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Embedded Systems

Mysterious Tiny Cylinder in Power Cords & Cables

 ferrite bead



In Electronics, sometimes we notice small cylinder in cords and cables, mostly i have noticed it in my laptop’s power adapter and some large USB cables. It is also present in some large range wire with DB9 connetors and in some Printer’s, Monitor cord and Projector’s cables. Today we are going to discuss about that mysterious cylinder.

That tiny cylinder is nothing but a ferrite bead or ferrite choke whatever you say in your local language. A ferrite bead is a passive electric component that suppresses high frequency noise in electronic circuits. It is a specific type of electronic choke. It is also called EMI filters.

ferrite core

Theoretically, this Tiny Cylinder in Power Cords & Cable is ferrite choke or ferrite bead as shown in the images.

Why Ferrite ?

The ferrite choke is an object in the cylindrical shape, which made up of Ferrite material (which is a magnetic material). A typical Ferrite choke (e.g. Solenoid) consists of an insulated wire around a magnetic material. In our case, cable is insulator and ferrite cylinder is magnetic material to make a special kind of lump for the power cable and cords as you can see on cross section cut of this cylinder.

cross section cut of ferrite core

Ferrite Bead (or Ferrite choke) playing a very important role. As we know that, when current passes through the conductors (inside the power cords), it produces EMF (Electromotive Force) or Radio Energy(Electro-magnetic waves). The power cords and cable transfer this energy outside in the form of noise, which disturb and interfere with other electronics devices such as nearby radio sound would be noisy with improper tuning of channel. In addition, some electrical energy is wasted in the form of radiation, which also reduces the supply power to the battery or other connected devices.

Ferrite Bead has the ability to stop and block the emission of radio waves from the power cords and uses electrical energy for charging purpose only without power losses. Due to this important factor, tiny cylinder is implemented in your laptop or mobile charger cords.

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