AC flowing through a cap. What actually happens?

[BrownOut]

Well, then where does the charge come from for this current?

There is no charge. I've said that all along.

If the B field is going to move any charge, it's got to get it from somewhere and the dielectric can not supply any electrons.

The B field exists everywhere in the region. It might move charge or it might not.

You're saying that the displacement current is the same as current

No. I said displacement current is current. ( Not "the same as..." )

and then you say that you can have BOTH displacement current AND regular current in the same wire.

No. I said they both induce a magnetic field around the same wire.

The problem is that you can not sum the two and get zero

No. I clearly said the magnetic field can be zero, but neither current needs to be zero.

I=0
but you're saying that
I+Id=0
yet your saying that
I=0 AND Id>0.
If Id>0 then
I+Id>0 when I=0.

Can't comment on things I never said.

In other words, if you measure 0 amps with the ammeter then you can not say that there is a displacement current that exists yet is not going to be measured, and still say that the displacement current is the same as regular current.

Except I didn't say displacement current is the same as regular current. In fact, I ( and the professor ) said displacement current is in addition to regular current.

You're saying that the displacement current is real current but then when we measure 0 amps you're saying that although it exists we cant measure it. If we cant measure it like real current then it's not real current.

It can be measured. A deflection coil meter that works only on conduction current might read 0amps, while say a current transformer, which works by measuring the magnetic field, can read non-zero.

Sorry if I'm beginning to spam the thread, but I am enjoying the discussion. My favorite thing about Physics is when a result is something totally unexpeceted, and the student ( me ) has to streatch and expand his thinking to grasp it.

 

[MrAl]

Hello again,

Maybe i misunderstood you then. I thought you either said or implied that the displacement current was the movement of charge, because i cant see how you can say that the displacement current is the same as (or actually is) current if you dont also say it is the movement of charge. If we are to say that the disp current Id is the same as the 'regular' current I, then we dont need to add to Ampere's original equation because the current itself would be the only domain and we'd be done. There's something else there, as in:
y=fa(i)
but that doesnt work, so we have to add something:
y=fa(i)+fb(e)
(something that depends not only on the current but also another quantity) in order to get the right result for the B field.
if current (i in above) was going to work as the domain to completely characterize the B field, then we would not need e (the electric flux).
BUT
if we want to simplify the way we think of it, we can say that the second part of that extended equation has units of amps * u0 and so it ACTS like the current. It ACTS like the current i, but it's not the current i because i is the current. We dont need a separate quantity if it is already the current.
There must be other examples like this in life, but this one is borderline particle physics so it's going to be a little different i think.

It doesnt matter however if you use an ammeter or a current transformer. A current transformer does not work by measuring the magnetic field, that's a field strength meter. A current transformer simply measures the current and turns it into a voltage so we can measure the voltage and equate to the current (im sure you know this). If the current is zero then the current that gets to the primary of the current transformer is zero also, but we dont have to complicate this experiment, so just use an ammeter and we dont have to specify what kind it is.

The thing that is unusual here is that if we measure i(t)=0 yet we still have something called the 'displacement current' then something is very different than when we have a small 'real' current creating a magnetic field. In other words, the magnetic field is there yet there is NO current flow. No current flow, none. The electric flux created the B field, not any current, yet we can pretend there is a current in order to explain the B field. That makes sense doesnt it? It makes it easier to think about, or supposedly so ha ha.

Yes this turned out to be an interesting discussion after all

 

[ljcox]

I suspect that when the physicists derive the "theory of everything", some of these concepts & terms will need to be revised.

For example, if string theory proves to be correct, then current may be shown to be a flow of strings.

I say this because the concept of current flow being the flow of charge carriers does not cover the concept of displacement current.

I believe this concept is derived from Maxwell's equations which, as I understand it, show that there is a displacement current through the dielectric of a capacitor even though there is no flow of charge carriers inside the dielectric: note that the dielectric could be a vacuum.

This raises the question in my mind - why do we need a conductor to carry current?

Obviously the charge carriers in the conductor play a role of some kind.

I'll leave the answers to these questions to minds that are greater than mine.

