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Power dissipation in inductors

  1. Sep 1, 2009 #1
    I have found a possible mistake in my book....here's the text which contains it,

    "Referring to figure, it can be seen that no power is disspated in a pure inductor. In the first quarter of cycle, both V and I are positive so the power is positive, which means that energy is supplied to the inductor. In the second quarter, V is positive but I is negative. Now power is negative which implies that the energy is returned by the inductor......"
    (The figure looks "something" like this) ::
    http://img25.imageshack.us/img25/485/grapha.png [Broken]

    Isn't V negative and I positive in the 2nd quarter according to the figure?
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 1, 2009 #2
    The author is incorrect; I is positive and V negative in second quadrant. If the integrated area per cycle is zero, then there shouldn't be any dissipated power. Integrate sin(wt) * cos(wt) over 2 pi radians, and determine what the area is.
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