power in out of phase circuits

Discussion in 'General Electronics Chat' started by paul_alan, Dec 6, 2011.

  1. paul_alan

    Thread Starter Member

    Nov 5, 2011
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    I'm just starting to work on power in AC CIrcuits. And i'm not understanding this question;
    true or false: a current that leads a voltage source by 30° uses more power than a current that lags it's voltage source by 30°.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,009
    3,233
    The question is simple. It's more likely the answer that you are having a problem with.:rolleyes:

    So does a leading power factor of a given angle use more power than a lagging power factor? If you know the equation for calculating real power based upon the phase angle then you can determine the answer.
     
  3. who_me_yes_you

    New Member

    Dec 7, 2011
    8
    0
    Real power = V*I*cos[angle between current and voltage]

    considering the above equation, because the values of [cos 30] and [cos-30] are the same, then the amount of real power dissipated will be the same regardless of whether voltage leads or lags current.

    (The phase angle relates to whether the circuit is capacitive or inductive in nature...)
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,009
    3,233
    Aw, you spoiled the fun and told him the answer.:rolleyes:
     
  5. who_me_yes_you

    New Member

    Dec 7, 2011
    8
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    Sorry for being a spoil sport!
     
  6. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    What kind of "power"?

    There are actually three different types of "power" used commonly in electronics:

    1) Watts (true power)

    2) VA (Volt-Amps)

    3) VARs (Volt-Amps Reactive)

    If you undertsnad these and what the differences are, you will know the answer. Read:

    http://www.allaboutcircuits.com/vol_2/chpt_11/2.html
     
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