something Different
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Ok so you are saying car systems put out about 100KV??
air has a breakdown of around 20KV per inch of airgap.

So you are trying to tell me your car ignition has 12.5cm
sparks flying out the end of a plug lead??.

That should be pretty spectacular....

Re: Something Different

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They're out there, think racing engines. 50KV and higher is not unusual.

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You're trying to ignite a mixture of air and fuel, not just jump an air gap.
You need a healthy fat spark for that.

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Nope, small gap, fat spark.

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Especially when you get bitten.



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Yep, you can also measure the resistance of those resistors. Have fun
measuring the resistance of wood using the same method though.




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Prove it or shut up about it.




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 From the Wikipedia definition for dielectric breakdown:
http://en.wikipedia.org/wiki/Dielectric_strength

"The maximum electric field strength that it can withstand intrinsically
without breaking down, i.e., without experiencing failure of its
insulating properties."


IOW when it's insulating properties fail it becomes a CONDUCTOR.


 From the Werner PDF file on fibreglass ladders for the electrical
industry, some tests on the CONDUCTIVITY of wood and fibreglass
ladders:
http://www.wernerladder.com/catalog/files/rc81.pdf

2. DC leakage current(in uA) as related to conditioning for 10"
electrode spacing, 80% relative humidity conditioned at 22 C.

Applied Voltage
Time         Wood     Fiberglass     Wood     Fiberglass
As Received     90 KV     90 KV         7.0     1.0
24 hours     50 KV     90 KV         48.0     1.4
48 hours     50 KV     90 KV         67.0     1.9
72 hours     50 KV     90 KV         120.0     2.4


As you can see at 50KV wood begins to CONDUCT, now what part of this
concept don't you understand?. Are you aware that lightning is higher
in voltage than 50KV?.


Re: Something Different


Mark Harriss committed to the eternal aether...:

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The voltage in a laptop computer isn't

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Pity what was being discussed was lightning, fuckwit.



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You're a parody of yourself.



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Rod Speed committed to the eternal aether...:

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Take a look at the OP, it's clearly about a timber laptop case

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Yes... but, this is all in reply to the real andy's assertion that
any type of dry wood will not conduct lightning.

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Completely irrelevant to what the thread diverged to, LIGHTNING,
and what we chose to comment on with LIGHTNING.

Do TRY to keep up.



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I *know* wood or any insulator conducts if the voltage is high enough, I
wanted to see the evidence from that lazy bullshit artist Rod.

And 50KV is pretty low, really.



Conduction at high voltage: rubber


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I once made the mistake of trying to use once inch dia. black rubber
tubing to insulate some conductors with 47KV on them: after a few
seconds it begans to smoke heavily and start to pop: I assume the
rubber had carbon black added to colour it. The stuff was more of a
resistor than an insulator at those voltages.

Apparently hot glass is conductive from the sodium ions in it as well
: heat some up till it's red and then microwave it to see a lightshow.

Re: Conduction at high voltage: rubber


Mark Harriss committed to the eternal aether...:

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Maybe the wires got hot and burnt the rubber?

Re: Conduction at high voltage: rubber


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The wires were attached to the ends of the 60cm length of rubber tube
which was used to space the wires out as they were not rated for HV.
The voltage was able to breakdown the 1000V rated insulation and cause
enough flow across the rubber to make it start crackling and popping
with lots of smoke.

Re: Conduction at high voltage: rubber



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Rubber conducts rather well if it has a high carbon content. Try putting a
multimeter across a rubber tyre and measure the resistance.



Re: Conduction at high voltage: rubber


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Unlikely with that sort of voltage on them.

The best insulation for that sort of voltage
is one of the thicker coaxs like RG8



Re: Conduction at high voltage: rubber


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I'm on the lookout for x-ray cable if anyone has some
lying around the place.

Re: Conduction at high voltage: rubber


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RG8 is fine, I ran quite a bit more than 50KV thru that fine.




Re: Conduction at high voltage: rubber


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I bought about 20 metres of RG8 on a cable drum from the
recycle shop for $5....then gave it to a mate for free,
it amazing what eventually would come in handy.

Was the braid earthed at that voltage?

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