Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

2 Resistors in Parallel versus in Series

  1. Aug 19, 2010 #1
    1. The problem statement, all variables and given/known data
    Two resistors when connected in series to a 110 V line use one-fourth the power
    that is used when they are connected in parallel. If one resistor is 2.0 kΩ, what is the resistance of the other?

    2. Relevant equations


    3. The attempt at a solution






    snce x= 1560

    the value of another resistance is 1.56 kilo ohm

    Did I do that right?
  2. jcsd
  3. Aug 19, 2010 #2
    Not quite. Okay, your series formula is fine. But now you have to get the power for the resistors in series. P=I^2 R and P=V^2/R.

    Now that you have the power for the series resistors, find the power for the resistors if they were in parallel. 110=i*Req again, but different Req this time.
  4. Aug 19, 2010 #3
    Can I just cancel the V's out and solve like this:

    R2 + 2000 = 2*(2000*R2)/(2000 + R2)

    Which looks like it would require the quadratic eqn
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook