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Homework Help: Equivalent Resistance

  1. Feb 15, 2010 #1
    1. The problem statement, all variables and given/known data
    Find the equivalent resistance between points a and b in the figure

    2. Relevant equations
    1/Req = 1/R1+1/R2... for parallel
    Req= R1+R2... for series

    3. The attempt at a solution
    12.63 ohms

    Attached Files:

  2. jcsd
  3. Feb 15, 2010 #2
    If you show your work, we can spot your errors and guide you. Or are you just asking if your answer is right?
  4. Feb 15, 2010 #3
    I have that the 4 and 2 ohm resistor are in series and add to be 6 ohms equivalent resistor. The 6 ohm resistor and the 3 ohm resistor are parallel and 1/6+1/3=1/2 or 2 ohms equivalent. I don't know what to do next though. Are the 1, 2, and 10 ohm resistors in series?
  5. Feb 15, 2010 #4


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    No. If two elements are in series, all the current that goes through one has to go through the other. A current flowing through the 10-ohm resistor can go through the 9-ohm resistor or the 2-ohm resistor, so the 10-ohm resistor and the 2-ohm resistor are not in series. In contrast, all of the current in the 2-ohm resistor must also go through the 1-ohm resistor, so those resistors are in series.
  6. Feb 16, 2010 #5
    Try re-drawing the circuit with your new values ... it may become clearer that way. Sometimes, it helps to re-draw the circuit vertically: in your case with "a" at the top of the diagram and "b" at the bottom.
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