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

Power transferred to resistance

  1. Jun 29, 2011 #1
    1. The problem statement, all variables and given/known data
    Speaker Resistance = 10.4 Ohm
    R = 8.20 Ohm
    Maximum voltage of AC source = 15.0 V

    What's the average power transferred to the speaker?

    2. Relevant equations

    P = [itex]I^2R[/itex]
    Imax = [itex]I/2^0.5[/itex]

    3. The attempt at a solution

    I could the problem if there was only the speaker resistance. I don't understand how the other resistance comes into play or what it does in the circuit.
  2. jcsd
  3. Jun 29, 2011 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi Tosh5457! :smile:
    The extra resistance reduces the current, I. :wink:
  4. Jun 29, 2011 #3


    User Avatar

    Staff: Mentor

    The other resistance, in series with the speaker resistance, form a voltage divider. Only a fraction of the supply voltage will appear across the speaker resistance.

    You can determine the current through the series connected resistors, then using that current find the voltage developed across the speaker.

    Keep in mind that you've been given the maximum voltage of the AC source. To find the average power you'll want the RMS values for voltage and current delivered to the speaker.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook