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Homework Help: Variable resistance

  1. Feb 7, 2007 #1
    1. The problem statement, all variables and given/known data
    "A circuit has a variable resistance (total 100 ohms) across which is a voltage drop of 12 V supplied by a battery. What must be its resistance if the voltage is to be A) 12V and B) 6.2V?"

    2. Relevant equations

    3. The attempt at a solution
    We haven't learned anything besides Ohm's Law for these equations, so I tried plugging in different values to try and dial in the answers, but it didn't work. Is there something I'm missing or am I being asked to solve for two unknowns? Hints appreciated.
  2. jcsd
  3. Feb 7, 2007 #2
    Is that all you have? Diagram? Im assuming total resistance is 100 ohms so for 12 v you have 8.5 amps. Then for 12V, you need a resistance of 12/8.5 but I dont trust this answer. If its a serial pair of resistors where Rx and Ry are 100 ohms and you are being asked the voltage drop across Rx, i think the above is good.
    Last edited: Feb 7, 2007
  4. Feb 7, 2007 #3
  5. Feb 7, 2007 #4
    drawing a blank on the diagram, literally
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