Admittedly I'm clueless when it comes to electrical engineering. I felt compelled to add a ferrite bead/choke/clamp to my computer's power cord since it was missing one. Would it be helpful? What kind should I get, or are most sold generally the same? Does the wire need to wrap around the ferrite bead, or can I just clamp on the bead and call it a day? Thanks a bunch!

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    \$\begingroup\$ A better question would be, "why do some computer cables need ferrite beads?". For the answer, see below from Olin. \$\endgroup\$ Dec 12, 2017 at 17:29

2 Answers 2


A ferrite bead around a cable adds common mode inductance to the cable. The purpose is to increase the impedance of the cable at high frequencies. With higher impedance, less power can be radiated or conducted from the cable.

Whether your cable needs a ferrite around it depends on whether you need to reduce the conducted or radiated emissions at high frequencies. If it is for personal use, then there is little reason to bother.

If you are trying to sell a product, then you have to make sure it conforms to the emissions standards in whatever jurisdiction you offer it for sale in. In the US, these standards are defined in part 15 of the FCC rules. In Europe, you generally need to meet CE specifications.


If you use a handheld ham radio close to your computer, a ferrite bread helps reduce interference from the electromagnetic energy radiated from the power cord.

I just got my ham radio license and when I use my hand held radio at the desk in my home office that has two computers, four monitors, and a 43 in TV on it, there is a noticeable hum when I am listening to the radio. People at the other end don't hear it, but it certainly makes it harder for me to hear them.

I reported the hum to another amateur radio operator yesterday, who explained I need to add ferrite chokes to reduce the RF (Radio Frequency) interference.

I'm now trying to figure out how to get the right size ferrite chokes for all the power cords in the room.

There may be other types of sensitive electronic equipment that are also affected by that electromagnetic energy.

If you have electronics affected this way, adding a ferrite bead to the power cords in the area (get the right size for each power cord and simply snap it on to the cord) should help.

Most people won't need this.


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