How to find circuit total resistance?

Discussion in 'Homework Help' started by Excedrin, Feb 3, 2011.

  1. Excedrin

    Thread Starter New Member

    Feb 3, 2011
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    Hi, I'm having a tough time figuring the total resistance of this simple circuit. MultiSim 11.0 says that the resistance is 937.83 Ohms. I don't get how it came up with that value. Can anyone help me with how to figure this one out? MyCircuit.jpg
     
  2. Tera-Scale

    Active Member

    Jan 1, 2011
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    5
    Is one of the 'measuring' terminals grounded as well?
     
  3. Excedrin

    Thread Starter New Member

    Feb 3, 2011
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  4. Excedrin

    Thread Starter New Member

    Feb 3, 2011
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  5. Excedrin

    Thread Starter New Member

    Feb 3, 2011
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    I posted the full circuit image including ohmmeter placement and ground. Thanks for looking.
     
  6. Heavydoody

    Active Member

    Jul 31, 2009
    140
    11
    I come up with 937.830499 using nodal analysis. I applied an arbitrary voltage to the network and came up with four equations for the four unknown nodes. Then I used a simultaneous equation solver. The difference in voltage across the 500 ohm resistor divided by 500 is total current. The arbitrary voltage divided by that current is the resistance.
     
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  7. narasimhan

    Member

    Dec 3, 2009
    72
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    It's a simple resistor circuit. The answer is 937.83 ohms. Actually 937.830499 ohms to be precise.
    No need to use nodal analysis.
    Use delta-wye conversion in any one of the two deltas and the figure gets siplified to just series and parallel resistances.
     
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  8. Excedrin

    Thread Starter New Member

    Feb 3, 2011
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    Thank you so much! That was awesome!! I'm such a noob at this stuff and I have been trying to wrangle (unsuccessfully!) this seemingly simple circuit for hours by trying to redraw it into more obvious series-parallel equivalencies.

    I see that Delta-to-Wye conversions is coming up in the next chapter, and Node Analyses is the chapter after that, so I guess I'll just table this problem until then. Nodal and mesh analysis was mentioned by my teacher as probably needed, but I didn't have a clue what he was talking about. Now I'm totally motivated to get on to the next couple of chapters.

    So thanks again guys!! :D
     
    Last edited: Feb 3, 2011
  9. narasimhan

    Member

    Dec 3, 2009
    72
    6
    Your welcome. good to see people interested in electronics. wait and see bjt and fet equivalent circuit analysis will be even more interesting.

    by the way for this circuit delta wye is the best. you'll get answer within a minute using paper and pencil(and calculator if needed for precision division).
    nodal and mesh will be more useful if some voltage or current of a branch needs to be calculated. For this circuit it'll take more than a few minutes to solve using nodal or mesh.
     
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