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Homework Help: Phasor circuit

  1. May 2, 2010 #1
    Hi,

    I have the following circuit
    [PLAIN]http://img707.imageshack.us/img707/3024/upgp580.png [Broken]

    And i need to find the phasor current I, the power, reactive power and apparent power delivered by the source and state whether it's lagging or leading. But im kind of stuck at the first step.

    First i replace the capacitor with it's complex impedance
    [tex]-j\frac{1}{333\cdot10\cdot10^{-6}} = -J300.3[/tex]

    And that is parallel with the 115ohm resistor, yielding:

    [tex]\frac{1}{(1/115)+(1/-300)} = 186.48\ohm[/tex]

    And the phase angle

    [tex]arctan\bigg(\frac{1/-300}{1/115}\bigg)= -20.93 [/tex]

    So the current I is given by
    [tex]\frac{1585\sqrt{2}}{186.48} \cdot cos(12-(-21)) = 10.08[/tex]

    Which is as usual incorrect.
    According to the key the current I is [tex]15.11 \angle 20.66[/tex]

    Please help
    James
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. May 17, 2010 #2
    You should consider capacitive reactance as a complex quantity while calculating total impedance.
     
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