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current flow?

Discussion in 'General Electronics Discussion' started by brinks, Jul 28, 2015.

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  1. brinks

    brinks

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    Dec 16, 2013
    hi,
    can some one explain to me what conventional current flow is and the difference between conventional and electron flow. how can they be opposite of each other?
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,271
    2,718
    Jan 21, 2010
    Conventional current flow was the result of a 50/50 guess that was made long ago.

    Electron flow is how things really work (and was clearly shown to be the way with the first vacuum tubes).

    The conventional flow is so ingrained into so many things that it is still used. Except for a few cases involving electron emission, or looking at the physics of how things work at the atomic level, it rarely makes a difference.
     
    Arouse1973 likes this.
  3. brinks

    brinks

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    Dec 16, 2013
    Thank You very much that was very helpful and cleared up my confusion
     
  4. duke37

    duke37

    5,276
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    Jan 9, 2011
    If you draw a circuit diagram with the positive line at the top and the negative at the bottom, then arrows pointing down (diodes, leds, transistors) will conduct and pass current either by electrons or holes.

    Arrows pointing upwards (Zener diodes or relay catch diodes or power supply diodes) will not conduct unless they are over driven.
     
  5. Minder

    Minder

    2,917
    613
    Apr 24, 2015
    The blame has been placed at the feet of Ben Franklin for the mix up!
    Also the reason the check valve symbol for the Diode is backwards (electron flow wise).
    M.
    .
     
  6. brinks

    brinks

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    Dec 16, 2013
    Thank You
     
  7. brinks

    brinks

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    0
    Dec 16, 2013
    Thank You
     
  8. Ratch

    Ratch

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    310
    Mar 10, 2013
    First of all, "current flow" is technical slang that really should not be used. One should say charge flow, or current existence, or current present. Literally, current flow means "charge flow flow", which is redundant and ridiculous.

    Conventional current flow should be called "mathematical current". That means that the polarity of the charge carriers are ignored and charge flow is assumed to go from the positive terminal of the voltage source, to the load, and then to the negative terminal. In other words, it assumes that current consists of positive charge carriers. This makes calculations easier, because you don't have to worry whether the charge carriers are negative electrons as in wires, or positive holes like in semiconductors, or cations and anions in electrolytes. You first perform your calculations using the mathematical convention, and then if necessary to know the true direction of the charge flow, keep the same direction for positive carriers and reverse direction for negative carriers. I have seen folks really get tied up in a knot when they start to worry about the polarity of the carriers before they start calculating.

    Some folks blame Ben Franklin for what they call a mix up. Nothing is further from the truth. There are as many positive charges in the universe as negative charges, so if he called electrons positive, other charge carriers would be labeled different from what we are now used to.

    As you have probably noticed, semiconductors and ammeters are all marked according to the mathematical convention.

    If you or anyone have any questions about this, please post.

    Ratch
     
  9. brinks

    brinks

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    0
    Dec 16, 2013
    thank you
     
  10. Minder

    Minder

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    Apr 24, 2015
     
  11. Ratch

    Ratch

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    310
    Mar 10, 2013
    I think the designation is arbitrary. Why should electrons be the arbiter of what is charged to what polarity? There are charge carriers that have the opposite polarity with respect to electrons, and they have the same status as electrons do. Read the link below. Notice the point it makes about a static charge being made without electrons. I define static charge as an accumulation of charge carriers without a conduction path to go anywhere.

    Ratch

    http://www.austincc.edu/wkibbe/truth.htm
     
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