1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook