What The Strange Knob On Your Computer Cable Is For

Anyone who works or plays on a laptop has surely noticed this funny round and knobby thing on their charging cable. Every laptop charger has this so-called ferrite core, but very few people know what this thing is good for. We'll explain it to you.

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

Many people out there probably work with a laptop on a daily basis. Maybe you also use your laptop for gaming. But just like me, you've probably never taken a closer look at your laptop charger, have you? If you have, you might have noticed that strange knobby thing, the weird little cylinder that goes around the cable. But do you even know what it is? Most people probably don't even care at first, as long as the laptop does what it's supposed to and the charging cable charges as usual.

But since you clicked on this article, you're most likely asking yourself this very question right now: "What is this weird thing and what does it do anyway?" Don't worry, we'll explain, that's what we're here for.

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. 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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