Current flow

Discussion in 'Homework Help' started by amilton542, Feb 27, 2011.

  1. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    The definition of current is the flow of electrons from negative to positive and the current flows from positive to negative. When a potential difference is applied the electrons will move to make the eletric field zero but because theres a potential difference they fail and they continue to move from negative to positive so my question is what is this current flowing from positive to negative, is it the electric field lines that the electrons ride along which in turn the angle they come of the field lines causes them to smash into the impurities causing resistance
     
    Last edited: Feb 27, 2011
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    That is contradictory. Electrons carry a negative charge, and move from a negative source to a positive potential. Current is the movement of charge, so current flows with the electrons.

    The place where there can be a current of positive charges is in a battery, where the chemistry acts to keep the terminals at differing potentials. The last part of the question - "is it the electric field lines that the electrons ride along which in turn the angle they come of the field lines causes them to smash into the impurities causing resistance" is hard to make sense of.

    Have you spent some time studying basic DC electricity?
     
  3. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    Ive been looking at eletrostatics and it says the negative electron will ride the electric field lines in opposite direction to which the field lines are travelling, or i may have it the wrong way round, it was making me wonder if it was down to the electric field. So what about when dealing with AC?
     
  4. Adjuster

    Well-Known Member

    Dec 26, 2010
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    The "conventional" current flow from positive to negative is just that: it is a convention which allows us to determine current flow direction from the direction of potential differences. As far as I know, this had become widely established before the electron concept was introduced, and so remained in place.

    I do not think that it is very helpful to imagine electrons riding field lines and then coming off them, as if they were beads attached to wires. Perhaps it would be better to say that the electrons undergo acceleration in the direction of the field, and also interact (collide) with particles along the way.

    Typically, most of the electron velocity in a solid conductor will be random, with a relatively small average drift superimposed when an electric current is passing. Electrons will therefore rarely be travelling exactly in the direction of the acceleration due to the field.
     
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  5. Georacer

    Moderator

    Nov 25, 2009
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    @beenthere

    Since the direction of the current is important here I 'll post the following:

    Current is collinear to the movement of charge in general, but its direction can be selected either by the conventional rule, or the electron direction flow, as our e-book describes very well. As a result, we can say that the current flows in the same direction as the negative charge, or in the same direction as the positive charge.

    @amilton542

    Please punctuate your text to make it more understandable. Is your question the definition of current?

    An electric field in the reason and the cause for the movement of the electrons. Since the current described as the move of charge, we can say that the current is the result of an imposed electric field.
     
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  6. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    I always thought electron velocity is constant because the potential difference is constant. ok thanks
     
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