Capacitors

[Jeanguypataterubberboot]

Thanks Gryd3. You explain very well.

Pierre

 

[Jeanguypataterubberboot]

@Jeanguypataterubberboot Nice setup by the way!! And you said you were new in electronics If you look up reactance it may help you understand AC in a capacitor, very interesting stuff.

Thanks, I started learning more about electronics when I got a ham radio license last year. I just wish I would have been more interested in it when I was in school and my brain was young and able to learn a lot quicker. I'm fascinated by it though and I'm looking forward to knowing a lot more.

 

[Ratch]

Gryd3,

"Slow down, and open your mind enough to try to understand others and how they are using their words"

Speed is irrelevant. Precision of expression is important when explaining something.

" I took a look at your post 27, and skimmed the replies and your getting into the same debate on other forums."

Nothing wrong with that, as long as I am correct in what I am saying.

"Our languages are not perfect, and neither is our use of words. Keep that in mind when you read someone's reply."

Much of the time it is grossly incorrect.

"... but it is common to have it called 'charged'. Don't argue the word being used, argue the mechanics of the capacitor. Your nit-picking things that don't need to be."

Common and wrong. The mechanics of the capacitor are that it is not being charged. That is a fundamental flaw in recognition of what is happening.

"To address the charges accumulating on one side and depleting on the other... step back and take a look at the bigger picture."

Don't you think I have done so many times?

"Yes, that is the end result, but the path of the 'charges' or electrons tell an external observer that the charge passes through the capacitor to a varying limited degree. Current goes in and current goes out. The exact mechanism here is that a different electron comes out, but the assembly appears to pass a current even though the individual components in the assembly do not. I agreed with you saying that 'electrons' don't actually pass through but energy, does. Now the mechanic here is the electrons' charge repelling other electrons, or the E-Field or whatever your region/school/teacher calls it. The mechanic is still the same. Electron gets forced onto one plate, which then repels an electron off the other plate which will then continue down the same path as if an electron had actually passed through. The surface area of course will dictate the rate at which this can actually happen, and the total amount of 'charge' or electrons that can pass."

No, the electrons only appear to pass through the capacitor. It is deceiving. As I explained before, the electrons get stopped at one plate and accumulate. The electrons at the other plate start to flow and deplete. This is caused by the voltage applied to the terminals, not by the repulsion of the electrons. I explained that before, too. This movement of electrons or current can only be sustained for a limited time.

"I will repeat my last statement, and say that both are indeed correct given your current reference."

No, only one explanation is correct with respect to electrons moving through a capacitor branch of a circuit.

"And we all know, a capacitor is made of two conductors."

Incomplete description. A capacitor contains two conductors, along with precise positioning and usually a dielectric. Anything else if just stray capacitance.

"... but if you pick it apart and look at the individual pieces as you have been doing, each conductor is 'charged' with an opposite electric charge."

Yes, that is what I have been saying all this time, and concluding that the total charge in a capacitor or battery does not change.

"We may not agree to the exact english word that must be used to describe each item, as there are numerous words in the English language that mean almost the exact same thing."

I think it is a case of using the wrong word to describe something that is not happening a certain way, and thinking that it is happening that way.

Ratch

 

[Ratch]

Thanks guys. Very informative discussion. I understand capacitors a lot better now. I am still a little confused though on the part that frequency plays in the capacitor. As the frequency goes up or down.

Pierre

As the capacitor accumulates and depletes charge on its plates, it forms a back-voltage that opposes the applied voltage to the capacitor. At lower frequencies, there is more time for the charges to accumulate and deplete so that a higher back-voltage can form. This results in less alternating current in the circuit containing the capacitor. When the frequency is high, the time for the back-voltage to accumulate is less so more alternating current can exist in the capacitor circuit.

Ratch

 

[Ratch]

Exactly. You assume that the 'conduction path' must be resistive, and since there is no resistive conduction path through a capacitor you maintain that there can be no conduction path through a capacitor. However, there is a conduction path through a capacitor that is capacitive in nature.

