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Direction of current flow?

  1. Dec 17, 2014 #1
    In the following diagrams:
    ll0jWm2.png

    and:

    0jaRP0l.png

    Is current flowing horizontal or vertical&horizontal?
    I'm sure for the rectangle one the flow of current is horizontal, but not sure of that square.
     
  2. jcsd
  3. Dec 17, 2014 #2

    dlgoff

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    This "analogy"(?) doesn't tell me anything about current. If anything, it might suggest a higher potential in the second one.
     
  4. Dec 17, 2014 #3

    donpacino

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    In both of the diagrams the current flow is both vertical and horizontal.
    Assuming the voltage source has a positive value, current will flow from the voltage source into the bottom right corner of the rectangle and then to the upper left corner of the rectangle, then back around to the source.

    That being said, asking if the current flow is vertical or horizontal is a very strange question.

    Why do you need to know this?
     
  5. Dec 17, 2014 #4
    Why? It's quite simple, a voltage source connected to different shapes of conductors.
    I wanted to know if they flow of current would be strictly horizontal on the first one, and both horizontal and vertical for the second.

    To be exact, can the direction of current be assumed like so:
    8euskdz.png
    And:

    6fDqPud.png

    Is it evenly divided, as to how some current flow vertical and some current flows horizontal(50/50)?

    Wanted to see how the "shape" or dimensions of a conductor, and where it's connected had an effect on direction of current.
     
  6. Dec 17, 2014 #5

    davenn

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    the current will flow throughout the conductor, not just in a narrow line across it
     
  7. Dec 17, 2014 #6

    NascentOxygen

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    If that is a conductive medium of uniform thickness, then the current spreads out in a wide swayth, it doesn't confine its path to a thin middle strip. Think of the block as many resistances all in parallel; current goes through each, though proportionally less through the higher resistance (i.e., longer) paths.
    For DC, picture a block of metal as myriad resistances in 3D. http://thumbnails111.imagebam.com/37333/4d0696373324852.jpg [Broken]
     
    Last edited by a moderator: May 7, 2017
  8. Dec 17, 2014 #7

    davenn

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    thanks for the backup :)
     
  9. Dec 17, 2014 #8

    jim hardy

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    It's like fluid flow. There'll be equipotential lines , segments of a circle centered on corners, with flow largely perpendicular
    I guess that's why in my EE curriculum we had to take a course in Fluid Flow.analysis. Back in those days(slide rules) we worked them graphically like finite elements.
    Only years later did i appreciate the value of that course.
     
  10. Dec 17, 2014 #9


    Very interesting.

    If one was to assume a uniform direction there shouldn't be one right? For such conductors? Current flow will be in all directions?
    I was relating such a design to applications where current has a distinguished impact. Such as the Lorentz force, if it's true that current moves around technically everywhere, there shouldn't be a unified direction. In comparison to the examples where current flow is uniformly obvious?
     
  11. Dec 17, 2014 #10
    Initially, it felt intuitive to assume current flow was all horizontal and some parts we're vertical(around the edges), but if it goes all around... then there shouldn't be a direction for it?
    It makes sense when I think of current being a scalar quantity, but when I apply some calculations, I always mistake it for a vector.
     
  12. Dec 18, 2014 #11

    dlgoff

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    You didn't mention conductors in your OP. Just sayin'
     
  13. Dec 18, 2014 #12
    Whoops! Need to go into details next time!
     
  14. Dec 18, 2014 #13

    sophiecentaur

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    You certainly do - and more precision! I was initially working on the assumption that there were connections along two edges (but which ones?). It would have been much better to have no lines round the edges and a single 'blob' at the corners where the connection is made. Your drawing package will be able to do this for you.
    PF is an untamed beast and will go haring off in all sorts of directions if you don't tell it exactly what to do. Then it's a helpful pussycat.
     
  15. Dec 18, 2014 #14
    . This... the true guidance!

    Hm, I could adjust it now... but I think most of the members who posted get the idea for now.

    But certainly will do in the future!

    How about you give me you're piece about this predicament?
    Why is it a predicament to me? Well, since current is somewhat all around the conductor(Literally...maybe?), does that mean there isn't a unified direction?
    Specifically in relation to Lorentz force, how can it exist if current moving all around the wire?

    Theory headache.
     
  16. Dec 18, 2014 #15

    donpacino

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    While the current does flow throughout all of the conductor, it will still flow from high to low voltage.
    Therefore the general flow of current will be from the bottom right to the upper left.
     
  17. Dec 18, 2014 #16

    sophiecentaur

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    You can also say that the equipotential lines, right next to the connectionswill be arcs of a circle. If the area is a square, (easy bit of symmetry) there will be a diagonal equipotential line across the 'other' diagonal. In the region of that diagonal, the lines will be spaced out more (lower voltage drop because of the lower effective parallel resistance) and tighter together near the connections. The shapes of the lines will morph as you move across the square.
    I just can't remember the book work to do the analysis but the arm waving picture will look as I describe.
    Oh yes - and the current will always flow at right angles to the equipotential lines.
     
  18. Dec 18, 2014 #17
    Great, that makes sense.

    The wording makes sense, yet imaging it is a bit difficult, but eventually I will.
     
  19. Dec 18, 2014 #18

    sophiecentaur

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    Easy peesy. Just imagine emptying a bucket full of tennis balls out at the top of a round topped hill / mound. They will all go in different directions but each one will be rolling 'downhill' taking the steepest path that it can at each point. They will all cross the contour lines at right angles. The electrical equipotential contours are exactly the same.
     
  20. Dec 18, 2014 #19
    Little questions like these remind me of little puzz I still remember from a high school.
    Goes like this: which of fish(es) in a pool will be electrocuted if two HV electric generator wires are submerged in watter at the opposite sides of the pool? Then the picture of fishies swimming in different directions in the pool was given. Anybody else heard of this puzzle?
     
  21. Dec 18, 2014 #20

    dlgoff

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    Here's what the Equipotential Lines for three geometries look like that may help.

    equiv.gif
     
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