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: Power Dissipated for 2 different circuits

  1. Jul 1, 2012 #1
    Part A:
    For what ratio of R1 and R2 would power dissipated by the resistor of resistance R2 be the same for circuit A and circuit B?

    current for R2 of circuit A is (2EMF)/(2R1+R2)
    current for R2 of circuit B is (EMF)/[(R1^2/2R1) + R2)

    Part B:
    Under which of the following conditions would power dissipated by the resistance in circuit A be bigger than that of circuit B? Choose the most restrictive answer.

    Equations used:
    P = IV = I^2 x R = V^2 /R

    I understand since R and P is same for both i only have to make the 2 currents equal.
    (2EMF)/(2R1+R2) = (EMF)/[(R1^2/2R1) + R2)
    I haven't taken physics or math class in 2 years so I'm kinda unsure on how to continue.
    Since EMF is constant can I just remove it?

    For part B just by plugging in numbers R2>R1 works but im not certain
  2. jcsd
  3. Jul 1, 2012 #2
    Diagram please.
  4. Jul 1, 2012 #3
    totally forgot but here it is

  5. Jul 1, 2012 #4
    deleting my post
  6. Jul 1, 2012 #5
    if i can take out EMF and make R2 = 1 i come out with 4 as my answer. can anyone confirm?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook