AC flowing through a cap. What actually happens?

[killivolt]

I stood corrected by Mr,Al. "Should vs Shouldn't" Typo.

 

[MrAl]

Hello again Electrician,

Im sorry i forgot you came in a little later in the discussion. All along i have been not calling "displacement current" real current (ie conduction current).

What a lot of theory tells us is that current creates a magnetic field and a magnetic field creates a current, so there is a sort of recursive relationship there that seems inseparable. And this is what theory would have us believe.

The difference between what you are calling "displacement current" and what i am calling "displacement current" is that you are referring to theory, something we already know, and then simply repeating, and saying that you can measure it through inference. Like it or not, when you measure the field you are inferring from that field. (I suspect you realize this already though). What you are saying basically is that there is such a thing as displacement current and we can infer its presence from a measurement of the field. The only problem with that is it still doesnt tell us if there is charge transferred or not.
What you said about charge not existing in space means that there can not be charge transferred, and that's what i was telling Brownout, but Brownout disagrees. So i guess what we are trying to do is determine for sure if there is any charge transferred or not.

What we need is a second approach to this problem. I believe that second approach will include the conservation of charge, and this may lead to a totally unexpected result because as i was saying before, when we look at the charge on both plates in the static case we see exactly what we expected, but in the dynamic case the corrected Ampere term comes in. Now if the displacement current is somehow supposed to make the conservation of charge work out, then it might be nice to look into what the displacement current really is, from a physical standpoint.


But anyway, it would be nice to have a way to measure the so called 'displacement current' directly rather than infer its existence from the field.

 

[BrownOut]

@The Electrician: Thanks for your excellent presentation on displacement current a couple pages back. I'm just getting back to reading this thread after the weekend. It's refreshing to see a knowledgeable person discussing Physics using the appropriate equations and identifies, and correctly deriving the results. I completely agree with 100% of what you've written. Especially the correct conclusion that the professor and others are ambiguious due to sloppy use of the terms current, conduction current, displacment current, etc. That's why I posted the link to Shaum's Outline on dispalcement currrent so that readers can understand the differences. And it was good to see you validate that current has two constituants. I've been saying that all along, to deaf ears. I also agree the whole thing would be less confusing if not for the very minor ether point. Fact is, the displacement term is current, but because some have trouble thinking about current flowing in a vacuum ( still do appearently ) the 'ether' was unfortuantely discussed, giving a way for distractors to question Maxwell's results.

A few other points: Yes, the professor did stumble badly trying to articulate what current actually passes through the capacitor, but in the end, clearly stated that displacement current flows through the cap ( I watched all the videos ) I can see other's are still in denial about this. But he said it, unambiguously.

The professor may have failed to measure the displacement current between the capacitor plates, but M. R. Van Cauwenberghe sucessfully did measure the same in 1929, and thus validated Maxwell. I've asked many times how a mathimatical artifice, pretend current, virutal current, etc can produce a correct masurement, but have yet to get an answer.

No redifinition of current needs to be done to state that current flows through the capacitor, as that was done 150 years ago, and has only been validated, never disproved or improved upon.

I agree with EricGibbs. I pity the poor noobie who adopts Ratchet's pseudo science. He will either look like an idiot or a fool when he goes to his job, or an interview. That's why I feel so compelled to weigh in whenever I see that tripe being posted.

There is no need for a more quantitive discussion about displacement current. Maxwell's work is alread quantitive. Those arguing against Maxwell need to do some quantitive analysis however.

Displacement current is not conduction current. Yes, it is current nevertheless.

The Electrician's post #273 deserves a re-read from anyone who really wants to know about displacement current, and if it's real or not. He is not just repeating something already known. He understands the issue of this current, and is very capable of explaining it in plain terms, better than some of the professors who's videos have been linked on here.

Ok, there was more that I wanted to say, but so much has transpired since I last visited, I just wans't able to remember everything.

