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Elementary question - what makes the current flow?

Discussion in 'Electrical Engineering' started by Who Am I?, Mar 7, 2010.

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  1. Who Am I?

    Who Am I? Guest

    There are many equations to describe what happens whenever
    it does happen, but why does the current flow in the first place?

    I used to think that it was electrostatic pressure caused by all
    the electrons being bunched up against each other and so
    pushing them apart, but someone said to me recently, that
    the electrons are merely being dragged along by the travelling
    electric wave.

    So, why does the current start flowing in the first place
    (when there is no wave to drag them along)?

    And why does it keep flowing?
     
  2. Bill

    Bill Guest

    I think the "ions" are migrating in one case...
    http://en.wikipedia.org/wiki/Galvanic_corrosion
     

  3. Current is the same at any point along the circuit, so the 'push' is
    the same everywhere. Where "work" is done, the push results in heat, but
    the push is the same, nonetheless. Where there is no work, as is the
    case with an ideal conductor, there is no heat, as it pushes right
    through easily, but the push is the same nonetheless.

    In a conductor the push is supposed to be "easy" on the conductor.
    That's why we use them. That is also why they have limits to how much
    one can push through them. Even they begin to heat at some point, which
    proves that they are not "an ideal conductor", but we have managed to get
    pretty damned close.

    So you are wrong., Bill. You may have had an idea for an analogy, but
    it fell on its face. Try again. The push is the same everywhere. The
    thing that differs is the work that gets done on all the little parts
    along the way. The load or work site is one part. Each piece of wire is
    another. Each item has their own little resistance to present to the
    power source. The whole 'circuit' is made up of these pieces.

    The push is the same, the "work" done along the way at each 'piece' is
    what differs.
     
  4. Rich.

    Rich. Guest

    Electricity is the transfer of electrons from one atom to the next,
    traveling in the same direction.
     
  5. Bill

    Bill Guest

    And then there is "hole flow"...
    http://everything2.com/title/hole+flow
     
  6. Guest

  7. A pretty big one flowed between your ears.
     
  8. Guest

    Guest Guest

    -----------------------------------
    Rather than consider electrons going one way filling holes which ,as a
    result, are going the other way, there is an approach, when considering the
    overall effect rather than the particle/non-particle motion (ignoring
    waves) use the classical current definition as in the direction of "positive
    charge" flow and stick with a single convention and eliminates a lot of
    guessing- "do I stick a negative sign in here or not?"- particularly
    problematic with AC.
     

  9. Which, of course, makes it easier to relate to any work product involved.
     
  10. Who Am I?

    Who Am I? Guest

    Thanks, your vote lies with the electrostatic pressure explanation; the
    greater the packing density of electrons, the greater the electric field.
     
  11. Rich.

    Rich. Guest

  12. "Packing density"? Who are you? You're an idiot, that's who.
     

  13. Doo doo, doo doo...

    Doo doo, doo doo... (Twilight Zone inflection)
     
  14. Who Am I?

    Who Am I? Guest

    .... < Palpable bollocks deleted > ...

    You are quite wrong in your assumed assessment of me.

    I completed an electronics degree over 20 years ago, and looking at
    the shelf of textbooks I mused that if I didn't get around to reading them
    again soon, I never would.

    So, out of interest, I started reading them all again, and came to the
    conclusion
    that there was a great deal left unsaid and unexplained, even at the degree
    level.

    I also accept that despite my level of education, that I do not know
    everything,
    and in pursuit of the truth, am prepared to admit my limitations in order
    to achieve intellectual satisfaction.

    I perceive now, that at whatever level one studies electricity, from the age
    of
    11 years upwards, that one is presented with a series of paradigms, none
    of which are complete, and all of which are misleading to some extent.

    Even at the level of Maxwell's Equations, electric charge is presented as
    point
    function akin to mass, whereas the physicist might claim that the electron
    is
    not a point, but a wave function.

    So, as a part of my extended revision, I awakened the paradigm of electrons
    being bunched together against their mutual repulsive forces (the "packing
    density" sneered at in another post by a further example of rampant
    childhood)
    and the electric current (and I am definitely discussing electrons and not
    positive
    ions) being caused by that pressure from the electric field.

    However, in discussion with a fellow radio ham (for such am I also) he
    suggested
    that the current flow in a waveguide is not caused by the mutually repulsive
    electric field between electrons, but that the electrons are carried along
    under the
    influence of a travelling e-m field and that the original emf that set the
    wave in motion
    is no longer relevant.

    Hence the question that I posed.

    Perhaps I was in error in posing a question about elementary matters in
    language
    that was itself more redolent of the elementary school and so attracted
    comments
    from one or two who should perhaps still be confined to the classrooms of
    that elementary school? If so, then I apologise, but I'm still interested in
    the
    elementary mechanisms of electric current, but from a perspective of one who
    has experience of much more in-depth paradigms.
     
  15. Reading? Novels are for reading. Textbooks meant for learning are for
    STUDYING, which it is obvious never happened.
     

  16. Bwuahahahahahahahahaha!
     
  17. Who Am I?

    Who Am I? Guest

    Yet another inhabitant from the elementary school seems to have escaped
     
  18. Who Am I?

    Who Am I? Guest

    I pity you because either you are annoyed that you don't know
    the answer, or else you are incapable of partaking in a public debate
    in a seemly fashion.

    <PLONK!>
     

  19. Yeah... YOU, ya dumbfucktard.
     
  20. The answer to what, you stupid ****? There was no valid question
    posed.

    There was no debate either, idiot!

    Unless you want to debate the fact that I say that you learned
    absolutely NOTHING when you took the electronics course.

    You're an even bigger retard than I originally estimated.
     
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