A capacitor of C farads with V volts across its terminals will contain Q coulombs of stored charge.

Q = CV

The energy stored in a capacitor is equal to the work done to charge it,

U = 1/2CV2,

where stored energy U is in joules.


Anode ----| (---- Cathode.  Anode indicated with + sign, long lead or band.  Cathode indicated by - sign, short lead or arrow.

In Series

Ctotal = (C1 x C2)/(C1 + C2); Qtotal = V(C1 x C2)/(C1 + C2)

In Parallel

Ctotal = C1 + C2; Qtotal = V(C1 + C2)


5RC Rule of Thumb:  A capacitor charges or decays to within 1% of its final value in 5 time constants.

The Time Constant, t seconds, of an RC circuit is the product of its resistance, R ohms, and capacitance, C farads,
t = RC.

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Page author: Dawn Rorvik (rorvikd@evergreen.edu)
Last modified: 05/20/2003