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Homework Help: Complex power for RL and RC

  1. Apr 17, 2014 #1
    Is this true?

    Or is this true?

    Ø and Q are from this equation:
  2. jcsd
  3. Apr 17, 2014 #2


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    Staff: Mentor

    You can play with a few numbers to confirm or refute the statements. Here's how.

    Suppose you assume a source voltage of E = 2V RMS. Set your impedance to a convenient value like Z = 1 + 1j Ω for an RL load, or to Z = 1 - 1j Ω for an RC load.

    Now, a very handy formula to know is that the complex power is given by S = EI*, where I* is the complex conjugate of the current I (the sign of the imaginary term is reversed). You can determine the current for your sample values as I = E/Z. Plug in the values and see how the various signs and angles turn out.
  4. Apr 17, 2014 #3
    Thanks a lot
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