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Finding the Potential at a specific point in this Circuit

  1. Jul 25, 2014 #1
    1. The problem statement, all variables and given/known data
    Here is the circuit: http://gyazo.com/1e11d9208da0aa29d10b72128844ad40
    What is the Electric Potential at Point A?
    Battery 1: 6.76 V
    Battery 2: 11.8 V
    Resistance 1: 100Ω
    Resistance 2: 217Ω
    Resistance 3: 312Ω



    2. Relevant equations
    Kirchhoff's Rules
    V=IR


    3. The attempt at a solution

    I first set up my Currents so that Current 1(left)+ Current 2(down middle)= Current 3(right)

    Let c be left of point a, b the point bottom of point a, d left of b, e right of point a and f right of b.


    cabdc: -217(Current 1)+100(Current 2)=-6.76
    =-217(Current 1)+100(Current 2)

    aefba: -312(Current 3)-11.8-100(Current 2)=0
    =-312(Current 3)-100(Current 2)=11.8

    Let Current 2= Current 3-1

    So..

    -217(Current 1)+100(Current 3-1)=-6.76

    -312(Current 3)-100(Current 3-1)=11.8

    And I get

    312(Current 3)-217(Current 1)+200(Current 3-Current 1)=-18.56

    I'm stuck at this step, could use some help.

    Thanks.
     
  2. jcsd
  3. Jul 25, 2014 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    It is difficult to spot errors (and easy to make them) when working without a diagram. But the two statements below seem to lack compatibility. Check the signs/directions you are using.

    cabdc: -217(Current 1)+100(Current 2)=-6.76
    Current 2= Current 3-1
     
    Last edited: Jul 25, 2014
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