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Homework Help: Ac circuit & Power (I)

  1. Mar 18, 2010 #1
    Getting powers from Ac Circuit

    1. The problem statement, all variables and given/known data
    Hi guys,, need help with the following question :

    3. The attempt at a solution
    OK, first things first ,, what does the question mean by saying
    ?? and I know that real power equal I^2 R for series & V^2/R for parallel but the problem it doesn't say if it's series or parallel ,, so my second question is how to start solving the problem ?? (Don't give me answers please just tips :smile: )

    thanks in advance
    Last edited: Mar 18, 2010
  2. jcsd
  3. Mar 18, 2010 #2
    It means that all the inductor is doing is causing a phase shift in the AC source. So the waveform will give an average voltage, current, and even power of zero.

    If you decompose the complex impedance of the inductor you have a real part and an imaginary part. The real power is, just as it sounds, the real part of the power.

    No idea about "power factor."

    Good luck!
  4. Mar 19, 2010 #3
    nice ,, thanks Mindscrape got the idea :smile:
  5. Mar 19, 2010 #4
    "The instantaneous power consumed by the load has zero average value" doesn't mean anything.

    It's a misstatement or something; wrong in one and a half places:

    The average power into the idealized inductive load is zero. The inductive load 'consumes' no power. The instantaneous power can be into or out of the load. Instantaneous power is just the power, positive or negative at any given instant, rather than over the entire AC cycle.
  6. Mar 20, 2010 #5
    no it's useful ,, it's to determine either the real power or reactant power equal zero
  7. Mar 21, 2010 #6
    Instantaneous power and average power are not the same thing. Ask when you are in class.
  8. Mar 23, 2010 #7
    I know they are not the same thing ,, I red in the book that the reactant or real power depends on them ...
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