A series combination of capacitors is reduced to a single capacitor by adding the sum of the inverses of each individual capacitor, then inverting that. The equation is C_eq = (1 / ((1 / C1) + (1 / C2) + (1 / C3) + ... + (1 / C4))). When capacitors are connected in a series, the total capacitance is decreased due to the equivalent capacitor having the total plate spacing of the individual capacitors.

1. Determine if the circuit contains a series of capacitors

Analyze the circuit, paying particular attention to any groups of capacitors. The capacitors are in a series if there are no existing nodes between the individual capacitors. Putting capacitors in a series is not often done in electronics. However, if there is a need for an increased maximum voltage, then placing capacitors in a series makes sense.

2. Calculate the inverse of each individual capacitor in the series

If the capacitors are 3 uF, 7 uF, 13 uF, and 2 uF, the respective inverses are 0.333, 0.143, 0.077, and 0.5.

3. Add the inverses, and invert the sum

The sum of the inverses of the capacitors is 1.053. Therefore, the capacitance of the capacitors in this series is 0.95 uF.