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I Nature of electric current

  1. Mar 16, 2016 #1
    what is electric current........a scaler or vector?? ........well I personally believe that it is somewhere in between the two extremes (what is not 0,need not be an 1 either :oldbiggrin: ) ...........particularly because of the strange similarity we see in vector addition and phasor addition)............some people call it a constrained vector.......let us discuss
     
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  3. Mar 16, 2016 #2
    electric current is defined as time rate of flow of charge -so naturally it has a direction and a magnitude .
    some phenomena depend on the direction of current - in electrical circuits the flow is restricted so the vectror takes a circulatory turn /some people may be calling it constrained to move in a particular way- charges can move due to field effect and the current element has a definite direction
     
  4. Mar 16, 2016 #3

    Drakkith

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  5. Mar 16, 2016 #4
    you are very much correct.
    well i was referring to the direction of current in terms of motion of charges - may not be in electrical circuits .
    for example if we take the effect on current element in a magnetic field or the circulatory charges leading to current - there we take the current in a definite spatial direction- /calculation of force on a current carrying conductor.
    in those cases we take the vector product of current element with magnetic field vector..
     
  6. Mar 16, 2016 #5

    Merlin3189

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    And when AC current is represented as a phasor?
    This is a vector in an abstract 2D space, but whether that counts ...?
    Perhaps we should not be saying, "Is current a vector?", rather, "Can current usefully be modelled by a vector?" After all, that's what a vector is, a mathematical abstraction. The world is not full of little arrows - they're just in our minds and on our diagrams.

    Edit: & just going back to OP, "What is electric current........a scaler or vector?" Is that a real question? Should it not be, "Can we (usefully) model electric current as a scalar or a vector, in some particular context."
    It is like my pet hate - is light a particle or a wave? No, light is light. Sometimes it is useful to use a wave model, sometimes a particle model, but light isn't a model. Even if people cleverer than me know a model that fits all known situations for light, then it is still a model that we can use to make predictions about what real light actually does.
     
    Last edited: Mar 16, 2016
  7. Mar 16, 2016 #6
    1st of all I am not saying that current is a vector, but I am arguing that it is not a scaler also..........phasors are added just like vectors....and the reference for them is intial phase=0.....now.......direction is always w.r.t the reference co-ordinate system you choose according to your convenience..........and your reference will give you the result which you want....nothing is absolute in this world.........as per as calculation is concerned in pen-paper, directions can come from chosen reference....... can't we think phase as a metaphor for direction while dealing with phasors? ....... in that sense,I opine that current falls somewhere in between scaler and vector.
     
  8. Mar 16, 2016 #7

    Dale

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    Do you have a reference which shares this opinion?
     
  9. Mar 16, 2016 #8

    cnh1995

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    As far as I know, current is a scalar. In KCL, we add currents algebrically at a node. In case of ac circuits, phasors are rms values.
    https://lh3.googleusercontent.com/proxy/cTRommP4ZE43NDXHNxeM5dJ1LBBJCPaUXfx-s63iEVycNbLpnAyHA94ZLF8tVo4p2NHANLkrQ6N05WU5xoRUDuLNAfDoaxPeie4lkj0nXc1t=w399-h241-nc
    Here, Is will be phasor addition of IR, IL and Ic and they're all rms values. But if we consider instantaneous values, they can be added algebraically. We can choose the sign of current depending on wheather it is entering or leaving the node, but we can add the currents algebraically. For magnetic circuits, direction of current determines the magnetic flux direction and magnetic polarity but that's all. I haven't seen components of current like components of vectors in different directions.
     
  10. Mar 16, 2016 #9
    I googled "is current scalar,vector or constrained vector".......and went on the first facebook link
     
  11. Mar 16, 2016 #10

    Vanadium 50

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    And you think this is a valid reference?
     
  12. Mar 16, 2016 #11

    jtbell

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    The current density at a point inside a conductor is a vector, ##\vec J##.

    The current in a wire is the surface integral of ##\vec J## over a cross section of the wire, which is a scalar, I: $$I = \int {\vec J \cdot d \vec a}$$
     
  13. Mar 16, 2016 #12

    Dale

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    Please review the forum rules regarding acceptable references on PF.

    The post by jtbell completely answers the question. Current density is a vector, current is a scalar.

    Since the question is answered and since there are no relevant references regarding anything "in between", this thread is closed.
     
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