Confused over this Series-Parallel Circuit

Discussion in 'Homework Help' started by thakid87, Oct 29, 2009.

  1. thakid87

    Thread Starter Active Member

    May 23, 2009
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    Hello all.

    Attached is a copy of a circuit that I am having an issue with.

    According to my textbook, total resistance is 852 ohms, but I am getting a calculation of 574 ohms.

    Can anybody show me where I am going wrong?
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    I also get Rtot=573.76Ω, which is close enough to your answer. Did you transcribe the circuit exactly as shown? If so the book is wrong.
     
  3. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    When redrawn, the circuit looks like the attachment and is closer to the textbook answer.
     
  4. t_n_k

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    Mar 6, 2009
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    Huh? That's not the OP's question.
     
  5. Thav

    Member

    Oct 13, 2009
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    It is, but the reference designators come are a little close to the values so it's hard to read.

    I get 851.7 by doing the two parallel combinations on the right hand side, combining those in series, then doing the parallel combination of the left and right hand side.
     
  6. yasir_66

    Active Member

    Jun 25, 2009
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    your book answer is correct i also verified as i get Rt=851.8 ohms.
    Resolve your circuit may be you making mistake in observing diagram.
    Note that R2 & R5 is in parallel & R3 & R4 also in parallel.
    Then add R25 & R34 as this is in series & finally it is again paralleled with R1
    your final calculation should be in using parallel formula for R1 & R2345.
     
  7. hobbyist

    Distinguished Member

    Aug 10, 2008
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    doesn't the R1, get shorted by the volt. source being shorted?

    What terminals, are the resistances being measured from? (left side or right side of circuit)
    I'm assuming right side.
     
    Last edited: Oct 30, 2009
  8. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    Agreed - my error as well. Sorry for the distraction.
     
  9. Thav

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    Oct 13, 2009
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    I assumed we were talking about the equivalent resistance seen as a load to V1.
     
  10. JoeJester

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    Apr 26, 2005
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    I assumed it was the total resistance (load) across V1.

    I started at the negative terminal and imagined how the current flowed to the positive terminal of the voltage source.
     
  11. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    There was no indication by the OP this was a thevenin problem. If there were, the output nodes would have been identified.
     
  12. hobbyist

    Distinguished Member

    Aug 10, 2008
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    yeh, your right.

    I was so use to seeing all those thevinin questions, that I completely overlooked the obvious, that this is a basic solve the resistance that the volt. source sees. [​IMG]
     
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