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Fundamental Capacitance Equation

q = C V
Differential Form: I = C \frac{dV}{dt}

The Equivalent Capacitance of Series Capacitors

C_{eq} = \frac{C_1 C_2}{C_1 + C_2}

Note also, that the charge into the equivalent capacitance is equal to the charge into each capacitor in the series.

The Capacitive Divider Formula

When two capacitors are in series, and the voltage at one end changes, the voltage at the shared node can be computed be calculating the charge injected into the equivalent capacitance and then the change in voltage across each capacitor when the same charge is injected into them. For a pair of capacitors, when one end (C2) is grounded and the voltage at the other end (C1) changes, the voltage at the shared node is:

\Delta V_{shared} = \frac{\Delta Q_{eq}}{C_2} = \Delta V_{in} \frac{C_1}{C_1 + C_2}

See Also: The Voltage Divider Rule ,Symbols

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Last edited by DrLock. Originally by DrLock.