Since I started the Displacement Current part of the discussion, I thought it may be useful to re-read what I said.

In essence I said that when the "Theory of everything" is derived, we may find that it defines a wider definitiion of current than the flow of charge carriers concept.

 

[Ratchit]

ljcox,

In essence I said that when the "Theory of everything" is derived, we may find that it defines a wider definitiion of current than the flow of charge carriers concept.

Until the different branches of physics are all unified, a theory of everything is just a musing of the mind. In any case, it will not change what the definition of current (charge flow per time). If another quantity has to be defined, then that quantity will have a new name.

Ratch

 

[Ratchit]

MrAl,

The thing that is unusual here is that if we measure i(t)=0 yet we still have something called the 'displacement current' then something is very different than when we have a small 'real' current creating a magnetic field. In other words, the magnetic field is there yet there is NO current flow. No current flow, none. The electric flux created the B field, not any current, yet we can pretend there is a current in order to explain the B field. That makes sense doesnt it? It makes it easier to think about, or supposedly so ha ha.

Right you are Al. The way to obtain a magnetic field is to 1)use a permanent magnet, 2) run a current through a wire, and 3) change the electric field intensity and use the right hand rule to determine the magnetic flux density (B-field). In a capacitor with a changing voltage being applied, which results in a changing electric field intensity, the resulting B-field has a current equivalency (apparent current), but there is no real current. The prof showed the B-field and the equivalent "apparent current" mimics the real current with respect to amplitude and decay in a capacitor and resistor circuit with changing voltage.

Ratch

 

[ljcox]

ljcox,



Until the different branches of physics are all unified, a theory of everything is just a musing of the mind. In any case, it will not change what the definition of current (charge flow per time). Not necessarily. If another quantity has to be defined, then that quantity will have a new name.

Ratch

If you were standing by a river and saw leaves floating past you, if you did not know any better, you could refer to the leaves as "the current".

But we know that the leaves are really being driven by the moving water.

If it is current is slow and non turbulent, then the movement of the water is not visible.

So the only evidence of the current is the moving leaves.

My point is that the movement of charge carriers may be like that of the leaves, ie. they may be being driven by a yet to be discovered mechanism.

 

[Ratchit]

ljcox,

My point is that the movement of charge carriers may be like that of the leaves, ie. they may be being driven by a yet to be discovered mechanism.

I doubt it. Charge and current have been known and studied for decades now. There may be some esoteric things we don't know about as to how electrostatics relates to quantum mechanics and other branches of physics, but not this. Especially when a rational explanation is known and makes sense.

Ratch

 

[BrownOut]

Current transformers do measure current through the magnetic field. Look up noncontact current measurement. A wire runs through the CT,but does not make electrical contact. Thus, the displacement current is measurable. I don't know of any "pretend" quantity that can be measured.

I see everyone is still willing to parse the professor's lecture, but nobody is willing to deal with his conclusions, that displ. current flows through the capacitor.

 

[MrAl]

Hello again,

Brownout i thought you were one of those arguing that the current flows through the capacitor.

The displacement current shouldnt be called a current at all. Here's a better simple analogy...

We take a 2x4 piece of lumber from the lumber store about 1 meter long, and two 10 penny nailes. We drive the nails into the 2x4, one at each end, with the 2x4 laying on its side and the nails then sticking up vertically to form something like pegs. Now we take a string and tie one end around one of the nails near the head of the nail, and take the other end and tie that around the other nail so that the string is taught. The string now sits up above the 2x4 about an inch stretched across the two nails. Now we shine a light from above down on the string. What do we observe? A shadow appears on the 2x4 that looks like the string (about 1 meter long and fairly narrow).
Next, we take another 2x4 and two more nails and build another one of these little contraptions, except this time we leave out the string. Yes that's right, just a 2x4 with a nail at each end, and no string. Now again we shine the light down from above. Now what would happen if we saw another shadow, even though the string isnt there? A shadow 1 meter long and fairly narrow just like with the first 2x4 setup. What happens now?
Well obviously we would try to find out why this is happening because it seems so strange that we can have a shadow, yet no string in the second case. After years of trying we finally realize that we are not going to figure this out until physics advances further along, if we ever figure this out at all. So what to do? We realize that this problem would be much simpler if we just had a string there, so we hypothesize that there is a virtual string there and that explains the shadow entirely. This allows us to go on with our work and at least have a way to calculate the shadow.
So in the first case we had a real string, and in the second case we had a virtual string. In the first case everything worked out the way we think things should work out, but in the second case we have to use a little imagination. One thing is for sure though, in the first case there is a string, and in the second case there is no real string.

