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Potential difference between points d and c in circuit

  1. Dec 1, 2016 #1
    1. The problem statement, all variables and given/known data
    In the figure below, what is the potential difference Vd - Vc between points d and c if E1(of 1st battery) = 4.7 V, E2((of 2nd battery) = 1.4 V, R1 = R2 = 11 Ω, and R3 = 6.7 Ω, and the batteries are ideal?
    http://farm6.static.flickr.com/5053/5469093809_53c7fe57f4.jpg

    2. Relevant equations
    V= IR
    3. The attempt at a solution
    I used superposition in order to find the current at R2 which leads to V2 = I2R2.
    I separated the circuit into two circuits , each with one battery and its own calculations then I added them together , but the final answer seems wrong for an unknown reason....
    https://scontent-sin6-1.xx.fbcdn.net/v/t35.0-12/15302523_1489883864359796_661161770_o.jpg?oh=7c4c036aa34ea2f78ce415299ea1557d&oe=58425946
     
  2. jcsd
  3. Dec 1, 2016 #2

    gneill

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    Staff: Mentor

    What is the direction of flow of the final current? Will it cause a potential drop or a potential rise between node d and node c?
     
  4. Dec 1, 2016 #3
    There's 3 circuits...
     
  5. Dec 1, 2016 #4
    The current flow as mentioned is upward on R2.
    I tried puting -0.3 v and 0.3v , both were wrong.

    There are only two batteries and 3 resistors.
     
  6. Dec 1, 2016 #5

    gneill

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    Staff: Mentor

    Yeah, you'll probably want to conserve more digits through your intermediate calculations.
     
  7. Dec 1, 2016 #6
    But my steps are right , are not they ? I will do it using less rounding this time.
     
  8. Dec 1, 2016 #7

    gneill

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    Staff: Mentor

    Your steps looked fine when I scanned through your work.
     
  9. Dec 2, 2016 #8
    Yes, but the two batteries are in series with each other, forming a circuit with R1 & R2
     
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