Leading and lagging waveforms

Discussion in 'Homework Help' started by daunus, May 7, 2009.

  1. daunus

    Thread Starter New Member

    May 7, 2009
    1
    0
    Hi Im new to these forums but hopefull ill hang around for a while,


    Determine which waveform in each pair is lagging and by how much


    a)6cos(2pi60t-9°) & -6cos(2pi60t+9°)

    b)cos(t-100°) & -cos (t-100°)

    c)700cos(t-pi) & 700cos(t-3.14°) ---- here I think first waveform laggs by 176.86 °


    does a negative amplitude make any diffrence?
     
  2. SawabyPlus

    Member

    Feb 27, 2009
    14
    0
    phase written between the parentheses may be misleading if the amplitude is not +ve, for real systems of course.
    you should just drop the sign and add a phase of +/-pi to compensate. put the resultant phase in the principal form. and u know the rest, like you've done in part c.
     
  3. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,039
    287

    Yes....this is why there is always a phase ambiguity problem with things like phase locked loops....is it leading by 90 or lagging by 270?

    Eric
     
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    The minus sign means that the waveform is also shifted by 180 degrees because cos(θ+180)=-cos(θ).

    Thus

    -Acos(ωt+θ)=Acos(ωt+θ+180)
     
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