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Homework Help: Combining Series and Parallel Resistor Combinations

  1. May 5, 2012 #1
    1. The problem statement, all variables and given/known data

    Find Rth, at the terminals shown on the diagram

    2. Relevant equations

    Series resistance = R1 + R2 + R3 +....
    Parallel Resistance = 1/((1/R1)+(1/R2)...))

    3. The attempt at a solution

    When attempting problems like this, I was told by teachers and the text book to start at the opposite end of the terminals(where the Rth and arrow is). So in that case I combine the two 6 kohms resistors together (in series), and then combine that with the 3 ohms resistor (in parallel), getting an answer of 2.4 kohms, different to the answer provided.. In the answer provided, they don't start at the opposite end of the terminals, instead they start near the terminals. Is there something I'm not understanding right? or is the answer wrong?

    Attached Files:

  2. jcsd
  3. May 5, 2012 #2


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    Gold Member

    you apparently do not understand the concepts of series and parallel. I suggest that you spend time studying circuit configurations until you can identify what is series and what is parallel.
  4. May 5, 2012 #3


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    Homework Helper

    Remember that the disconnected terminals connected between ends of the 6kΩ resistors can be ignored - you can remove the wire "stubs" on either side of the open circuit completely.

    Also the 3kΩ resistor can be rotated counterclockwise by 90 degrees until it's connected to the wire on top.

    Redraw the circuit in this fashion. Does it look like a much more familiar arrangement?
  5. May 5, 2012 #4
    Ok thanks so much for the help I understand now!
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