Why don't electrons leave a negatively charged metal in air?

[ZapperZ]

ZapperZ, I want your opinion on this reasoning:


The resistance of vacuum is zero, because if a particle has some momentum and is traveling in vacuum, it keeps the same momentum. Right?

The resistance to THAT particle is zero. But the resistance of a vacuum isn't zero. If it is, then air capacitors would not work over all range of potential difference. You would short out all vacuum, and not only that, particle accelerators would not work.

If you have two separate metal objects, and vacuum in between, and try to get current carried out from one object to another, you will measure very high resistance. However, this does not mean that the resistance of the vacuum would be great, but that the resistance of the

metal + boundary of metal and vacuum + vacuum + boundary of metal and vacuum + metal

is great, and the resistance arises in the boundaries due to the mirror charge effect. Right?

Depends on what you mean by great, because you could also say that an "open circuit" or an "open switch" isn't fully "open". By definition, an open circuit conducts no current. If not, then most of our electrical circuits are wrong, because what's to prevent someone from "pretending" that there's a small current going in all directions through air?

It is an experimental fact, that vacuum is better insulator than air. That means, that the current will break through more easily, if there is air in between? Right?

Of course, I'm hoping that we're dealing with the classical vacuum and not impose any exotic "vacuum fluctuation". So yes, this is correct. Even in the so-called "vacuum breakdown", it requires the presence of neutral gas atoms/molecules.

All this together implies, that the air alone is not an insulator at all. Right?

It is a good insulator, not perfect. But then again, what is perfect? Again, simply by showing that an air capacitor can be maintained is sufficient to show that air is an electrical insulator over a range of potential. The same can be said about ANY insulator.

If the question is "What makes air such a good insulator, when it's just gases, relatively few molecules moving all over the place bouncing on each other, how can this be a good insulator?", the answer is, that actually the air is not an insulator?

Because the molecules that make up air is neutral, and requires a certain amount of energy (ionization potential) to ionize it first before it can conductor electrical charges.

Zz.

 

[ZapperZ]

When a mentor distorts your words in such an obvious way (maybe because he forgot about Tesla coils), what are you supposed to do?

If you hear something that you know to be untrue (eg that mutual repulsion has nothing to do with pins), are you supposed to pretend it's true because you're the OP who's asking?

You still have failed to prove a single reference source to support your model. Show me the source that gives you the evidence that this is "true".

I can claim that mine is "true" because I can show you several different published papers on the model that I had described. Furthermore, I also do EXPERIMENT on this! I have a 1/2 cell RF cavity that in can put in up to 120 MV/m and with a bunch of diagnostics to capture the breakdown dynamics.

The fact remains that without any published support, what you had done here simply your own personal theory, which is in violation of our Guidelines. It is even more baffling that you are expecting someone to explain something that you just made up.

Zz.

 

[Ulysees]

> You still have failed to prove a single reference source to support your model. Show me the source that gives you the evidence that this is "true".

And what model are you referring to now? Many things have been mentioned. Are you referring to the following statement?

> something that you know to be untrue (eg that mutual repulsion has nothing to do with pins)

If you are referring to this, then I'm copy-pasting the meaning of it, mentioned above:

> Extra charge goes to the surface [of any conducting object] because of mutual repulsion. Of all the parts of an arbitrary [closed] surface, which ones are further from the "middle"? The bulges and the pins are, and that's where extra charge goes more. But when there's too much in a bulge, it stops more electrons from coming. It's just equilibrium.

This is from a diagram at High School. I'm sure you can imagine it, maybe you've even seen it and read the High School explanation that goes with it, which is as shown above.

 

[ZapperZ]

> You still have failed to prove a single reference source to support your model. Show me the source that gives you the evidence that this is "true".

And what model are you referring to now? Many things have been mentioned. Are you referring to the following statement?

This model:

I'm familiar with lightning rods taking advantage of the mutual repulsion of charges to shoot off a corona discharge off the sharp end and start a thunder, but why doesn't corona discharge happen to all charged metals?

Where is there such a model for "lightning rods taking advantage of mutual repulsion of charges to shoot off a corona discharge off the sharp tip end"?

The model that I described has no such thing. The 2 papers that I cited has no such thing. So can you please cite the paper that would support such "mutual repulsion of charges" that causes such a discharge?

Zz.

 

[Ulysees]

"lightning rods taking advantage of mutual repulsion of charges to shoot off a corona discharge off the sharp tip end"?

OK here it is. It is also from High School physics:

Here's what the book says more or less. The sharp end of the lightning rod results in a high concentration of charge when charge appears in the ground. This is because, as in any conductor, charges repel each other to the sharper ends.

If the charge accumulation is strong, it ionises the air, which therefore enables more charge to exit the rod from the sharp end as it is atracted to the ionised air. Eventually this results in a thunder. Therefore a thunder develops in an upward direction.

 

[Ulysees]

Ok now? No repulsion, no accumulation. No accumulation, no lighting rod, thunders can start from the roof.

 

[ZapperZ]

"lightning rods taking advantage of mutual repulsion of charges to shoot off a corona discharge off the sharp tip end"?

OK here it is. It is also from High School physics:

Here's what the book says more or less. The sharp end of the lightning rod results in a high concentration of charge when charge appears in the ground. This is because, as in any conductor, charges repel each other to the sharper ends.

If the charge accumulation is strong, it ionises the air, which therefore enables more charge to exit the rod from the sharp end as it is atracted to the ionised air. Eventually this results in a thunder. Therefore a thunder develops in an upward direction.

Holy Cow! You're arguing with me using high school text that appears to have something that is internally inconsistent?

I should have given up a long time ago when I said it first time.

Zz.

 

[Ulysees]

Just admit it, mutual repulsion to the sharp ends is critical.

 

[ZapperZ]

Just admit it, mutual repulsion to the sharp ends is critical.

You should quote the author, title, and publisher of this "book", because someone (maybe me) needs to write to the publisher for teaching high school kids such garbage.

Zz.

 

[Ulysees]

Will you apologise for ignoring the "negatively charged" in the title, because you forgot about the following?

View attachment 12613

 

[Ulysees]

It's not a copy I have here, it's what it says more or less.

 

[Ulysees]

You should justify your statements, like we all do.

Proof is more important than authority. Otherwise we'd still be in Newton's era. Or should I say the middle ages.

 

[ZapperZ]

Will you apologise for ignoring the "negatively charged" in the title, because you forgot about the following?

View attachment 12613

.. and how is this relevant to the standard lightning rod? Do you see a belt attached to a lightning rod that supplies charges to the the rod the SAME way as the van de graaf dome? Again, you are mistaking two different phenomena as being the same!

And don't tell me that you actually pay this close attention to such pictures! Really now! If you are ever at Argonne during its open house, try and come visit our Van de Graaf facility. It's WAY bigger than that, and it can accelerate electrons up to 3 MeV!

You should justify your statements, like we all do.

Proof is more important than authority. Otherwise we'd still be in Newton's era. Or should I say the middle ages.

I did! I cited to papers in peer-review publications! I don't think you know what that means, though. You cited something off some "high school text". Which do you think has more of a validity in terms of completeness and accuracy? You also seem to forget that I do experiments in this area of study. I don't just read it.

I see this thread as going nowhere, considering your inability to comprehend what I have mentioned, and your refusal to even learn what has been said. So it is done.

Edit: If someone has the author and publisher of this "textbook" that has that silly quote, please PM me with the info. The least I can do is to stop this faulty info from being perpetuated.

Zz.