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Homework Help: Argand diagram, phase difference & power

  1. May 23, 2013 #1
    1. The problem statement, all variables and given/known data
    The potential difference across a circuit is given by the complex number


    and the current is given by the complex number

    I=6+j3 amps

    a) sketch the appropriate phasors on an Argand diagram.
    b) Find the phase difference between the phasors for voltage V and current I
    c)Find the power (watt) given that

    power = VxIxcos∅

    3. The attempt at a solution

    a) Argand diagram attached (I wonder have I maybe took this too literal as it seems too simple?)
    b) tan(V)=35/40=0.875=0.17883 rads
    tan(I)=3/6=0.5=0.46365 rads
    ∅=V-I=0.25518 rads
    so substituting into equation
    (53.151)(6.7082)(0.9676)=345 watts

    Attached Files:

    Last edited: May 23, 2013
  2. jcsd
  3. May 25, 2013 #2
    Your plot for V is backwards on your attachmnet
  4. May 28, 2013 #3
    how so?
  5. May 28, 2013 #4
    Looks like you have V = 35 + j40 plotted. I looks OK.
  6. May 28, 2013 #5
    Ah right thanks for there'll
  7. May 28, 2013 #6
    Silly phone should say reply :-)
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