What this means then is that we cant really say that physically, current flows through a capacitor (except from the external view used to simplify the problem, which again is an imaginative experiment, ie the current flows in the leads so it flows through the device too). What we would have to specify is that the current flows into the capacitor an accumulates on the plates.
To say that current flows through a capacitor is like saying that an arrow can be shot through a sandbag, where the arrow enters one side and exits the other side. With the right force the arrow would stop and reside inside the bag with the tip sticking out one side and the tail sticking out the other side. If we were to compare this to current flow in the cap, it would mean the arrow hits a steel wall inside the bag and stops, and another arrow exits from the other side. The only way we can say it goes through is to use the particle identity clause that would say that both arrows loose identity, but even then we'd have to state how it accumulates at one side first.

Thus if we say "current flows through a capacitor" from the physical standpoint, we are implying that this is the coulomb flow, yet there's more to it than that.

Another little point:
If we have i(t)=0 but we still have B and we figure that as coming from the 'displacement current', then if this was a real current then we would not be able to observe i(t)=0, it would be i(t)=Id (Id being the displacement current). We already specified that we had i(t)=0 so we cant say that we have both i(t)=0 and i(t)=Id (some finite quantity), that's clearly a contradiction, unless we allow Id to be imaginary (imaginary as in 'not real', not as in the sqrt(-1)).

Note that the displacement current is being called a 'current' because the units work out to Amperes. However I is Q/t, so the question is, if the displacement current is a real current, where is the moving charge? It's working out to Amperes, so we need some charge to account for it, if it was real that is. The problem is there is no free to move charge in a dielectric, and no charge in a vacuum, so it can not be a true current. Funny thing is, i dont think we even need to conceptualize a displacement current, because the changing electric field is enough to describe what is happening completely.
In the virtual string and 2x4 example, if we could explain the shadow just by how the light itself behaved, we would no longer have to pretend there was a string there.

It's also common knowledge that current does not flow in a dielectric.

BTW a displacement current is also known by name as a virtual current.

 

[BrownOut]

We do observe i(t) = id. There is no contradiction, because the total current measured by observing the field is the sum of both currents. The error was stating i(t)=0 when there is a nonzero field.

Writing I=Q/T is the 'simple' definition of current. A more generalized definition comes from amphere-maxwell:

∫B.dl=µo∫(J+εodE/dT).dS. I'm sure you can solve this equation for current.

As for hanging 2x4's I see no connection, as your senaro is hypothetical, and not possible, while displacement curernt is real and measurable.

Can't wait for your next fable. You're gonna have to top all the ones before.

 

[MrAl]

Hello again,


The professor clearly stated that i(t)=0, not i(t)=Id, that means the current was zero. If the current was not zero, heck, we wouldnt have anything to talk about because the original Ampere's Law would apply and we would not need the updated version with the 'displacement' current. The added term with the time rate of change of electric flux was added later because i was equal to zero yet there was still a B field. You have to think about why we would need a new term if the current was already there.

We arent limited by his lectures either, there are plenty of other sites that specify that it is not a real current, and even some that specify that the whole concept of 'displacement' current is not needed anymore as the field describes the behavior good enough. The phrase "virtual current" comes up.

The experiment i proposed with the 2x4's is definitely possible. I just didnt specify how the shadow exits with the virtual string and im not sure i want to tell because the whole point is that we dont have some information and we are to figure out what is happening and we cant so we invent something. So if you want to say it's not possible guess again. So it's not a fable, but something that can easily be demonstrated but only if the true cause of the shadow was revealed.

To say that the current flows through a capacitor is too misleading, no matter how you look at this.

