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Why conventional current?

  1. Oct 24, 2004 #1
    I have always taught that conventional current still is being taught and accepted is because that most laws in physics follow the notion of conventional current, such as fleming's left/right hand rule and all. But when I learnt about electrolysis in chemistry, where we are indeed concerned about the electrons themselves, it seems that conventional current is also used, why is this the case, when current do not really flow as conventional current states?
     
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  3. Oct 24, 2004 #2

    James R

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    It's convention!

    It is possible to have positive charge carriers or negative charge carriers making up a current. The conventional current flows in the direction that positive charge carriers would move, and in the opposite direction that negative carriers would move.

    If you don't want to specify what is carrying the charge, you can still talk about currents by referring to the conventional current.
     
  4. Oct 24, 2004 #3
    ^ hmm, but the only positive charge carriers in this case would be electrolytes, positive ions. Things like a battery and all set up a current made up of moving electrons, which are basically negative charge carriers only. And in electrolysis, we are concerned about where the electrons actually go, and can't possibly stick to the notion that current is actually flowing the opposite direction, right?
     
  5. Oct 25, 2004 #4

    ehild

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    Current means transfer of something in unit time. Water current means water flow from one place to other. If water flows out form a tap into a bucket the amount of water in the bucket increases with time.

    The same with the charge. The charge should increase at that place to where the current flows that means that the current must be the flow of positive charges.
    Of course, the charge would increase by the same amount if equivalent negative charges flow AWAY. But we consider the current positive if it increases the charge at the place to where it flows.

    It would be more logical to take the charge of electron positive. Than the direction of current would be the same as the direction of electron flow. Why not then? Because of the tradition.
    ******
    "Charge was discovered by the Ancient Greeks who found that rubbing fur on various substances, such as amber, would build up an electric charge imbalance. The Greeks noted that the charged amber buttons could attract light objects such as hair. ... The word electricity derives from ηλεκτρον, the Greek word for amber.

    By the 18th century, the study of electricity had become popular. One of the foremost experts was a man named Benjamin Franklin. Franklin imagined electricity as being a type of invisible fluid present in all matter. He posited that rubbing insulating surfaces together caused this fluid to change location, and that a flow of this fluid constitutes an electric current. He also posited that when matter contained too little of the fluid it was "negatively" charged, and when it had an excess it was "positively" charged. Arbitrarily (or for a reason that was not recorded) he identified the term "positive" with the type of charge acquired by a glass rod rubbed with silk, and "negative" with that acquired by an amber rod rubbed with fur. " <http://www.brainyencyclopedia.com/encyclopedia/e/el/electric_charge.html>


    ehild
     
  6. Oct 25, 2004 #5

    BobG

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    The difference is a little more than tradition.

    Moving electrons carry a charge from one place to another, but the movement of the electrons doesn't really explain the effect, very well.

    Imagine this:

    Nine students are sitting in desks 1-9 in a row with 10 desks.

    Ninth student moves back one desk, the empty desk has changed from desk 10 to desk 9.

    Eighth student moves back one, empty desk has changed from 9 to 8. And so on.

    After each of the students have moved back one desk, the 'hole' has moved up 9 desks (10 to 1).

    The empty desk is the effect of electricity and it moves at the speed of light. Each student is an 'electron' and they have moved substantially slower.

    For electrolysis, you would be more concerned with the actual movement of electrons than the movement of the electrical force.
     
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