Energy Storage in Capacitors

Discussion in 'Homework Help' started by paul_alan, Dec 15, 2011.

  1. paul_alan

    Thread Starter Member

    Nov 5, 2011
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    What is the formula to calculate power in a capacitor circiit?
     
    Last edited: Dec 15, 2011
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    W = 0.5*C*V^2 --> divide both sides by 0.5*V^2

    W/(0.5*V^2) = C

    C = 180J/ (0.5 * 450V^2) = 1777uF

    Q = C*V = 0.8C
     
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  3. crutschow

    Expert

    Mar 14, 2008
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    Just to be clear, W in these equations is energy in Joules stored on the capacitor, not power (which is energy per unit time).

    If the capacitor is being charged and discharged at a specific frequency (f) then the power dissipated in the charge and discharge circuit in watts is f*C*V^2.
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Yep, any R-C snubber used in a switcher has power dissipation in the snubber resistor given by:

    Freq x C x V (squared)

    Doesn't matter what the Ohmic value of the resistor is, same power.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    It's also the power dissipated by an amplifier or digital circuit driving a capacitive load. Charging and discharging the stray capacitance on a circuit board or internally in an IC is the primary cause of power dissipation in CMOS circuits.
     
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