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Homework Help: Power and current

  1. Apr 10, 2007 #1
    1. The problem statement, all variables and given/known data
    An electric current described by I = 12 sin(250t) flows through a 20 ohm resistor. Calculate the power dissipated as heat.

    2. Relevant equations
    P = I^2*R

    3. The attempt at a solution
    Using the last equation, P = I^2*R
    P = 2880 sin^2(250t)
    Is that the best answer I can give? The question gives no information about efficency so I'm not sure if I'm forgetting an equation or something. It doesn't give a value for time either.
  2. jcsd
  3. Apr 10, 2007 #2
    I think you misinterpreted the problem. The problem asks for the power dissipated as heat, not the power in the element.
  4. Apr 11, 2007 #3


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    Gold Member

    You need to integrate over a time period then divide by the period to get the root mean square (rms) value.
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