Total resistance + Thevanin problems

Discussion in 'General Electronics Chat' started by Dritech, Nov 11, 2012.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Hi all,

    I have some problems regarding total resistance and Thevenin.

    Problem 1:

    In the first attachment, is the 2ohms in parallel with the 6ohms, total in parallel
    with the 8ohms and the total in series with the 10ohms ??

    Problem 2:

    In the other attachments I am trying to find I load using Thevenin theorem, but the current is not matching with the correct answer. Does anyone know what am i doing wrong?

    Please help.
    Thanks in advance and sorry for my poor English.
     
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  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    Problem 1:

    2Ω resistor is short by the wire.

    Problem 2

    I got the same answer as you
     
    Last edited: Nov 11, 2012
  3. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Thanks for the reply.

    Does that mean that i have to ignore the 2 ohms (i.e. 6 in parallel with 8, result in series with 10 ??
     
  4. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    Yes, exactly you shoudl ignore 2Ω resistor.
    And as you said Rtot is equal Rtot = 10Ω + 6Ω||8Ω
     
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  5. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Hi again,

    I have the attached circuit with parallel and series resistors. Are they as follow:

    12//18 --- result//10 ---- result2//22 ---- result3 + 15 ??
     
  6. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    And in this circuit are the 22 + 15 .... result//18 .... result2 + 12 + 10 ???

    PLEASE HELP.
     
  7. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    Resistance seen from this current source terminal is equal to
    Rtot = ((22+15)||18) + 12 + 10 = 34.109R

    And resistance seen from 48V voltage source terminal is equal to

    Rtot = 22 + 18 + 15
     
  8. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Thanks for the reply

    And what happen with the 12 and 10 resistors please?
     
  9. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    The 48V source current can flow only in closed loop. So how can he flow via 12 and 10 where we have a open circuit?
     
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  10. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Ok. Thanks for your fast reply :)
     
  11. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Hi again,
    can someone tell me how to work the total resistance of the attached circuit please ?
     
  12. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
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    If I work it as below, is it correct?

    ((R1//R2)//R3) + (R4//R5)
     
  13. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    Well, between which terminals you want to find this total resistance?
    Also you can always use delta-wye transformation.
     
  14. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Hi Jony130,

    I want to find the total resistance from the terminals of the load resistor which is marked in red in the picture attached below. I removed the load resistor since i meed to find the current on each resistor using Thevenin theorem (so I think I cannot use delta to star transformation)

    Thanks in advance.
     
  15. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    If so I think that Rtot = R3||(R1||R4 + R2||R5)
     
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