That equation is an equation for the magnetic field, how the magnetic field is defined, where it comes from, what causes it. The current density is clearly in one term and the rate of change of electric flux is in the other part. Why dont we just have another current like I2 in there instead dE/dt, because it's not a current.

You dont seem to realize that you are arguing another contradiction. You are saying that the displacement current is not a Q/t current, but then when you calculate the B field in the wire when i(t)=0 you say that there is a current flowing i(t)=id so that implies that id is a real current, yet you can not argue anymore that inside the capacitor there is a real current Q/t, so which is it?
Inside wires the current is Q/t. You're trying to say that i(t)=0 AND i(t)=id both at the same time. You dont seem to understand that, but lets look at this from another angle here.

We have i(t)=0 at SOME point in time, so say we solve i(t)=0 for t. That gives us t1, a real point in time. We solve for that time so we can say that i(t1)=0.
Now at the time the current goes through zero (t1) we know we have 0 amps because we specified that, but yet we still have a B field. We have 0 amps, not Id amps.
But if we had 0 amps and Id amps was not real, that would work out just fine. We would measure 0 amps, calculate B=0, hypothesize Id, calculate B=f(Id) and we'd be done.

You got me curious here now too How exactly are you measuring the displacement current in the wire?

 

[BrownOut]

The professor also said that displacement current flows through the capacitor. He also writes Id=I for the capacitor. Odd you want to quote him repeatedly, but still don't want to deal with all his statements. Cherrypicking.

You are trying to say i(t)=0 and i(t)=id; I never did. I said i(t)=0 is incorrect if the magnetic field is not 0. The amphere-maxwell equation is a gereralized equation that gives for current, an electron flow current and a displacement current. In other words, i(t) is the right-hand side of the equation, and is made up of two terms. The equation you keep writing for current just ignores one of the terms, which is OK, but the full equation is a more general description for current. And there are pleanty of websites that discuss id, but don't say anything about it not being a valad current, actually more than do. So, more websites confirm id than those that dismiss it ( not that I ever do science by counting websites; I leave that up to you and Ratchit ). Nobody has yet to tell me how you can measure a non-quantity.

So, once again, if you have non-zero B field, then you have non-zero current, no matter what the charge flow is. Thus, no matter how many times you write i(t)=0 when the field is non-zero, you're making a bad assumption, because the current cannot be zero, per amphere-maxwell.

I measure displacement current as I've described at least 1/2 dozen time before; by examing the B field. The displacement current can be observed, it can be measured and it can be quantified. Anything that prevasive has to be real.

I know your very proud of your string analogy, but I just don't see any merit. It's quite impossible for a non-entity to make a shadow, so there is no parallel to an entity that produces a very real magnetic field.

I comes down to if I believe you or Maxwell. Think I'll go with Maxwell on this one.

 

[Mr RB]

What happens inside the capacitor (either theoretical or actual) is completely irrelevant in electronics.

In electronics it is clearly understood that if there is a 2 pin device with 1 amp flowing into pin1 and 1 amp flowing out of pin2 the device has a current of 1 amp flowing THROUGH it and there can be no exceptions, with any 2 pin device this must be considered as true.

In a circuit diagram or circuit simulator program the 1 amp flowing THROUGH the component will be clearly understood and used the same in all calculations no matter what that part is.

In a practical sense the 1 amp flowing THROUGH the cap will blow an inline fuse just the same as if it was 1 amp THROUGH a different component.

In a capacitive reactance power supply the AC current flowing THROUGH the cap is the only source of power for the product.

The concept of current THROUGH a capacitor (or ANY 2pin component) is absolutely vital and fundamental to all aspects of electronics including design, testing, theory of the circuit etc.

To say that "the electrons don't actually go through, they just build up on plates" or similar argument is almost completely irrelevant to electronics and however true it may be it must take a *very* second place to the required understanding of current going "THROUGH" something.

 

[BrownOut]

Hi Mr RB, I always enjoy reading your opinions. I think it's remarkable that when one calculates id using amphere-maxwell, the result is always id=ic, where ic is the more often discussed conduction current. That bodes well with your comments about current through the capacitor, or any two terminal device. Though highly theoretical, I find the results interesting, because a mathematic abstraction actually produces results consistant with common understanding of how things work.

