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Irms, Vrms and power calculations

  1. Apr 12, 2012 #1
    1. The problem statement, all variables and given/known data

    Basically, I need to understand how to calculate Irms and I*rms given a Vrms and an impedance Z.

    Example question:
    Given Vrms = 120 V at an angle of 30° and an impedance of Z = 10 Ω, find Irms and I*rms.


    2. Relevant equations

    How exactly do I solve for Irms and I*rms?


    3. The attempt at a solution

    I figure that Irms = Vrms / Z. However I am a bit confused as to the I*rms.

    From my notes, I would imply that I just flip the sign of the angle, but this does not seem right.

    My attempt:

    Irms = Vrms/Z = 120angle30/10angle0 = 12angle30
    And for I*rms, just flip the sign of the angle: 12angle-30
     
  2. jcsd
  3. Apr 12, 2012 #2

    gneill

    User Avatar

    Staff: Mentor

    Yup. basically that's it. I* represents the complex conjugate, which for a complex number means that the sign of the imaginary component of the number is inverted. This has the effect of inverting the sign of the angle in polar form.
     
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