What Is That Small Cylinder On My Laptop Charger Or Computer Cable?

This cylindrical part helps our devices run appropriately.

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A few days ago, I told you about what causes a battery explosion. Today, I’m going to tell you about a small mysterious cylinder found on many cables — particularly the older ones. I noticed a tiny cylinder towards the end of my laptop and monitor cables. This lump is usually found on one side of the cable. So what is it?

It’s a ferrite core that’s used to reduce the electromagnetic interference from the cable, which acts as an ‘unintentional’ antenna, and other devices. The atoms in the core align in such a manner that they cancel the noise. Cables of many modern devices don’t have these lumps as they might’ve incorporated the fixes inside the device itself.

What is this small cylinder on computer cables? What’s its use?

This small cylinder on these cables is a ferrite core, also called a ferrite bead or ferrite choke. It’s simply a hollow cylinder that’s made of ferrite (iron oxide alloyed with other metals), which is a semi-magnetic substance.

Wondering what’s the use? Its purpose is to reduce electromagnetic interference (EMI) and radio frequency interference (RFI).

Such interferences cause our electronic devices to buzz, speakers to chirp, and monitors to flicker when they are too near to cell phones or other devices.

Our cables can act like an ‘unintentional’ antenna that broadcast or pick interference/noise. These cylinders in cables are made in such a way to reduce interference with other electronic devices. In the cylinder, these signals get converted into heat. The ferrite’s atoms align themselves in different directions and block EMI.

Thus, the ferrite core prevents any disturbance and improves the quality of the data stream.

But, why do some cables, e.g., cables of Apple’s products, don’t have these cylinders? In many new products, we don’t see this cylinder as it’s possible that the fixes may be already incorporated internally.


It’s clear that the little cylindrical part aka ferrite bead of your charger has a big purpose. Although we mostly ignore its presence, its effect is always constantly evident as it shields our devices from unnecessary electromagnetic interference which can cause distorted performance. So, the next you notice this charger component, remember well the importance it carries.

I hope you found this explainer on ferrite beads interesting. If you know some other interesting technology facts, do share them with us and let me know if you have other queries or feedback.


1. Are ferrite beads necessary?

Ferrite beads enable a device to avoid unwanted electromagnetic interference from other electronics. So, although not necessary per se, it is a must in today’s world where an average person owns multiple electronic devices.

2. What are the components of a laptop charger?

Components of a laptop charger are a transformer, rectifier, ferrite bead, power plug, charging pin, filters, and regulators.

Adarsh Verma

Adarsh Verma

Fossbytes co-founder and an aspiring entrepreneur who keeps a close eye on open source, tech giants, and security. Get in touch with him by sending an email — [email protected]