Phasor Diagram

Discussion in 'Homework Help' started by tinhnho, Nov 16, 2004.

  1. tinhnho

    Thread Starter Active Member

    Aug 31, 2004
    hi everyone

    Given V1 = -.41800 - .51918j and V2 = -0.27126 - .35264j
    The question is: " Does V1 lead or lag V2 ? "
    The answer in the book is : Delta_phi = -1.27 degree -- if possitive V1 leads


    My question is how do i know that V1 lead or lag V2 ?

    Thanks everyone
  2. vineethbs

    Well-Known Member

    Nov 14, 2004
    well,first of all V1 and V2 wud be the phasor representations of sinusoidal signals
    in order to find which one leads or lags the other one , u have to find the phase angle between them . Consider the time t=0 for analysis .

    now for both v1 and v2 the real and imag parts are -ive ,so they lie in the third quadrant.
    phase angle of v1 is 180 + arctan(.51918/.41800) = 231.16 deg
    phase angle of v2 is 180 + arctan(.35264/.27126) = 232.43 deg

    now the phase difference is 1.27 deg

    abt the answer in the book :
    Now the phasor difference shows that V2 leads V1 by 1.27 deg

    now as i said before , the phasors aren't fully given , so we don't know whether it is
    v1(or v2) x e^(jwt) or v1 (or v2) x e^(-jwt)

    now if we are taking postive freq or anticlockwise direction of rotation then v2 leads v1 else v1 leads v2 .