 

[MrAl]

Hello Brownout,

"The professor may have failed to measure the displacement current between the capacitor plates, but M. R. Van Cauwenerghe sucessfully did measure the same in 1929, and thus validated Maxwell. I've asked many times how a mathimatical artifice, pretend current, virutal current, etc can produce a correct masurement, but have yet to get an answer."

Well that's very encouraging. What did he use to measure and how did he measure this seemingly illusive current?

 

[BrownOut]

What elusive current? It's well known, well documented and has already been measured. There is nothing elusive about it.

The results of the first measurement of displacement current were published in "Experimental verification of electromagnetic equivalence between Maxwell dispalcement current and conduction currrent" ( Notice that he is talking about two different currents, displacement and conduction, a distinction little known to Maxwell's distractors ) in Journal de Physique, Nov 8, 1929, p. 303. Anyway, it appears he used a soliniod attached to a resistor and measured the heat dissapated. I'm looking for better details. But the simple fact remains that id was measured 80 years ago, so one person's failure dosne't change the fact that it has already been measured and confirmed.

 

[MrAl]

What elusive current? It's well known, well documented and has already been measured. There is nothing elusive about it.

The results of the first measurement of displacement current were published in "Experimental verification of electromagnetic equivalence between Maxwell dispalcement current and conduction currrent" ( Notice that he is talking about two different currents, displacement and conduction, a distinction little known to Maxwell's distractors ) in Journal de Physique, Nov 8, 1929, p. 303. Anyway, it appears he used a soliniod attached to a resistor and measured the heat dissapated. I'm looking for better details. But the simple fact remains that id was measured 80 years ago, so one person's failure dosne't change the fact that it has already been measured and confirmed.

Hello Brownout,


Thanks for informing me, but why are you telling me about an elusive current? I never once mentioned anything about an elusive current.

I am really interested in seeing the experiment, and i am sure Professor Viken will be too. So far i have to say that it sounds like the same ol' story though, where we look for a field influence and infer an equivalent current. See if i was allowed to put metal into the region between the plates i could confirm this tomorrow morning
Of course I cant know for sure what he did until i see the experiment setup and procedure and results. It does certainly sound interesting for sure.
Is there any online source for this paper?

 

[The Electrician]

...it might be nice to look into what the displacement current really is, from a physical standpoint.

But anyway, it would be nice to have a way to measure the so called 'displacement current' directly rather than infer its existence from the field.

What "displacement current" is from a physical standpoint, is the time rate of change of the electric flux.

How could we possibly measure the "displacement current" without measuring the field (thereby inferring its existence?) since it is just the derivative of a field? There aren't any particles to measure, only a field.

If the "displacement current" is a flow of particles perhaps we might find a way to measure them without measuring fields, but failing to find particles only provides evidence of the truth of the fields theory, and I would certainly hope that we would fail to find particles in the vacuum of a vacuum capacitor (as long as we don't have thermionic emission from a red hot capacitor plate).

Don't most of the standard methods of measuring "conduction current" rely on the effects of fields produced by the flow of the charge carriers? Otherwise, wouldn't we have to utilize some way of actually counting the carriers go by?

 

[Mr RB]

...
Zero place in electronics? You have to realize what you just said. You just said that this thread says nothing more about a capacitor then the external view, which if you read back, i was debating with Ratchit about, and i took the side you are taking now. But also if you read back, you'll see that i digressed in order to get more in line with what the original poster asked. ...

I apologise Mr Al, there was no intention to belittle your argument of what happens inside a cap, and I have read your argument and largely agree with your points (although the horsefeathers part left me a bit cold).

... The original poster wants to know what "really" happens.
Now you want to define what "really" happens as what happens outside the cap, while the main reason most of the people are talking here is to figure out what happens inside the cap. We already know what happens outside the cap, it's time to move on to what happens inside the cap.

Sure, just to clarify my argument was more a "side argument", specifically with trying to ensure respect for the necessary terms current and through. Now that seems to have been settled (and possibly covered a bit too much) I don't mind joining the capacitor internals argument.

