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Current philisophy

Discussion in 'Electronic Basics' started by Rodney Kelp, Mar 31, 2005.

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  1. Rodney Kelp

    Rodney Kelp Guest

    So, are they still teaching hole flow in electronics schools or are they
    back to electron flow?
     
  2. John Larkin

    John Larkin Guest

    Current flows [1] from positive to negative. Engineering and physics
    schools never taught anything else. The military and some trade
    schools taught electron flow, and may still. That confuses the hell
    out of the poor students.

    "Hole flow" happens in semiconductors.

    John


    [1] the usual fatheads will get prissy about the phrase "current
    flows", of course.
     
  3. Active8

    Active8 Guest

    No. The terms are "pedants" and perhaps "pissy". And going back to
    basic physics, we always talked about electrons accelerating in a
    field and about charge per time. Since we were talking about the
    charge of electrons, I always got the impression that we were
    talking about negative to positive. The positive to negative
    convention was introduced in electroncs.
     
  4. They are still teaching positive charge flow (=current), and that is what
    we always talk about.

    Forget about electron flow unless you have some special reason to
    consider elementary particles movements or molecular chemistry in some
    special cases.
     
  5. John  Larkin

    John Larkin Guest

    Nicely self-referential!
    The positive to negative convention was introduced by Benjamin
    Franklin a long time before electronics was invented or electrons were
    discovered.

    John
     
  6. R.Spinks

    R.Spinks Guest

    Hole flow is still taught in semiconductor classes.
     
  7. Me

    Me Guest

    For me in beginning physics, we talked about electric fields as pointing
    from a positive charge to negative charge, so that a positive test
    charge will feel a force pushing it towards the negative charge. This
    morphs into positive charges flowing out the positive side of a battery,
    the right rule giving you the right direction for the magnetic field set
    up by that positive current, and so on. You could just as easily talk
    about negative charges flowing the other way, and using a left hand rule
    instead. That is if I say 6A is flowing from the right side of your
    screen to the left, then that is either 6 A worth of positive charge is
    flowing from right to left, 6 A worth of negative charge flows from left
    to right. As the Circuits book I just finished they actually go to
    great pains to establish that being consistent when working a problem is
    the only thing that matters.

    Hole flow is different, in that holes don't really flow in a
    semi-conductor, right. That is given a positive type semi-conductor
    there are holes in the atoms making up the material, and electrons hop
    in and out of the holes, the atoms being fixed in place, so the
    appearance is that holes are flowing the opposite way through the
    material. I never really had a formal electronics class (I always liked
    the AoE approach where you don't really care about the internals of the
    devices, but just how to make them useful), so maybe I'm wrong.

    Craig
     
  8. Active8

    Active8 Guest

    Moi? I just state it correctly. I don't think I get pissy about it,
    but I might point it out.
    Someone mentioned that here and/or in an article on lightning.

    Let me rephrase that. The positive to negative convention was
    introduced to *me* in electroncs ... *after* I learned that
    electrons flow from neg to pos which was years before I took
    physics.
     
  9. Active8

    Active8 Guest

    ^^ Hey, Me. You're Me ;)
    Yup. My pre-physics knowlege of electronics probably caused me to
    favor the opposite view - a negatice charge being attracted to the
    positive charge. But remember, you don't need a negative charge for
    a positive one to set up a field or exert a force on another
    positive charge.
    Yeah, but it doesn't hurt to talk pos to neg with others. That way
    we're always on the same sheet.
    Right. They don't *really* move. It's just an unoccupied electron
    position. Holw flow is discussed as is their drift velocity. If you
    want a bit of fun learning, check out "The Britney Spears Guide to
    Semiconductor Physics." If you want the same thing on a paper plate,
    try MIT's open courseware. 6.021 Microelectronic Devices and
    Circuits
    AoE serves its own purpose. The formal approach has it's own merits.
    Ok. Me is Craig. How's that for ebonics? :)
     
  10. PeteS

    PeteS Guest

    As numerous others noted, both are taught. Although there are comments
    about holes not really moving (each individual hole roughly stays put),
    the conduction in P material actually effectively takes place in the
    valence band, not the conduction band.

    That's the reason P-channel devices are slower, incidentally (lower
    energy level).

    All of this is part of quantum mechanics (and to quote Niels Bohr, as
    close as I can 'anyone not outraged on first hearing about quantum
    mechanics did not understand what has been said').

    Cheers
    PeteS
     
  11. John  Larkin

    John Larkin Guest

    Oh, of course. You're the only one who matters.

    John
     
  12. John  Larkin

    John Larkin Guest


    Except that Fluke won't sell you a negative-charge ammeter, and no
    engineer is going to keep you on the payroll for long if you keep
    getting the signs reversed.

    John
     
  13. Active8

    Active8 Guest

    Ok. It was introduced to me, perhaps you, and most likely others at
    some point in time after we started learning about electronics.
     
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