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Electron flow through basic circuit element

  1. Sep 22, 2009 #1
    1. The problem statement, all variables and given/known data
    Given that the current flow is due to electron flow, state whether electrons are entering or leaving terminal 2.
    Code (Text):

       i   _____
      -->  |   |
    - -----|1  |
    v      |   |
    + -----|2  |
           |___|
     
    Situation A: V=40V, i=-10A
    Situation B: V=-60V, i=-10A


    2. Relevant equations
    none.


    3. The attempt at a solution
    My thinking was this:
    Code (Text):

      -10  _____
      -->  |   |
    - -----|1  |
    40     |   |
    + -----|2  |
           |___|
     
    would be the equivalent of:
    Code (Text):

      10   _____
      <--  |   |
    - -----|1  |
    40     |   |
    + -----|2  |
           |___|
     
    meaning that current would be entering 2, and since we have defined current to be positive in the direction opposite the actual flow of electrons that electrons would be leaving 2. The solution doesn't elaborate, but it says that electrons are entering 2.

    B:
    Code (Text):

      -10  _____
      -->  |   |
    - -----|1  |
    -60    |   |
    + -----|2  |
           |___|
     
    would be the equivalent of:
    Code (Text):

      10   _____
      <--  |   |
    + -----|1  |
    60     |   |
    - -----|2  |
           |___|
     
    meaning the same scenario as A, with the exception of voltage polarity. I was under the assumption that the flow of current defined the flow of electrons.
    (using conventional flow notation and the passive sign convention)

    All in all, I'm just looking for a correction of my logic. I doubt the solutions given are wrong, but I suppose it is possible.

    Thanks in advance.
     
  2. jcsd
  3. Sep 23, 2009 #2

    CEL

    User Avatar

    Your solutions are correct.
     
  4. May 17, 2010 #3
    I feel that the current direction shown is with respect to the voltage source positive terminal and not through node 1. In this way, the solution given in the book may be correct. Any ways, your way of thinking and your solutions are also correct.
     
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