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Finding complex power in AC circuit

  1. Oct 31, 2015 #1
    In a branch I have to find complex power which is having current 19.41<-37.3 A and impedance 4+j3 Ω
    What I used is i2z and I was getting 1489.85 - j1152.74 W.
    This is wrong but I don't know how because by this site the answer was different
    http://www.rapidtables.com/calc/electric/power-calculator.htm
    Can someone tell me what is wrong going on?
     
  2. jcsd
  3. Oct 31, 2015 #2
    Is this a homework problem?
     
  4. Oct 31, 2015 #3
    No the homework problem was something other. When I was doing it in middle this query araised. I just want to ask the concept that when impedance is given and current is given, the complex power should be Vi or i2z, isn't it?
     
  5. Nov 1, 2015 #4

    Henryk

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    Gold Member

    The voltage is give as ## V = I * Z = I * Re(Z) + I * Im (Z) ##. The second term is 90 degrees out of phase with respect to current. The average power dissipated is then ##I_{RMS}^2 * Re(Z) ##
     
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