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Homework Help: Equivalent resistance

  1. Jun 12, 2009 #1
    1. The problem statement, all variables and given/known data

    I need to find the equivalent resistance of the network outside the battery, and the current in resistor R2. the picture of my circuit is attached.

    R1= 10 ohms
    R2 = 6 ohms
    R3 = 5 ohms
    R4 = 30 ohms

    2. Relevant equations

    series Req= R1+R2...
    parallel 1/Req= 1/R1+1/R2....

    3. The attempt at a solution

    I have a lot of trouble sseing this picture. i think is this:

    R2-4 = 36 ohms
    R1-3 = 1/(.3)= 3.333 ohms
    Req= 36 + 3.33 = 39.333 ohms

    is it right how i split them?

    and would it the current trough resistor 2 just be:

    V=IR 30/6 = 5 Ampere


    Attached Files:

  2. jcsd
  3. Jun 12, 2009 #2


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    So you have R2 + R4 + (R1 || R3) = 39.333 ?
    (I can't see your picture as yet.)

    What is the voltage across the whole thing?
  4. Jun 12, 2009 #3
    when i broke it down in parallel and series, i'm not quite sure if i can assume that R1 and R3 are in parallel. Then i put togheter R4 and R2 as in series and plus R13 in series too..
    but i don't know if i can do that.
  5. Jun 12, 2009 #4


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    Well, since I can't see the picture I'll have to wait. If you don't know whether you can, that is if it is not obviously that way, then ... we'll wait.
  6. Jun 12, 2009 #5
    What's worng with the picture?

    Attached Files:

  7. Jun 12, 2009 #6


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    It's the part that says:
  8. Jun 13, 2009 #7
    so does that mean that my picture is getting approve from someone??
    how long does it take?
  9. Jun 13, 2009 #8


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    The picture is viewable now. Just depends on when someone gets around to approving it. Imageshack is an alternative way to get a jpg up a little faster.

    Looking at your topography, consider redrawing and seeing if you don't find that you have :

    ((R2 || R4) + R3) || R1
  10. Jun 13, 2009 #9


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    Well, it's approved now.
    Imagine an electron travelling from the right side of the battery to the left side. At first, it can either go through R1 or the branch containing R3 (not R3 itself), so R1 is in parallel with the branch containing R3.

    What's the resistance of the branch containing R3? Remember that if the electron passes through this branch, it must pass R3, but after that, it has a choice between R2 and R4. In other words, R2 and R4 are in parallel; R3 is in series.
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