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Capacitor Power Dissipation

  1. Feb 14, 2009 #1
    I'm having a really hard time wrapping my head around this. A capacitor in an AC circuit will charge and discharge with respect to the frequency of the signal voltage. Impedance in the circuit is proportional to this frequency and its capacitance. In a power supply the current is regulated through the discharge cycle. What happens to the energy when there is no place to discharge to? Just a capacitive load.....

    "This means that a capacitor does not dissipate power as it reacts against changes in voltage; it merely absorbs and releases power, alternately. " Does this statement mean that all ESR and leakage inefficiencies aside there will be no current in the primary of the transformer beyond the initial charging of the capacitor??????? If this is the case what are the considerations for capacitive loading of a transformer just the initial spike and the inefficiency resistances of the capacitor and transformer??? Does the current through the secondary still limit the capacitive load capabilities??
    Last edited: Feb 14, 2009
  2. jcsd
  3. Feb 15, 2009 #2


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    I'm having a hard time parsing your post, but I believe that, if you were to charge up an (ideal) capacitor, and then disconnect it from the circuit, it'd just sit there waiting to zap the next unwitting victim (yes, we did this with small electrolytics and voltages in undergrad labs--even though the charge is dissipating, there was enough charge to give a small jolt). Many digital cameras use supercapacitors as a make shift battery to keep your settings / pictures while you change your main batteries.

    See also: Leyden Jar:
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