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A simple question about current and voltage

  1. Jan 11, 2008 #1
    I'm sorry guys but i just couldn't go through all the previous topics to find out if my question has been answered before...Its not a homework related question or anything but just a thing that has been buzzing me..I'm in my first year in electrical engineering.

    I think that before any current flows in a branch of a circuit, it knows which path its going to take and how many is going to flow in branch A and how many is going to flow in branch B......am I right about this?

    If I am then is this due to voltage which i think of as the "drawing power" of the current in the circuit...is this also right?

    many thanks guys, this is my first post and i'm glad I found this forum.

  2. jcsd
  3. Jan 11, 2008 #2


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    Staff: Mentor

    No, it's more like a Pachinko machine:


    Where gravity supplies the accelerating force (like the voltage), and the balls fall down through various paths, encountering different amounts of resistance based on how many pins are in the way, and how much the balls back up against the various resistive paths....

    Does that help?
  4. Jan 11, 2008 #3
    but when the current encounters branching what determines how many will go in which branch...i know of course its the resistance but "the current" doesn't...

    and so voltage IS after all the drawing power or the driving force of the current right?

    thanks for the incredibly quick reply
  5. Jan 11, 2008 #4


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    Staff: Mentor

    Look at the way the balls bunch up and slow down when they encounter a higher resistance in the various Pachinko paths. I think that's the best visual analogy that you'll get as to why some balls seem to "prefer" the lower resistance path -- they bounce off of the backed up balls at the top of the high resistance path, and end up falling down the easier path more quickly.

    Don't worry too much more about it -- get a little farther into your studies before worrying about more visualizations. It would help for you to get some solid state physics under your belt before spending much time thinking about the Pachinko analogy. It's better to have the real solid state model in your head instead. How long until you get to your first solid state physics class?
  6. Jan 11, 2008 #5
    I'm not sure but the thing is that i predict the behaviour of the circuit just by looking at it, thus i wanted to be sure that i make correct assumptions. Thank you once more
  7. Jan 11, 2008 #6


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    Gold Member

    I think asking a question on the basis of how an electron or current "knows" something about its physical environment will only lead to much confusion (this has happen to me lots of times). The mathematical models that describes these physical systems does not address how an object "knows" something. And why would there be any need for that? After all, we only need to understand the behavior of our subject of interest under certain circumstances.

    You have already answered your question, by stating that the parameter is resistance (or conductance). What else is there?
  8. Jan 11, 2008 #7
    well as i said, given that the current never passed through the whole circuit and it goes in a wire then it faces a branching, what determines which branch it goes through and by how much....again as i said i know its resistance but what i mean is the when current is flowing in a wire does "sense" that there is resistance in this whole branch and there's less resistance in the other and thus it goes through the late branch.

    I know what is resistance but what IS it anyway? we view it as a coil and thus gives you the visual of a coiled wire, and the more wire there is the more the resistance..I know its a shame on me that i'm a university student and am asking these silly questions but its never a bad idea to ask a question after all.

    and if u have some time, can u look at a question about quantum mechanics?


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