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Homework Help: Power output

  1. Feb 21, 2010 #1
    1. The problem statement, all variables and given/known data
    A 580w heater is designed for use in Germany, where electric outlets supply 230V(rms) service. What is the power output of the heater when plugged into a 120V(rms) outlet in the U.S.? Ignore the effects of temperature on the heater's resistance.

    2. Relevant equations


    3. The attempt at a solution
    I tried to fine I(rms) by first calculating for I in germany: I(rms)=(580w)/(230V).
    Then I used this I(rms) to calaulate U.S. power output; barP=(I(rms))(120V).
    This did not give the correct answer.
    Would I have to consider that germany uses DC and U.S. uses AC, is there a conversion for this?
  2. jcsd
  3. Feb 21, 2010 #2


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    Staff Emeritus
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    Homework Helper

    Welcome to Physics Forums.

    Irms will be different in the US than it is in Germany. However, one out of the 4 usual variables will be the same. Question for you: which one?

    (The 4 usual variables are V, I, R, and P.)
  4. Feb 21, 2010 #3
    Btw, Germany does use AC. No country (as far as I know) uses DC as mains.
  5. Feb 22, 2010 #4
    Irms is what I need to find th US power outout, I have no resistance, P is the answer I'm
    looking for, so voltage is the same. I'm lost here how does this help?
    I assumed that Europe used DC because You need different plugs there.
  6. Feb 22, 2010 #5
    Okay after some consideration of the question asked, I figured it out.
    Thanks for all the help'
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