I still don't know what you mean by a capacitive conductive path.

Ratch

 

[Gryd3]

Ratch, Re-read my post and your response. This is why I'm telling you to slow down.
Don't argue for the sake of argument. You've dismissed all of everyone's points if they are not word-for-word the same as your text.
As stated, English is a complex language and not everyone is going to take the time to pick the best words... Heck, you don't even take the time to read and consider other's posts. Seriously. Re-read this lovely section that you yourself quoted. Give yourself 5-minutes and think about it. Let is sink in, consider it, then think about how you can pick it apart and write your reply.

"Yes, that is the end result, but the path of the 'charges' or electrons tell an external observer that the charge passes through the capacitor to a varying limited degree. Current goes in and current goes out. The exact mechanism here is that a different electron comes out, but the assembly appears to pass a current even though the individual components in the assembly do not. I agreed with you saying that 'electrons' don't actually pass through but energy, does. Now the mechanic here is the electrons' charge repelling other electrons, or the E-Field or whatever your region/school/teacher calls it. The mechanic is still the same. Electron gets forced onto one plate, which then repels an electron off the other plate which will then continue down the same path as if an electron had actually passed through. The surface area of course will dictate the rate at which this can actually happen, and the total amount of 'charge' or electrons that can pass."

No, the electrons only appear to pass through the capacitor. It is deceiving. As I explained before, the electrons get stopped at one plate and accumulate. The electrons at the other plate start to flow and deplete. This is caused by the voltage applied to the terminals, not by the repulsion of the electrons. I explained that before, too. This movement of electrons or current can only be sustained for a limited time.

As I stated in the text you quoted, the electrons don't actually pass through, but they appear to. You dis-agree with me, then summarize a portion of my statement anyway. I have highlighted some key words I hope you notice when you re-read it.

Seriously. 5-minutes.
Chill your shorts. I understand what you're posting and am not attacking you if it feels this way. You'll notice that I have not attempted disprove you. I have merely been expressing the same ideas with different frames of reference... ie looking at the capacitor as a whole, verses looking at it's components that make it up. I have also explained based on common words and descriptions I have learned from books, peers, and teachers. As unfortunate as it is, English language evolves and is not black& white. If the majority of people call it charged, then that is it's new definition and you need to learn to interpret how other people use their words. We are human, not machine, you need to learn to be more open minded and consider other opinions before opening your mouth.

Again. 5 Minutes.

 

[Laplace]

I still don't know what you mean by a capacitive conductive path.

When you see a current flowing into one side of a capacitor and a current flowing out of the other side, the capacitive conductive path is the part of the capacitor that allows that to happen. It should be self-evident.

 

[davenn]

When you see a current flowing into one side of a capacitor and a current flowing out of the other side, the capacitive conductive path is the part of the capacitor that allows that to happen. It should be self-evident.

no, I have to disagree with that. I have never heard of or can find any reference to "capacitive conductive path" in relation to capacitors, only in relation to capacitive sensors which is a whole different ballgame

if you have a reference to a scientific describing that process in direct relationship to a capacitor, I will be happy to read it
There is NO flow of current between the capacitor plates via the dielectric, unless the capacitor is leaky

Dave

 

[davenn]

"Slow down, and open your mind enough to try to understand others and how they are using their words"

Speed is irrelevant. Precision of expression is important when explaining something.

Gryd3,
precision is important, time and time again, particularly in the physics forum that I'm part of, I see where question posers are getting into problems of understanding and many times its is purely related to using incorrect terminology

"We may not agree to the exact english word that must be used to describe each item, as there are numerous words in the English language that mean almost the exact same thing."

in science, "almost the exact same thing " isn't really good enough. There are well established terminology terms for describing everything in whatever field of science --- biology, physics, geology ... whatever
When people stray from those terms, that's when confusion and misunderstandings set in and discussions like this thread get off the original topic

I have no problems with RATCH's posts
and please note his signature ....

cheers
Dave

 

[Ratch]

Gryd3,

" Re-read my post and your response. This is why I'm telling you to slow down."

I did, twice. What does speed have to do with it?

"Don't argue for the sake of argument"

Who is doing that?

" You've dismissed all of everyone's points if they are not word-for-word the same as your text."

No, I analyzed and corrected them.

"Chill your shorts. I understand what you're posting and am not attacking you if it feels this way."

I know you are not attacking me. A disagreement is not an attack.

"As stated, English is a complex language and not everyone is going to take the time to pick the best words..."

Language complexity is irrelevant. Many folks are using words to convey concepts that are completely wrong.

"As I stated in the text you quoted, the electrons don't actually pass through, but they appear to. You dis-agree with me, then summarize a portion of my statement anyway. I have highlighted some key words I hope you notice when you re-read it."

I disagree with your explanation of how electrons appear to pass through a capacitor. You said that the electrons on one plate repel the electrons on the other plate. Evidently you did not read my rebuttal of that theory in post #27. So I did not dismiss your declaration out of hand. It was already covered.

" I have merely been expressing the same ideas with different frames of reference... ie looking at the capacitor as a whole, verses looking at it's components that make it up"

I don't quite see it that way.

"...English language evolves and is not black& white."

Irrelevant. When used correctly, any language can be precise if the correct words are available and used.

" If the majority of people call it charged, then that is it's new definition and you need to learn to interpret how other people use their words. We are human, not machine, you need to learn to be more open minded and consider other opinions before opening your mouth."

A consensus of opinion does not make something right. Like for instance, NASA thinks their astronauts "walk" in space. Has anyone asked them what would happen if their tether breaks and they lose their grip on something? Would they walk away?

Ratch

[Mod edited for quote clarity ]

 

[Laplace]

There is NO flow of current between the capacitor plates via the dielectric...

And yet current flows through the capacitor. If current did not flow through the capacitor it would be a violation of Kirchoff's Current Law. Imagine a circuit which includes two nodes connected by a capacitor. The node equation for the summation of the current at a node contains a term for the current through the capacitor. It is easy to see that this is so by taking the Laplace transform of the circuit, where the current through the capacitor is expressed by the term (V1-V2)/(1/Cs). Looking at the operation of a capacitor in the complex frequency domain is just as valid as looking at it in the time domain, and conceptually easier. But the fact is that Kirchoff demands that current must flow through a capacitor. So if you accept Kirchoff's Law, then there must be a capacitive conduction path that exists.

 

[Gryd3]

And yet current flows through the capacitor. If current did not flow through the capacitor it would be a violation of Kirchoff's Current Law. Imagine a circuit which includes two nodes connected by a capacitor. The node equation for the summation of the current at a node contains a term for the current through the capacitor. It is easy to see that this is so by taking the Laplace transform of the circuit, where the current through the capacitor is expressed by the term (V1-V2)/(1/Cs). Looking at the operation of a capacitor in the complex frequency domain is just as valid as looking at it in the time domain, and conceptually easier. But the fact is that Kirchoff demands that current must flow through a capacitor. So if you accept Kirchoff's Law, then there must be a capacitive conduction path that exists.

The current flow as described by a flow of electrons does not actually flow through it due to the dielectric. There is an inbound and outbound current flow, but the actual path of the electron does not continue through the capacitor.
If you want to pass a note to someone behind a pane of glass, you can stick the note to the glass, then they see it and re-write it and continue to pass it around. The message continues on a different physical note because your paper cannot pass through the barrier.
If no one knows the layout of the building, it appears as though the note that goes in also comes out... The path is not 'through', because of the barrier. But the interaction at the barrier allows the path to appear to behave this way, even though internally it does not.

 

[Ratch]

The current flow as described by a flow of electrons does not actually flow through it due to the dielectric. There is an inbound and outbound current flow, but the actual path of the electron does not continue through the capacitor.
If you want to pass a note to someone behind a pane of glass, you can stick the note to the glass, then they see it and re-write it and continue to pass it around. The message continues on a different physical note because your paper cannot pass through the barrier.
If no one knows the layout of the building, it appears as though the note that goes in also comes out... The path is not 'through', because of the barrier. But the interaction at the barrier allows the path to appear to behave this way, even though internally it does not.

Nice analogy. I like it. Ratch

 

[davenn]

And yet current flows through the capacitor. If current did not flow through the capacitor it would be a violation of Kirchoff's Current Law. Imagine a circuit which includes two nodes connected by a capacitor. The node equation for the summation of the current at a node contains a term for the current through the capacitor. It is easy to see that this is so by taking the Laplace transform of the circuit, where the current through the capacitor is expressed by the term (V1-V2)/(1/Cs). Looking at the operation of a capacitor in the complex frequency domain is just as valid as looking at it in the time domain, and conceptually easier. But the fact is that Kirchoff demands that current must flow through a capacitor. So if you accept Kirchoff's Law, then there must be a capacitive conduction path that exists.

no it doesn't
you really really need to get this understanding
current flowing in and out of either plate DOES NOT constitute as a current flowing THROUGH the capacitor

 

[Gryd3]

Nice analogy. I like it. Ratch

Tried to make a similar analogy with magnets further up, as I felt it more closely resembled an electron, but I figure I didn't quite explain it correctly to get my point across.

 

[Laplace]

...it appears as though...

So are you making an appeal to illusion & magic? Or are you stating that device characteristics specify how a device operates at its terminals?

 

[Laplace]

...current flowing in and out of either plate DOES NOT constitute as a current flowing THROUGH...

With any two-terminal device where current flows into one terminal and out the other terminal, current is flowing through the device. There is no escaping that realization.

 

[Gryd3]

So are you making an appeal to illusion & magic? Or are you stating that device characteristics specify how a device operates at its terminals?

Magic!

Actually, the appearance of current 'through' the device is made by observing the external terminals without knowing the internal behavior of the device.
Using current definitions for 'current' as a charge, electron, or electron charge still result in the electron stopping on one plate unable to pass through the dielectric. It does however interact with the electrons on the other plate though.
I think it's this interaction that has been incorrectly called a capacitive current path. The behavior is capacitive, but current does not flow through...

How about I explain what's going on in my head with a picture?

The above image is an imaginary device, but can be built... It's simply a plunger in a canister attached to a spring.
As water flows into the device, an equal volume of water flows out the other end. As the spring compresses, the pressure required to continue flow climbs. As this continues, the device will fully saturate and the plunger will no longer move.
Looking at this device, can you say that there is a path for water to flow?

If I did not show you the picture and gave you this device, you would certainly say that this device does have a path for water flow by experimenting with it... unless you put purple water in one end, and observed normal water coming out the other you would assume the path is unobstructed, and slowly closes as more water flows through.
This device's plunger and seal is like that of a capacitor's dielectric. The exact mechanism that the electrons interact is different, but similar enough to warrant this device as being used to give a general idea.

Edit: A similar device exists already in hydraulic machinery... and although fluid gets pumped in and out two or more ports, the fluid does not actually pass through the device unless the internal seal is damaged or imperfect.

 

[Laplace]

Looking at this device, can you say that there is a path for water to flow?

It is obvious that fluid flows through the device, until it stops flowing. But unlike a capacitor, you have introduced a non-linearity. Nevertheless if the pressure keeps increasing in an attempt to cause more fluid to flow, the device will eventually fail -- just like a capacitor.

 

[davenn]

With any two-terminal device where current flows into one terminal and out the other terminal, current is flowing through the device. There is no escaping that realization.

Come on Laplace, you have been around long enough not to really believe what you are writing .... surely !! ??
NO it isn't and you have several times, by several people, been given the reason why this isn't so

Dave