 

[MrAl]

Mr RB:
Yes but that declaration is on a different level of theory. we are now discussing the physics behind the current not the external circuital observations. Circuit theory ignores the physics in favor of simplicity. It's another viewpoint which is very valuable indeed, but overlooks the true physical nature of the capacitor. It's the same with the inductor. We often overlook the inductors magnetic field so that we dont have to include that in the analysis and that simplifies things. If however that assumption becomes invalid (as in the case of the non linear inductor) then we have to resort to a lower level of physics. I discussed this with Ratchit in detail in this very thread. Perhaps we need a new thread though for this new discussion?


Brownout:

See again you are saying that "I" said i(t)=0 and i(t)=Id, then you say that that is incorrect, then you say that i(t)=0 is 'incorrect' if the mag field is not zero. What the heck?

Which lecture does he say "the displacement current flows through the cap", i'll watch that one. If he does in fact say that, you do realize he could be speaking hypothetically dont you?

"It's quite impossible to make a shadow from a non entity"
It's quite impossible for *you* to make a shadow in that experiment. It's not impossible for me. Just because you cant understand the experiment that doesnt nullify it. It only nullifies it for you.

"(If it) comes down to if I believe you or Maxwell. Think I'll go with Maxwell on this one."
A statement like that does not help the discussion. I already know that you assume you are correct on this as you made it quite clear. Anyone arguing assumes that they are correct. Therefore either side can make the same (assumed) statement.

The real heart of your argument though is in this quote:
START QUOTE
You are trying to say i(t)=0 and i(t)=id; I never did. I said i(t)=0 is incorrect if the magnetic field is not 0. The amphere-maxwell equation is a gereralized equation that gives for current, an electron flow current and a displacement current. In other words, i(t) is the right-hand side of the equation, and is made up of two terms. The equation you keep writing for current just ignores one of the terms, which is OK, but the full equation is a more general description for current. And there are pleanty of websites that discuss id, but don't say anything about it not being a valad current, actually more than do. So, more websites confirm id than those that dismiss it ( not that I ever do science by counting websites; I leave that up to you and Ratchit ). Nobody has yet to tell me how you can measure a non-quantity.
END QUOTE

You said i(t)=0 if the mag field is not zero, yet when we use i(t) alone we get B=0. It appears that you are trying to say that i(t)=u0*i+u0*e0*dE/dt. But you see that is not how we are defining i(t). We are defining i(t) as the REAL current produced by a changing voltage v(t) that drives the circuit and it is a resistive load. Clearly when v(t) goes through zero i(t) goes through zero. That's how we know that we have something to talk about. If you want to say that the displacement current is real then you have to show how the current measurement is zero.

Your measuring the displacement current (as you've described 1/2 dozen times before) by examining the B field, but that's a self-fulfilling prophecy that does not prove that the displacement current is a real current. Whatever you use has to be able to convert a field into a real current, and so that constitutes an energy conversion which would invalidate the measurement.
That's similar to when i inserted the short wire inbetween the capacitor plates in an attempt to measure the 'displacement' current. A current in the wire shows up for sure, but as soon as the wire is removed the real current goes away. We say that, and get this now, "The displacement current is exactly equal to the conduction current".
So the statement you said above:
"Nobody has yet to tell me how you can measure a non-quantity"
is really just bunk. Because just like the short wire measurement, you did not measure the displacement current you measured the B field, used Maxwell-Ampere, then claim that the displacement current is real. It's the E flux change that causes the B field and so the B field is said to cause a hypothetical "displacement current", but still the E flux change came before anything else.

Ask yourself this question: Although the displacement current is in units of Amperes, if it is real, then why did i have to measure the field to get the displacement current? Why couldnt i use the ammeter? An ammeter measures amps so why doesnt it show up?

A capacitor made from two plates and a vacuum can not have any real current flowing though it. It's just impossible.

 

[Ratchit]

Mr RB,

The concept of current THROUGH a capacitor (or ANY 2pin component) is absolutely vital and fundamental to all aspects of electronics including design, testing, theory of the circuit etc.

