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Homework Help: Resistance circuit problem

  1. Nov 8, 2013 #1
    1. The problem statement, all variables and given/known data

    Hi, this was an extra credit problem on a test I had that I think I remember correctly


    Given R find R equivilent of the circuit

    2. Relevant equations

    Series R1, R2 = R1 + R2
    parallel R1, R2 = (1/R1 + 1/R2)^-1

    3. The attempt at a solution

    Never encountered a resistor in an awkward spot as the middle is, so I tried saying this:

    since the upper path to Vb is an open wire it has Vo and the bottom path much match. To do this the voltage across these two must be 0 so we can just ignore them. From there you just have a parallel set left so

    1/R + 1/2R = 3/2R -> 2R/3 = Req
    Last edited: Nov 8, 2013
  2. jcsd
  3. Nov 8, 2013 #2


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    Staff: Mentor

    Hi oreosama. From the left end of that 2R resistor, I see two parallel paths to get to point b.
  4. Nov 9, 2013 #3
    ive always understood parallel/series as a visual type thing. youre saying 1/R + 1/3R = 4/3R -> 3R/4 ? I Have no idea what this does to the circuit, as in where this combined resistor would be.. relative to the middle one still standing
  5. Nov 9, 2013 #4


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    Staff: Mentor

    I suggest that you redraw the circuit, drawing that middle resistor so this its symbol, too, is horizontal. Then connect the ends so electrically the circuit is identical with what you are given. Now, tidy it up so it looks like a neat circuit.

    You might need to do this a couple of times, before you see how it simplifies.
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