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Multiple Resistors and Short Circuit

  1. Jan 30, 2012 #1
    1. The problem statement, all variables and given/known data

    This is more of a concept question rather than a HW problem, but I have two Circuits shown in the image attached. I am not really understanding how a short would affect resistance in these cases.

    2. The attempt at a solution
    For figure 1 I am considering one of two possibilities:
    1) Req = (R1 || R2) + (R3 || R4)
    2) Or there simply is no equivalent resistance b/c the entiretly of the current wants to travel down the short and this creates a contradictory circuit

    And for figure 2 (redrawn to the right) I am considering one of two possibilities:
    1) Req = (R1 || R3) + (R2 || R4)
    2) Or there simply is no equivalent resistance b/c the entiretly of the current wants to travel down the short and this creates a contradictory circuit (same as above)

    Anyway if anyone could point me in the right direction that'd be great.
    -Thanks!
     

    Attached Files:

  2. jcsd
  3. Jan 30, 2012 #2

    epenguin

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    Homework Helper
    Gold Member

    I'd say your 'redrawn to the right' fig is 1, not 2 redrawn.

    I have not met before the notation you are using but it seems fairly self-explanatory and it looks to me 1.1 is right.

    A short means the two nodes connected by it are at the same potential, so it will be clearer to you if you redraw (even mentally) with the shorted nodes fused into one, then it's very simple I hope.

    For 2 I understand the nodes are not connected at the 'waist'. So then you have one branch with two in-series resistors and its resistance is their sum, then the same on the other side....
     
    Last edited: Jan 30, 2012
  4. Jan 30, 2012 #3
    thanks for the quick reply.

    So for figure 2 the resistors I have circled in blue would be in series?
     

    Attached Files:

  5. Jan 31, 2012 #4

    NascentOxygen

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    Staff: Mentor

    correct

    correct

    When schematic is not clear, keep redrawing it until it becomes clear. This may take multiple trials. Do not draw multiple parallel connecting wires; combine them into one wire.
     
  6. Jan 31, 2012 #5

    NascentOxygen

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    Staff: Mentor

    no they would not be
     
  7. Feb 6, 2012 #6
    no two resistors are in series here
    there are two pairs of resistors, each pair contains two resistors in parallel, the two pairs are then in series
    Figure 1 and 2 are the same, only the subscripts for which resistors are parallel will change, otherwise the basic structure of the circuit in both cases is the same
     
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