I bet no one ever thought of this until now.
So you have been using your laptops for years
And it is mostly plugged to an electric socket
Now people are wondering, what small cylinder?
Yes that small Cylinder
The cylinder is known as Ferrite Bead.A ferrite bead, or ferrite choke, is a simple hollow cylinder or bead that is made of ferrite material and that is used in order to suppress or filter the amount of high frequency electromagnetic interference (EMI) noise found in electronic circuits.
It isolates the laptop from the electro-magnetic noise that occurs from the waves picked up by the cable, or from the noise in AC-DC converter.
It is a kind of electronic choke
It dissipates high-frequency currents in a ferrite ceramic, and helps make the most powerful noise suppression device! It is called a core, block, or EMI ring.
So, that is what it is all about.
Do share this significant piece of knowledge with your friends. Of course, after asking them about it, and projecting yourself as the smarter one!