Capacitors in Parallel

Capacitances in parallel add like resistances in series. The total capacitance is the sum of the individual component values. If two or more capacitors are connected in parallel, and one of the capacitances is far larger than any of the others, the total capacitance can be taken as approximately the value of the biggest one.

Problem 1

Suppose three capacitors are in parallel, having values of C1 = 0.100 μF, C2 = 0.0100 μF, and C3 = 0.001000 μF, as shown in following figure. What is the total capacitance?


Capacitors in parallel.
Add them up: C = 0.100 + 0.0100 + 0.001000 = 0.111000. Because two of the values are given to only three significant figures, the final answer should be stated as C = 0.111 μF.

Problem 2

Suppose two capacitors are in parallel, one with a value of 100 μF and one with a value of 100 pF. What is the net capacitance?
In this case, you can say right away that the net capacitance is 100 μF for practical purposes. The 100-pF capacitor has a value that is only one-millionth of the capacitance of the 100-μF component. The smaller capacitance contributes essentially nothing to the net capacitance of this combination.