The trouble is I not exactly sure what the argument is. Can you explain in the simplest concepts? Is the argument about whether an electron travels through the cap from plate A to plate B? Or is it more about the best terms to use?

 

[BrownOut]

Hello Brownout,


Thanks for informing me, but why are you telling me about an elusive current? I never once mentioned anything about an elusive current.

Ok, illusive then, which it ain't either.

I am really interested in seeing the experiment, and i am sure Professor Viken will be too. So far i have to say that it sounds like the same ol' story though, where we look for a field influence and infer an equivalent current.

That's how current has been measured for over a century. If you throw this out, then you have to throw out every current measurement made for the last 100 years or so.

Of course I cant know for sure what he did until i see the experiment setup and procedure and results. It does certainly sound interesting for sure.
Is there any online source for this paper?

I've been searching. I'd like to see it too. For now we know that displacement current was measured, and the results were published in a respected, peer reviewd journal of physics.

 

[BrownOut]

Mr RB,

Is the argument about whether an electron travels through the cap from plate A to plate B? Or is it more about the best terms to use?

I know this question was for someone else, but I wanted to put in my 2c. Different people are arguing different points. Despite what others will say about the claims being made, myself, ljcox and a few others have not make any claim that electrons pass through the dielectric of a capacitor. We've argued that Amphere-Maxwell defines current, and that current has two terms, a conduction term and a displacement term. Wether or not that is significant to circuit analysis isn't our concern. We are only supporting the scientific foundation of electro-magnitism.

 

[killivolt]

Can you explain in the simplest concepts? Is the argument about whether an electron travels through the cap from plate A to plate B? Or is it more about the best terms to use?

Speaking of a single electron theory. Mr.Al did speak briefly but, we did not continue along that course. Forgive me, Mr.Al if I am off base. I began to remember the Penning Trap I read about 4yrs ago, most likely you guy's already know about it. I am a Humble Hobbyist.

With my limited understanding it may not apply but, might seed something in someone's mind. Again, I'm apologizing now, if I am off base and cause you to read something of no value.

This is a result of such an experiment.

Geonium atom - Wikipedia, the free encyclopedia

Single Electron Traped in a strong Magnetic Field un-able to do more than to oscillate if you will in a rotational movement. If a single electron or many electrons are not permitted to pass maybe, (Only in my Mind) result in a release of photons. If a photon is able to be release it may be collected on plate B in a photo electric composition.

A passive ejection happens and the electron is able to produce an low energy polarization that attracts energy build up on Plate A as it rotates back through to it's primary position only to be rejected again yet able to transfer allowing it to remain at the original state of energy. That single electron or more, could therefor repeat this process at an alarming rate, while being proportional to a time element.

I think I'm on drugs but, it could just be my last Asthma attack this morning.

 

[Ratchit]

MrAl,

Finding an experiment to prove/disprove "displacement current" proved to be remarkably easy.

The following link purports to describe the existence of displacement current

https://www.electro-tech-online.com/custompdfs/2011/03/p1065-1073-2.pdf

The follow link says it isn't so.

https://www.electro-tech-online.com/custompdfs/2011/03/qingping2-6.pdf

Take your choice.

Ratch

 

[BrownOut]

MrAl,

Finding an experiment to prove/disprove "displacement current" proved to be remarkably easy.

Izzat so?

The following link purports to describe the existence of displacement current
https://www.electro-tech-online.com/custompdfs/2011/03/p1065-1073.pdf

The title is "A Direct Experimental Proof of Displacement Current" Odd title for an experiment that purports to disprove something, when it says it proves it, don't you think? In fact, they report a measurable displacement current, and validate Maxwell. Looks like you torpedoed your own position

The follow link says it isn't so.

https://www.electro-tech-online.com/custompdfs/2011/03/qingping2.pdf

Saying something isn't so is not proof.

Take your choice.

Ok, I choose the one that proved displacement current.

