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Homework Help: Basic Circuit Problem

  1. Mar 16, 2014 #1
    1. The problem statement, all variables and given/known data


    Find voltage across 10 ohm resistor.

    2. Relevant equations

    Ohm's law

    3. The attempt at a solution

    20 // 30 = 12
    30 // 60 = 20

    That's as far as I can get. The answer is 14.286.
  2. jcsd
  3. Mar 16, 2014 #2


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    Staff: Mentor

    While the 20 and 30 Ohm resistors are in parallel, the 30 and 60 Ohm resistors are not (the voltage source intervenes).

    You'll need to pull out some circuit analysis method. There are several choices. What methods have you studied so far?
  4. Mar 16, 2014 #3

    Here's the solution to the problem.

    It looks like the book did source transformation, which I didn't think was fair because this problem is before source transformation.

    I know nodal analysis and mesh but I thought it was possible to do without them. I thought you could just find the R-total and then you could find the total current. I guess not?
  5. Mar 16, 2014 #4


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    Staff: Mentor

    Yup, they did a source transformation (Norton) and then current division.

    You need more than simple resistor network reductions (parallel/serial) here. Nodal analysis would be a good choice.
  6. Mar 16, 2014 #5
    alright thanks
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