Tech: What The Strange Knob On Your Computer Cable Is For

For anyone who works or plays on a laptop, you've likely witnessed the peculiar round and knobby object on your charging cable. Every laptop charger includes one of this so-called ferrite cores, yet its purpose remains largely unknown to many. Let us explain its function to you.

Laptop ferrite core
We'll explain what that strange cylinder on your charging cable is. | © EarlyGame

Many people use a laptop daily, whether for work or gaming. However, like most, you probably haven't paid much attention to your laptop charger. Have you ever noticed that odd, knobby cylinder on the cable? Do you know what it is? Most people don't think much about it as long as their laptop works and charges properly.

But since you're reading this article, you're probably curious: "What is that weird thing and what does it do?" Don't worry, we're here to explain it to you.

This Is Why You Need A Ferrite Core

As you've just read, the strange cylinder on your laptop charging cable is a ferrite core, also called a ferrite bead. In short, this ferrite core is a filter that ensures that other electronic devices in the vicinity of your laptop are not disturbed by electromagnetic interferences. But of course, you need some more input here. You're probably wondering now why your laptop should interfere with other devices at all, and how a weird plastic cylinder can prevent that. So here's the more detailed explanation.

Electronic devices, such as your laptop, generate electromagnetic waves that are transmitted by the laptop charging cable and emitted into the environment. These waves can now lead to interference with other electronic devices.

Ferrite Core Clamp On
This is what the ferrite core looks like inside the knob. | © Wikimedia Commons

A common example here would be your Wi-Fi. If your Wi-Fi is transmitting on the same wavelength, you might have problems with the connection. The electromagnetic waves can also cause monitors to flicker or speakers to chirp. These are all issues that we don't want to have, of course.

To prevent all this from happening in the first place, laptop charging cables have the ferrite core. This "filter" is placed on the cable, just behind the plug that goes into your laptop. Inside the plastic cylinder is, as you might have guessed, a ferrite core through which the charging cable passes. Ferrite is a material that is not electrically conductive at all, or at least barely, and thus absorbs the electromagnetic waves that are passed through the charging cable. As soon as the charging cable passes through the strange cylinder and thus the ferrite core, all electromagnetic waves are absorbed and therefore can't cause any interferences with other electronic devices anymore.

So now you know what this funny round thing on your laptop charging cable is and that it actually has a purpose. If your charging cable doesn't have a ferrite core, like on a Mac for example, you don't have to worry. Many newer electronic devices already have these ferrite cores integrated into the device and thus don't need to attach it to the charging cable.

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Lukas Ballat

Lukas has been passionate about shooters his whole life and at EarlyGame he teaches you everything about CoD, while also taking care of campaigns and partner projects. He also plays Souls-likes and doesn't shy away from the Diablo-grind either....