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AC flowing through a cap. What actually happens?

Discussion in 'General Electronics Chat' started by qtommer, Feb 25, 2011.

  1. BrownOut

    BrownOut Banned

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    Great point. He has the right to butcher the language all he wants, then lectrues everyone else on 'proper' usage, even though his version isn't any more proper. Everone has to play by his rules, everyone except him that is.

    Also note that in his world, e fields exist in equipotentials.
     
    Last edited: Mar 1, 2011
  2. Ratchit

    Ratchit Well-Known Member

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    misterT,

    Conventional current exists in the direction opposite from the electron flow.

    Folks should just refer to it as simply charge flow and add descriptives from there. Back/forward charge flow, less/more charge flow, charge flow through a resistor, etc. Also, back/forward current, more/less current, current through a resistor, etc. But don't use both current and flow together.

    Not always, but sometimes yes. Words are amenable to their meaning being supplemented by adjectives and adverbs, even if it doesn't make sense. Remember "space walk"?

    No, I have had a good academic education.

    I know. Otherwise you would have said "Conventional current flows in the opposite direction from the electrons".

    "Current flow" contains a redundancy while "voltage travel" does not. I should have said "establish itself" instead of travel.

    Ratch
     
  3. Ratchit

    Ratchit Well-Known Member

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    BrownOut,

    What an exaggeration! Using a colloquial expression is not "butchering" the English language. Objecting to a word or phrase being used, and explaining why is perfectly proper. I don't have any rules anyone has to play by. You should pay more attention to your typos.

    I challenge you to show where I did not know the difference between a scalar field and a vector.

    Ratch
     
    Last edited: Mar 1, 2011
  4. dave

    Dave New Member

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  5. BrownOut

    BrownOut Banned

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    I didn't say anything about exaggeration. Your descriptions are wrong, colloquial BS aside, which has no place in a technical discussion. It's utterly hypocritical to use incorrect language, no matter how you excuse it, while thinking you need to correct the language of others. And I haven't pointed out your typos because I haven't wanted yet another path to lose focus. Leave it to you to find another way to derail any topic.
     
    Last edited: Mar 1, 2011
  6. BrownOut

    BrownOut Banned

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    Looks like you can be more careful with your typos too. Or else cease obsessing over every else's minor errors, while you make exactly the same mistakes.

    Why should I accept that challege, when I never make any such claim?
     
    Last edited: Mar 1, 2011
  7. ljcox

    ljcox Well-Known Member

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    I have just found and scanned this thread.

    I'm sure the OP will have been thoroughly confused by it.

    I presume that terms & concepts such as current, current flow, charge and discharge, etc. were coined in the 19th century by people such as Gauss, Faraday, Maxwell, etc. These terms & concepts have been accepted by thousands of us since.

    I daresay that they knew of the shortcomings of these terms and concepts.

    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.
     
  8. misterT

    misterT Well-Known Member Most Helpful Member

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    "Current flow" does not contain redundancy. It does not mean "charge flow flow". Maybe I need to repeat the point of my last post because you seemed to miss it:

     
  9. BrownOut

    BrownOut Banned

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    Thanks Mr.T. I agree completely. There is no redundancy. Your understanding of current and language is on point.
     
    Last edited: Mar 1, 2011
  10. Ratchit

    Ratchit Well-Known Member

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    misterT,

    Current already means the smooth continuity (direction and path) of the charge. It doesn't have to be repeated.

    Ratch
     
  11. Ratchit

    Ratchit Well-Known Member

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    ljcox,

    You don't. A current exists just fine from the gun to the screen of a CRT containing a vacuum.

    Ratch
     
    Last edited: Mar 1, 2011
  12. BrownOut

    BrownOut Banned

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    That's false. Current is only a measure of an amount of charge passing a point per unit length of time. Current does not imply smooth continuity. Charge movement is anything but smooth.

    Further, current doesn't say anything about direction or path. That's why direction must be specified along with the current. And current is defined at a single point, so no path is implied.
     
    Last edited: Mar 1, 2011
  13. misterT

    misterT Well-Known Member Most Helpful Member

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    So you think that "current path" is also redundant?
     
  14. ljcox

    ljcox Well-Known Member

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    True, but that is a flow of charge carriers.

    There is no flow of charge carriers with Displacment current.
     
  15. Ratchit

    Ratchit Well-Known Member

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    misterT,

    No, I agree current has a path and direction. Whatever it is can be specified. For instance, "current through this coil", "reverse current", etc. However, "current flowing" is redundant because current is already defining a flowing charge.

    Ratch
     
  16. Ratchit

    Ratchit Well-Known Member

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    ljcox,

    True. Ideal dielectrics do not contain free charges, but they do contain bound charges. An external electric field can induce electric dipoles with the bound charges of the material which in turn will modify the electric field both inside and outside of the dielectric material. I am not going to try to explain how that happens. I refer you to a good book on electromagnetics and this link. Displacement current - Wikipedia, the free encyclopedia

    Ratch
     
  17. BrownOut

    BrownOut Banned

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    Wrong again. Current is a scaler quantity, and as such, has no path or direction. You just proved what you challenged me to prove earlier.
     
    Last edited: Mar 1, 2011
  18. ljcox

    ljcox Well-Known Member

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    Where are the bound charges in a vacuum?

    According to the Wikipedia link the displacemnt current is due to the changing electric field.
     
  19. Ratchit

    Ratchit Well-Known Member

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    ljcox,

    There aren't any. A perfect vacuum is "free space".

    Which is caused by the polarization of the dielectric molecules. Did you follow the second link from the previous link to http://en.wikipedia.org/wiki/Polarization_(electrostatics) ?

    Ratch
     
  20. BrownOut

    BrownOut Banned

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    Dispacement current exists in free space. No charge carrier is required for displacement current. No polarization of any dielectric molecule is required. Dispalcement current exists without charge carriers. You should try reading the links you provide.
     
    Last edited: Mar 2, 2011
  21. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello again,


    Ratch:
    You seemed to have missed post #79.
    The point there is that even after we qualify 'energize' with a success, we can not tell something important about the battery that we can when we use the word 'charge'.
    You really need to read that post again but i'll repeat part of it here:

    ----------------------------------------------------------------------------------------------------------------------------------------------------------------
    In the case of 'energize', did we successfully store energy in the battery or not? We cant tell even though we stated that the battery did in fact 'energize'.
    In the case of 'charge', we were able to tell that the battery successfully stored energy because once we qualify that with a 'success' there's only one way to take it.

    Both forms have been "acknowledged with a successful accomplishment" so your argument that they were not is void.

    So when we use the word 'energize' we actually say LESS than when we use the word 'charge'.
    ----------------------------------------------------------------------------------------------------------------------------------------------------------------
     

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