To say that "the electrons don't actually go through, they just build up on plates" or similar argument is almost completely irrelevant to electronics and however true it may be it must take a *very* second place to the required understanding of current going "THROUGH" something

So the current is through the capacitor as it is for a resistor? You can keep a DC in a resistor for any length of time, but not in a capacitor, can you? If you tried to keep a steady DC, then either you would top out on your voltage source, or punch through the cap dielectric. If the current in a capacitor circuit passed through it, then the charge would not accumulate/deplete on the plates, would it? The charge accumulation/depletion is what gives the capacitor its exponential characteristics for transient voltage and reactance for AC voltage. That does not happen in resistors. I would say that the realization that caps accumulate charge, and do not leak significantly, is of primary importance in explaining what they do. How do you keep the current pass through "conception" apart from reality?

Ratch

 

[BrownOut]

Which lecture does he say "the displacement current flows through the cap", i'll watch that one. If he does in fact say that, you do realize he could be speaking hypothetically dont you?

Lecture 2. He would have no reason to speak hypothetically, as he just proved id=ic. The confusion part is he uses "regualr curret" and "current" interchangably. But look at this: https://www.youtube.com/watch?v=L0hcSXazjvc&feature=related It's a short lecture on the capacitor example, but this time the lecturer is more careful about what is conduction current, what is displacement curren and what is current. She clearly says displacement current is flowing through the capacitor, and without the ambiguous language. It's interesting that id satisfies the continuity condition in the charge conservation case, and the current conservation condition in the air dielectirc case. So, it's observable, quantifiable, measurable, and fits within the elecro-magnetic regime and is required by the law of conservation. I'd say it's a bullet proof case.

A statement like that does not help the discussion. I already know that you assume you are correct on this as you made it quite clear. Anyone arguing assumes that they are correct. Therefore either side can make the same (assumed) statement.

I'm not making any assumptions. Maxwell defined current per his addition to Amphere. You define it differently. I've chosen Maxwell's definition over yours. I've seen nothing to change my mind about that.

It's quite impossible for *you* to make a shadow in that experiment. It's not impossible for me. Just because you cant understand the experiment that doesnt nullify it. It only nullifies it for you.

It doesn't nullify me. A non-entity doesn't make a shadow. You statement is quite impossible and absurd.

But you see that is not how we are defining i(t). We are defining i(t) as the REAL current produced by a changing voltage v(t) that drives the circuit and it is a resistive load.

That's how you define it. Mr. Maxwell has a different definition.

Your measuring the displacement current (as you've described 1/2 dozen times before) by examining the B field, but that's a self-fulfilling prophecy that does not prove that the displacement current is a real current. Whatever you use has to be able to convert a field into a real current, and so that constitutes an energy conversion which would invalidate the measurement.

It's already a real current, so no conversion to a "real" current is necessary. There are ways to measure a B field that doesn't depend on induction, but I mentioned the easiest way to measure it. An easy way to measure a voltage is to convert it a magnetic field to deflect a meter pointer, but that doesn't invalidate the measurement of the quantity, thus just converting from one quantity to another doesn't invalidate the measurement, and as I said, a conversaion isn't necessary anyway.

you did not measure the displacement current you measured the B field, used Maxwell-Ampere, then claim that the displacement current is real

This is really a better way to measure current by directly measuring the field that defines the current, than how you would measure conduction current, but first converting it to a B field and using the B field to deflect a pointer. Either way, you're measuring the B field that defines the current. One could actually dispense with the conversion and use the B field directly. I'd say that's a better measurement. The B field defines the current, per Amphere-Maxwell, and so arised for real current.

Ask yourself this question: Although the displacement current is in units of Amperes, if it is real, then why did i have to measure the field to get the displacement current? Why couldnt i use the ammeter? An ammeter measures amps so why doesnt it show up?

Using the direct field ammeter measures the entire current. Using the field-conversion ammeter only measures one constituent of current.

 

[MrAl]

Hello again,

Ok, just to note, i am still enjoying the discussion as i think it brings out some interesting points about circuits and capacitor. I do want to restrict our discussion to vacuum capacitors because a dielectric material introduces other complexities which i really dont want to get into. Im sure you will agree that this is adequate, and later if you want to include dielectrics that's up to you. Thanks for your anticipated cooperation here.

