Parallel and Series Capacitor Calculations Explained for Beginners

Acting like tiny batteries that store electrical energy in an electric field, capacitors are fundamental components in electronics. They’re incorporated into power supplies, timing circuits, and filters in audio equipment, among a broad range of other applications.

If you’re just starting out in electronics – perhaps playing around with a breadboard project, or studying physics at GCSE or A-level – you will often find that in order to achieve a certain desired capacitance value, it is necessary to combine multiple capacitors.

In such situations, you will greatly benefit from understanding what it means when capacitors are linked together in parallel and series configurations, as well as how to perform the associated calculations. So, in this article, we will take a closer look at these vital aspects.

Introducing Capacitance and Capacitors

For readers who may need gaps in their knowledge filled in, let’s go back to the very beginning:

1. Capacitance is the ability of an electrical component, such as a capacitor, to store electric charge, measured as the ratio of the stored charge to the voltage across it (C = Q/V). It’s a measure of the amount of charge (Q) a device can hold for a given potential difference (voltage, or V).
2. A capacitor is a passive electronic component that stores electrical energy in an electric field. In this sense, its behaviour has been likened to that of a tiny and fast-charging (or discharging) battery. It comprises two conductive plates separated by an insulator, the latter called a “dielectric”.

The Essentials of Capacitors in Parallel

Wherever you see a reference to capacitors being connected in parallel, this means they are wired side-by-side in the given circuit. This arrangement effectively increases the total plate area, which in turn, allows the circuit to store more charge.

In a parallel capacitor configuration, the total capacitance is the sum of all the circuit’s individual capacitances. This makes the combination act like one large capacitor.

The formula to remember for figuring out total capacitance across parallel capacitors, then, is: Ctotal = C1 + C2 + C3 + …. So, to give an example, if you were to connect a 10-microfarad (µF) capacitor and a 220µF capacitor in parallel, the total capacitance would be 230µF.

Capacitors are often linked together in parallel in power supplies to smooth out voltage ripples. They are also frequently used in situations where a large value (such as 2,000µF) is required, but only smaller-value capacitors are available.

The Essentials of Capacitors in Series

The connection of capacitors in a series arrangement involves them being placed “end-to-end” in a single path. This configuration causes the voltage to divide across the various capacitors in the chain. However, the charge on each capacitor remains the same.

Arranging capacitors in series causes the total capacitance to decrease. Indeed, in such a network of capacitors, the total capacitance is always less than the smallest individual capacitor in the chain.

To calculate total capacitance for a group of capacitors in series, you will need to use the reciprocal method. So, be sure to take a note of the formula: 1/Ctotal = 1/C1 + 1/C2 + 1/C3 + …. Again, to set out an example: if you have two 10µF capacitors in series, the relevant calculation would be 1/Ctotal = 1/10 + 1/10 = 0.2. Inverting this gives a total of 5µF.

A common motivation for engineers to opt for a series arrangement of capacitors, is so that the total voltage rating can be increased. While the total capacitance drops, the total voltage that such a combination of capacitors can handle is the sum of the individual ratings.

Remember That Online Calculators Are Available to Help!

You can, of course, perform the aforementioned calculations manually. However, to help verify the accuracy of any manual workings-out you do, in addition to boosting efficiency during your projects, it can be useful to have a good capacitor calculation tool bookmarked.

Getting to grips with parallel and series capacitor calculations will greatly help you realise the potential of your electronics projects.