 

[MrAl]

Hello again,


The Electrician:
Well see a while back we were talking about units, that the Ampere-Maxwell displacment term
can be easily shown to contain units of Amperes multiplied by the constant u0, and this is
what lead some to say that it was a true current, just because it was in amps.
Thus i began to argue that it must be something other than a true current, because we know
that electrical current is a flow of charge. That lead us to argue about if it was charge
or not, which also invoked the charge conservation law.
So i was thinking if we could measure it without detecting the field, then it must be a
true flow of charge. If we have to detect the field, then we cant tell, at least for
sure anyway.
I was coming to the same conclusion as you are however, that this illusive 'current' may
not be measureable in the way we normally measure current because it is simply not the
same as conduction current.

About the other standard methods of measuring current:
Well, im sure you know that we can measure current by sampling the electron flow with good
ol' Ohms Law, which gives us a voltage proportional to current. But RMS current would be
measured by detecting the heat generated in the resistor.
Of course detecting the field is what the Hall Effect sensor is all about, so that is another
option. We sample the field and make the necessary calculations.
Apparently though if we want to pick apart these 'theories' we would note that we have to
make assumptions there too. Abstractions again.

Perhaps the only question then is just how a field can cause a directed behavior in a non
conductor in the same way that a true conduction current in a conductor behaves. Normally we have
a field generating a current in the wire, and that's good enough. But here we have a field creating
an 'apparent' current (or 'virtual' current as you mentioned), but we dont really know what that really is.
We could look at the real current as being generated through the virtual photons of the field,
that the field acts on the charges and causes them to move, and this is what we measure as conduction
current. We then automatically associate the field with the conduction current.
But in the case of the vacuum, we are assuming there are no real charges to move, so there is
effectively nothing to move.
Ok, so now we have two choices:
1. The B field acts on some other kind of particle and a 'flow' of these particles makes up this new kind of current.
2. The B field is just the electric field viewed in a different perspective, but then nothing really 'flows'.
I tend to believe (2) but then it's hard to call the displacement current a 'current', so that's how it
seems that in the Ampere-Maxwell the e0*dPhi/dt term although expressed in Amperes, is not really a current,
it's just the B field showing off its electric field. Now an electric field is 'across' an object, while
a current is considered to be 'through' an object. This is fairly basic. So if we just have something
that is acting 'across' an element, we dont have current unless we pretend we do, or else real charge
is flowing.


MrRB:
Ok sure.
We sort of have a couple different arguments going here, i think that is part of the problem. We are
arguing about:
1. What this 'displacement current' really is.
2. If it really can be called a 'current' at all.

For #1, it appears that what is being called a displacement 'current' is actually just a change in a
field flux, but multiplying that change by the permittivity of free space puts it in units of Amperes.
Thus, this leads people to call it a 'current'.
The other side says that the change in field flux only creates a B field, and that the displacement current
is not a real current by any scope of the word.

For #2, it's almost the same as #1, because before we know what to call it we have to know what it really is.
It has been traditionally called the 'displacement current', because it works out to units of Amperes. But
we know that amps is a flow of charge carriers. So the question becomes: is it really a flow of charge
carriers or not? If we want to say that it is we'd have to figure out how it can get through the
vacuum of space.

We calculate the displacement current using the second term of the Ampere-Maxwell, and we calculate a
general current through a resistor using Ohms Law. So you see we know how to 'calculate' it, we just
dont know exactly what it is.

My view is that although it can be expressed in units of Amperes, that doesnt mean it has to be a true
current. It can simply be the changing field converted to Amperes for convenience, and also to
satisfy the conservation of charge law.

Brownout:
"Ok, illusive then, which it ain't either."
Yeah, that's why this thread is so short.

"That's how current has been measured for over a century. If you throw this out, then you have to throw out every current measurement made for the last 100 years or so."
Most currents are measured as being through a wire, but in the vacuum cap we have no conducting medium. That makes it harder to deal with right?