It appears that we just dont agree on two or three points:
1. Either the 'displacement current' is real or it is not real.
2. Either the 'displacement current' can be measured by the field or not by the field.
3. Either people can invent experiments that you dont understand, or people are not allowed to invent experiments that you dont understand.

#3 is a simple experiment to show that we can hypothesize about things we dont fully understand. This is done every day, and Maxwell did this as well. You dont trust someone who invented an experiment just because you dont understand how it can be possible. The really strange thing about it is you didnt even bother to ask how it could be possible, you simple set off on your little assumptive adventure and never came back. If i invent an experiment and i say it's valid, then it's valid. If you say it's not then you're calling me a liar. I dont think that is fair at all.
The experiment is set up to show an analogy between the observed phenomena in the experiment and the observed phenomena in the circuit, but heck that is what scientists do every day.

#2 is the notion that you can have a current in amps and not be able to measure it with an ammeter. An ammeter measures amps, yet we can not measure the displacement current that way.

#1 You are saying that a real current can pass through a vacuum (capacitor). BTW you also say that you think you will agree with Maxwell on this one, so that proves right there that you are wrong about that, because Maxwell was wrong on that too. Thus you are already agreeing with someone who was already wrong.

So the way i see it is you are definitely wrong about a real current passing through a vacuum, and you believe that an experiment that you dont understand is immediately (and without any further inquiry) invalid. That's just a bit strange isnt it? You also have a current in amps that you can not measure with an ammeter, a device that measures amps. Doesnt that sound just a little bit strange too?

 

[BrownOut]

If i invent an experiment and i say it's valid, then it's valid. If you say it's not then you're calling me a liar. I dont think that is fair at all.

There is no reason to hurl accusations. I simply said non-entities cannot make shadows. If you can show an actual experiment, then you might have a point. So far, you have only speculated.

is the notion that you can have a current in amps and not be able to measure it with an ammeter. An ammeter measures amps, yet we can not measure the displacement current that way.

Sure we can. An ammeter that directly measures the field that defines the curent can measure both the displacement and conduction current = curent.

You are saying that a real current can pass through a vacuum (capacitor). BTW you also say that you think you will agree with Maxwell on this one, so that proves right there that you are wrong about that, because Maxwell was wrong on that too.

Maxwell was right. Current pases through vacuum all the time.

I understand your 'experiment', but I know it's not possible. I don't fall for everything I hear or read. If I did, I'd be getting free energy from all those free energy devices I've heard about.

 

[MrAl]

Hello again,


But an ammeter that "measures the field" is not measuring the current, it's measuring the field. Read your own writing: "(that) directly measures the field".

"Maxwell was right. Current passes through a vacuum all the time".
In a vacuum capacitor current does not pass through the vacuum.
Do you have any other example of a current passing through a vacuum?

Ok you didnt accept the experiment because you didnt like the fact that you didnt know all of the details but were asked to believe something that didnt seem plausible. Well then let me fill you in on the details then.
In the experiment, we showed that a 1 meter long string stretched out between two nails in a 2x4 cast a shadow on the 2x4 when lit from above. Then, we stated that with another set of nails in another 2x4 we also saw a shadow of the same length and width, even though there we did not use any string. We then hypothesized that there was a virtual string across the second set of nails and that simplified the (possible) calculation of the second shadow. We KNOW for sure that the second string doesnt exist, but we imagined that it did in order to simply the understanding of the second shadow. I also stated that this was an easy experiment to set up in real life. We might also note that the virtual string has dimensions equal to the first string, and of course the units of length and width are the same.
What i didnt tell was that there was another cord above the second 2x4, who's diameter and length was adjusted so that it cast a shadow that was exactly the same dimensions as the first shadow. I kept this hidden so that we would be forced to conceptualize the second situation without knowing all of the details.

BTW just because some people or groups are totally bogus about something (free energy) and you dont fall for it, that doesnt mean everything you dont understand falls within the same class of being bogus.