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Potential applied across two points with batteries

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

    attached

    2. Relevant equations



    3. The attempt at a solution

    The first two were pretty simple, but I'm having trouble grasping why my guess for #3 was actually correct. Why are we ignoring the parallel battery/resistor combo up top and just adding the voltages of the two batteries in series?

    As I understand it, batteries in series do add voltages, so I get that, I just don't understand why that other battery/resistor has no effect.
     

    Attached Files:

  2. jcsd
  3. Sep 30, 2012 #2

    BruceW

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    Homework Helper

    the change in potential is not path dependent. So you can calculate the change using the upper path, or as you have done, using the (simpler) lower path.

    Edit: you can also calculate the change in potential by using a path that goes through E3 then R1, it will still get you the same answer.
     
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