"I've been searching. I'd like to see it too. For now we know that displacement current was measured, and the results were published in a respected, peer reviewd journal of physics. "
Dont forget to mention that it was in the year 1929.
But maybe even more importantly, what was it that was actually measured...was it a flow of charge, some other particle, or the field? If you come back and say "the displacement current" then you wont have cleared this up at all.
That was a good find on your part in any case, and will be nice to read someday.

killivolt:
Well that is interesting, but unfortunately Radio Shack doesnt carry them and Digikey is on backorder
On the more serious side, i dont have the facilities to make one of those and im not sure if we could
use it or not. I'd have to read up more on those devices.

 

[MrAl]

Izzat so?



The title is "A Direct Experimental Proof of Displacement Current" Odd title for an experiment that purports to disprove something, when it says it proves it, don't you think? In fact, they report a measurable displacement current, and validate Maxwell. Looks like you torpedoed your own position




Saying something isn't so is not proof.



Ok, I choose the one that proved displacement current.

Brownout,

I think you may need to slow down just a bit when you read the other peoples posts. You seem to be misunderstanding some basic words and meanings. I think it is just that you are in a hurry, that's all, not that you would not understand it if you took your time. I am guessing you are heavily involved with something else too while reading here.

 

[BrownOut]

Yeah, that's why this thread is so short.

And that proves, what?

Most currents are measured as being through a wire, but in the vacuum cap we have no conducting medium

All current is measured by examining it's B or H field.

Dont forget to mention that it was in the year 1929.

And has since never been disproved.

But maybe even more importantly, what was it that was actully measured...was it a flow of charge, some other particle, or the field? If you come back and say "the displacement current" then you wont have cleared this
up.

According to every reference I've seen, it's displacement current. If you have an experiment that refutes this, then publish it.

 

[MrAl]

MrAl,

Finding an experiment to prove/disprove "displacement current" proved to be remarkably easy.

The following link purports to describe the existence of displacement current

https://www.electro-tech-online.com/custompdfs/2011/03/p1065-1073-1.pdf

The follow link says it isn't so.

https://www.electro-tech-online.com/custompdfs/2011/03/qingping2-1.pdf

Take your choice.

Ratch

Hello Ratch,

Those two look interesting. I may have to spend more time with them however.
I did take a quick look, and it seems that this topic is just getting more and more complicated as time goes on. That second reference doesnt seem to be supported with any real experimental evidence, i hate to say, but i have seen other things on the web now that purport to disqualify not only displacement current, but also as that second ref says, to disqualify even the existence of a B field between the plates of the vac cap. They have some compelling experiments, but unfortunately none of them describe the setup and procedure. Also, many of them require expensive equipment which i dont have access to at the moment.
All i can do at the moment is give all this some more thought, and thought is a lot cheaper than equipment.

 

[BrownOut]

Brownout,

I think you may need to slow down just a bit when you read the other peoples posts. You seem to be misunderstanding some basic words and meanings. I think it is just that you are in a hurry, that's all, not that you would not understand it if you took your time. I am guessing you are heavily involved with something else too while reading here.

That might be good advise, if it haden't come from a member who has repeatedly misquoted me as arguing that charge is transfered through space, a claim I never made. ie:

Originally Posted by MrAl What you said about charge not existing in space means that there can not be charge transferred, and that's what i was telling Brownout, but Brownout disagrees.

 

[MrAl]

Brownout:

Oh i see, so if for example, *i* misquoted you one (or even more) times then it's not good advice, but if *i* didnt misquote you, then it's good advice. Well then maybe you can find someone who never once (God forbid) misquoted you and ask them to confirm or deny
You'll thank me later

Seriously though, i said that for your benefit as i thought it would help, that's all. It's not the same as saying you are dumb or anything like that.

 

[BrownOut]

Well maybe once would just be a misake, but to still not know what I've been arguing for all these days seems careless to me. That might also help expalin the length of the thread you mentioned earlier.