Which material has high enough ohmage to resist lightning?

Unless the electrodes are made of Mexican cobalt. ;-)

Tim

Damn! It was for the rats, so they would follow Radium into the hole.

heat the negatively charged end and it has a relatively low resistance. (see thermionic tube)

when cold untill you get the voltage high enouh to extend the electron orbitals across the gap or to strip ions off one electrode it's an insulator.

typically some sort of glass, a cheap, relatively good, insulator, only problem is how brittle it is.

Bye. Jasen

Ummm...which is the "negatively charged end" of a vacuum?

Bob M.

Interesting, how some materials lose resistance when cooled while others lose resistance when heated.

What is the breakdown voltage of the glass?

Breakdown voltage for air is about 75 kvolts per inch. For glass, it could be as high as 3,000 kv per inch. But this becomes irrelevant. Question was about voltages found in lightning. Other factors change those numbers. Three miles of air - a best insulator - could not stop lightning. We don't even try. We solve the problem by diverting - shunting. Diversion means that voltage does not exist. Dominant factor in lightning is not its voltage. Lightning is a current source

- an electrical concept necessary to better understand the problem.

Furthermore, you are asking about resistance - DC electricity. Lightning is an AC source. Therefore ask about both resistance AND reactance.

To better answer your question, provide what it is you are trying to understand. Your question about insulating from voltages such as lightning assumes lightning can be stopped - when even three miles of air could not insulate sufficiently.

Some sources describe lightning as being neither AC nor DC but *much* closer to DC than AC. Others state that lightning is AC. Who should I beleive?

Preferably infinite. LOL

It's DC but it's an impulse.

True. AFAIK, a smooth sine-wave current [DC or AC] can only be produced artificially. Of course I could be wrong.

Think of a freight train hitting a cement wall. It mostly goes in one direction but there's a lot more going on.

Good idea. I remember reading about a small (relatively speaking) Tesla coil that was supposed to be able to produce a few million volts. It was in a large horizontal oil bath.

One of the benefits of oil - gets in all the tight spaces and prevents corona which leads to insulation failure and lowers breakdown voltage.

Radium needs to build a few Tesla coils for an appreciation of insulators.

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the end with the negative charge attached.

A basic engineering and a basic mathematical concept: an impulse is a sum of AC waveforms at many frequencies. The shorter that impulse, then the more AC frequencies are in that impulse.

The term DC impulse is a contradiction or oxymoron. Either it is an impulse - a sum of many frequencies - or it is DC.

For example, to determine the frequency response of a circuit, we apply an ideal impulse. That ideal impulse applies every frequency to the circuit. Circuit output is then captured to learn how well each frequency transverses the circuit.

Many AC frequencies > Homer J Simps>> It's DC but it's an impulse.

AC -- by definition -- requires that the current reverse its flow.

A changing voltage isn't necessarily AC. Its only AC if the current changes direction. Otherwise its still DC.

A DC impulse is a impulse that -- for a relatively short duration -- increases its strength of flow toward one direction and then stops, without reversing its flow.

An AC impulse does similar but instead of stopping, it will increase its strength of flow in the opposite direction and then stop at zero volts.