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Converting to a circuit's Thevenin equivalent?

  1. Feb 5, 2017 #1
    1. The problem statement, all variables and given/known data
    9e394656-9726-3863-a477-3e151818d431___18b248a0-12e1-3001-8982-625d7321b1c6.png

    2. Relevant equations
    Finding the Thevenin equivalent?

    3. The attempt at a solution
    I found the thevenin resistance to be 185/47 ohms, which came out to be correct.

    I've been struggling with this question all day. I ended up attempting to find the norton equivalent and then converting it, since the question asks for both anyways. I started with a source conversion on the 3A and 5ohm current source and resistor, turning it into a 15V voltage source and a 5 ohm resistor in series (going into the b terminal). I shorted the a-b terminal and used KVL to find the current going through as 3A, typed that into my webwork page and it said I was wrong. Is there anything I'm missing here?
     
  2. jcsd
  3. Feb 5, 2017 #2

    gneill

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    Staff: Mentor

    Are you given values for ##I## and ##R## ?
     
  4. Feb 5, 2017 #3
    Oh yeah sorry, I = 2.5A and R = 4.5ohms
     
  5. Feb 5, 2017 #4
    On that note actually, these problems look fairly straightforward and I'm afraid that I misunderstand something fundamental about circuits...
     
  6. Feb 5, 2017 #5

    gneill

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    Staff: Mentor

    Okay.

    Hint: Work from left to right towards the output, converting and combining sources and resistances as you go.
     
  7. Feb 5, 2017 #6
    If I have a voltage source>resistor>voltage source>resistor in series could I just rearrange and combine them? If so I converted the leftmost current source and resistor to a voltage source in series with it, combined the 2 resistors and voltage sources to get 25.25V and 18.5 ohms. I converted those to a current source in parallel with a resistor to get 101/74A and 18.5ohms. Adding those to the current source in parallel with the resistor on the right I get 121/74A (pointing down) with 185/47ohms, giving me a voltage difference of 605/94 but the program says that is incorrect...
     
  8. Feb 5, 2017 #7
    Oh my god it explicitly wanted the voltage from a to b, and that is -605/94. I've been trying to figure this out for four hours... Thank you for the help haha.
     
  9. Feb 5, 2017 #8

    gneill

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    Staff: Mentor

    :smile:
    Glad to help!
     
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