Whether you’re a hobbyist fiddling with a Raspberry Pi or a professional engineer designing a filter for a solar inverter, you will benefit greatly from having a broad-based and in-depth knowledge and understanding of capacitance.
Certainly, a capacitor is a component of fundamental importance across all manner of electrical and engineering projects. It is vital for storing energy and managing current flow in everything from simple household gadgets to complex industrial systems.
Something else that anyone working with electronics needs to know about, is the distinction between parallel and series capacitance, and the principles underpinning them.
This article, then, will take a closer look at this topic. Along the way, we will provide simple formulas illustrated by practical, “real-world” examples of when both series and parallel capacitance come into play.
A Quick Introduction to Capacitance
Measured in farads (F) – a unit named after the English chemist and physicist Michael Faraday (1791-1867) – capacitance is the ability of an object to store an electrical charge. This is quantified by the ratio of the charge stored to the change in electric potential (voltage) across it.
A capacitor, then, is an electronic component that stores electrical energy in an electric field. It achieves this by accumulating opposite charges on two conductive plates, with an insulating material – known as a “dielectric” – separating them.
In many circuits, smaller units than farads are used, such as microfarads (µF), nanofarads (nF), or picofarads (pF).
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Capacitors In Parallel: The Concept
When you see a reference to capacitors being “in parallel” in a circuit, this means they are connected side by side. This arrangement involves one plate of each capacitor being connected to one side of the power source, and the other plate to the other side.
Capacitors being in parallel means their total capacitance (Ctotal) will be the sum of the individual capacitances. This is because linking these components in parallel effectively increases the total surface area of the conductive plates.
Capacitors In Parallel: The Calculation
The relevant formula, then, is: Ctotal = C1 + C2 + C3 + … + Cn.
To apply a real-world example, let’s imagine that you’re upgrading an audio hi-fi system. Your speakers include a crossover network with capacitors to filter frequencies. You decide to boost capacitance in the high-frequency section, by adding a 10 µF capacitor in parallel with an existing 22 µF capacitor.
You can therefore figure out the new total capacitance with the formula: Ctotal = 10 µF + 22 µF = 32 µF.
As a consequence of this increased total capacitance, the crossover can now handle a wider range of frequencies, which could translate to improved sound quality.
Capacitors In Series: The Concept
A series configuration, on the other hand, entails capacitors being linked end-to-end in a single line. This means the same charge flows through each of them.
Unlike the situation with parallel connections, if capacitors are arranged in series, the total capacitance will always be less than the value of the smallest individual capacitor.
This decrease in the total capacitance occurs because the effective distance between the plates increases, thereby lowering the ability to store charge.
Capacitors In Series: The Calculation
You can figure out the total capacitance of capacitors in series, then, by applying this formula: 1 / Ctotal = 1 / C1 + 1 / C2 + … + 1 /Cn. If there are just two capacitors involved, this formula can be used: Ctotal = (C1 x C2) / (C1 + C2).
For a real-world example, let’s picture a situation where you’re repairing a power supply for a vintage BBC Micro computer. The circuit needs a particular capacitance to smooth out voltage ripples. You ultimately decide to have two capacitors, 100 µF and 150 µF, connected in series due to space constraints.
The calculation would therefore be: Ctotal = (100 x 150 µF) / (100 + 150 µF) = 60 µF. This result is produced because the calculations in brackets give readings of 15,000 µF and 250 µF respectively, and when you divide 15,000 by 250, you get 60.
A total capacitance of 60 µF may be enough for the power supply’s smoothing needs. However, you will need to check the requirements of the specific circuit.
But There’s Another Way to Carry Out Parallel and Series Capacitance Calculations
We are, of course, referring to the tools you can find online – or even incorporated into broader circuit design software packages – that make it quick and easy to calculate parallel and series capacitance.
Using such a calculator can be as simple as specifying whether you need to figure out the capacitance for a series or parallel circuit, before entering the relevant capacitor values, and hitting the “Calculate” button.
A series and parallel capacitance calculator can be greatly useful for verifying the accuracy of the results you gain from manual calculations. This, in turn, can enable you to proceed with confidence when handling capacitors in almost any given project.
