CAPACITORS IN SERIES

With capacitors, there is rarely any significant mutual interaction. At very high ac frequencies, however, interelectrode capacitance can sometimes be a problem for engineers. This effect, which shows up as an inherent tiny capacitance between wires that run near and parallel to each other, is almost always undesirable in practical circuits.
Capacitors in series add together like resistors or inductors in parallel. If you connect two capacitors of the same value in series, the result is half the capacitance of either component alone. In general, if there are several capacitors in series, the composite value is less than that of any of the single components. It is important that you always use the same size units when determining the capacitance of any combination. Don’t mix microfarads with picofarads. The answer you get will be in whichever size units you use for the individual components.
Suppose that you have several capacitors with values C₁, C₂, C₃,…, C_n connected in series (Fig. 1). You can find the reciprocal of the total capacitance 1/C using the following formula:

1/C = 1/C₁+1/C₂+1/C₃+... +1/C_n
The total capacitance C is found by taking the reciprocal of the number you get for 1/C.

Fig. 1. Capacitances in series add like resistances or inductances in parallel.