This Is What Inside The Tiny Little Cylinder Of Your Laptop Charger

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Have you ever thought why there exists a tiny little cylinder on your laptop charger? Today we are going to reveal the secret behind it.

These cylindrical shaped bumps are not only found in laptop chargers but also in many other power cords, such as: mouse, keyboard, monitor cables, printer cables etc. These bumps are theoretically called as ferrite beads or ferrite chokes. Here is how they look like:

What Is Inside The Tiny Little Cylinder Of Your Laptop Charger 2

What would happen if the charging cable was not designed to have the little cylinder? We all know that an electrical current passes through a charging cable in order to power up any device battery. Due to this electric current in the cable, it creates radio energy within itself and emits it in the form of waves outside the cable.

This phenomenon is similar to how an antenna works i.e. converting an electrical power into radio energy and vice versa. Just like an antenna, this cable transmits and receives signals to or from surrounding gadgets with same capability. Due to this, the electric power gets used in unnecessary function and hinders charging the actual device. In addition, these signals can interfere with other electronic devices resulting in noisy signals such as a nearby radio gives distorted voice or does not tune up to a channel.

What Is Inside The Tiny Little Cylinder Of Your Laptop Charger 3This is why a ferrite bead is inserted to a charger. It has the capability of blocking the emission of radio waves from the cable so that it uses electrical power for charging purpose only. A typical ferrite bead is formed through an insulated wire wrapped around a magnetic material just like it is shown in the picture below. In our case, the charging cable is the insulated wire and the ferrite cylinder is the magnetic material which together form a special kind of lump for the charger.

ferrite bead inside

This proves the fact that in science little details matter the most or otherwise it would have been a chaos.

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10 Comments to This Is What Inside The Tiny Little Cylinder Of Your Laptop Charger

  1. As written ferrite bead cylinder act as a absorber of radio energy (waves) generated by copper cables, could you please tell us how this will going to happen inside the inductor in detail?

    • A ferrite bead is just a cylinder made of ferrite snapped around the charging cable. The reason it is able to block the radio frequency is due to ferrite material.
      Ferrite is composed of different metal oxides (Iron, Manganese, Manganese Zinc, nickel zinc etc.) which makes the material highly permeable. Now, as you may know, permeability means that how much a material can support the formation of magnetic field within it. When materials have high permeability, they get the ability to absorb the magnetic energy.
      That is why when ferrite bead surrounds the cable (a conductor), they act as frequency dependent resistors, allow DC to pass, absorb radio energy and release it in the form of heat.
      You can read in more detail here.

  2. The ferrite bead is actually used to stop fluctuations and ripples in the voltage being delivered to the laptop and not to prevent emissions and leakge of radio waves. Get it correct.
    Source: I design electronics

    • I am going to disagree with you AND the article.

      The ferrite is used to stop RF from being fed back into the power lines and transmitted from them. The switching voltage converters / regulators in devices operate at RF frequencies. Their operation feeds RF back into the power input and into the mains.

      The use on a USB cable is similar. In this case the USB cables inside the computer chassis pick up RF from the motherboard and other devices. The USB wires provide a path to outside of the chassis. The chassis otherwise blocks these signals.

      They also operate in the reverse. External RF cannot get into the chassis and disrupt the computer.

      As a ham radio operator I am familiar with this since my transmitter can cause disruption to TV and other devices. Look at the labels on your equipment and you will see one that says something like “…must accept interference…”. This is on there to protect hams like myself and other licensed radio emitters because it is your device that was not built properly to reject the RF. That saved you and the manufacturer some money.

  3. Michael Hardy

    “This phenomena is similar to how an antenna works”

    Please: Write “This phenomenon is” or “These phenomena are”.

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