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Effective Resistance of a circuit

  1. Oct 14, 2011 #1
    1. The problem statement, all variables and given/known data

    Revered members,
    I need to find the effective resistance of this circuit which i have given in attachment.
    circuit.


    2. Relevant equations



    3. The attempt at a solution
    Now let me explain how i carried out.
    I proceeded from right to left
    1) R s = 12 + 6 = 18Ω
    2) Rp = R1 R2/R1 + R2 which is (18 x 6)/24 = 4.5Ω
    3) R = R1 + R2 = 18 + 4.5 = 22.5Ω
    I have given the above steps in my second attachment
    Now, for the same problem when i proceed from left to right
    1) I took 18Ω and 6Ω as parallel i got 4.5 Ω and then this 4.5 is in series with
    12 Ω and 6Ω so 4.5 + 12 + 6 = 22.5Ω
    I have given the above steps in my third attachment
    Now my question is why should not i take 18 Ω and 6Ω as series connection and proceed, because when i take those 18 Ω and 6Ω as described in my last attachment in the following reply,
    i get wrong answer. Where do i go wrong?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Oct 14, 2011 #2
    continuing my previous query, this is my last attachment. Is this not a series circuit? But when i take this as series and proceed from left to right, i get wrong answer.
     

    Attached Files:

  4. Oct 14, 2011 #3

    lewando

    User Avatar
    Gold Member

    Because, in the first image, they are not in series. You were correct in proceeding from right to left (2nd image).
     
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