Why does the edge of the phone seem to conduct electricity?


I’m not sure if this is intended behaviour or a problem with my device specifically, but it seems to me like the metal edge of the core part of the phone (the strip that runs around the outside, in which the buttons, the usb port, etc are housed) conducts while the phone is charging.

I discovered this because I often work with my phone and my laptop both plugged in at the same time and with earphones plugged into the laptop.

When I touch the metal outside of the phone (not the screen or back, just the metal strip around the edges) I can hear a buzzing in the earphones

I think there’s some kind of circuit forming from mains → my fp4 → through my body → my earphones → my laptop → back to mains or something - I know that sounds insane but I can’t think of another reason this would be happening. Disconnecting the charging cables from either the phone or the laptop and then completing the “circuit” does not cause the buzzing - it only happens when both are plugged in??

I don’t really know what my question is here but like… can anyone else reproduce this? Does this only happen on my hardware? Could it be indicative of problems with my phone?

I’ve had some other issues (like the ghost inputs described in Ghost inputs on FP4 and audio issues), wondering if this could be related…

Anyway, thanks for reading/any help you can provide on this very weird problem!!

1 Like

I don’t hear a sound in my (bluetooth) headphones, but I have noticed a similar effect as well.

For me it only happens when the phone is charging and I don’t hold it in my hand. If I slide along the left side of the frame, specifically those two short antenna sections, I can feel a tingling electric current.

I’ve had that for a while and I can reproduce it with a second FP4. Once charging stops, the effect goes away, picking the phone up will also stop it.

Oh, and welcome to the community :wave:



Maybe you can provide some more info on the situation how devices are interconnected.

“both plugged in at the same time”

Where into? Wall power socket, multi-extension socket.
What kind of charging device laptop USB-C or barrel port?
FP4 charger from Fairphone shop or different type?
Which FP4 USB-C cable, Fairphone shop or different type?
Any other devices also plugged into the same wall power outlet (maybe dual or triple port wall outlet)?
Any other devices also plugged into the same multi-extension socket (docking station, external display, hi-fi…)?

Maybe try a different setup to verify. Different FP4 USB-C charger, different USB-C cable, different pluggable earphones.
So it only occurs when mobile and laptop are charging/connected to a power socket using their USB-C
or maybe barrel port connection?

Strip down the entire setup. Use original parts where possible. Connect your laptop with its original charger in one wall power socket (no multi-extension, no docking station, usb hub, external display or else extension).
Connect your FP4 charger into the neighbor wall power socket if available or use a (different) multi-extension (preferable without power switch if you have one) with just these two devices connected.

Does the effect still happen?

1 Like

It’s not a conductive issue but an induction one, although holding the metal frame massively increases the induction.

I reside off grid and the nearest mains electricity is a neighbour 100m away. While I inhabited an aluminium caravan I would get a 50Hz hum when I touch some audio equipment.

The 50Hz travels through just about anything that isn’t an insulator. The earth carries signals miles, hundreds of miles etc. and the metal housing acts as an antenna, so does the body.

So if your body pickes up the 50Hz it is inducted into the metal frame and from there into the phone.

A type of unwanted induction simialrly induced as would be by wireless charging.

By the way as the edge is metal it will conduct electricty.


In my opinion and experience feeling the electric charge is quite a common phenomenon with ungrounded small electronic devices when connected to a mains charger. Laptops with metal casing are a typical example.

Of course this is only observed in devices that have a metal housing.

As for the buzzing, you’ll often hear that if you touch an audio jack connected to the AUX input of an old-fashioned hi-fi amplifier or electronic musical instruments. If your phone and laptop are connected to the same mains supply socket I wouldn’t be at all surprised to observe the same phenomenon. If you search around you’ll find quite a lot on this EMF effect. See for example

Electromagnetic interference

Mains hum

You can probably avoid the hum by using a separate mains ring to power the two devices, plugging one at a time, or charging the phone from a power bank. You might also try charging the phone from a USB port on the laptop, since in that case only one power supply is concerned. However you may observe electric field effects when touching the phone since your body acts as an antenna.

I was about to say that amoun will have a contribution to make on this, but I see he just has :slightly_smiling_face:


You probably find if you touch the phone body with one finger (and nothing else) while charging, and move the finger around, you will feel a strange feeling. I don’t know about audio issues but that feeling is not unusual for metal-bodied phones; it is caused by coupling across a filter capacitor in the USB charger. Incidentally this is why it is a BAD idea to use cheap dodgy chargers of shady origin (e.g. buying cheap charger off eBay or AliExpress) - if that capacitor (or the transformer in the charger) fails you can end up with mains going to the output which, as you can see, is connected to the metal case of the device. There are a lot of dangerous cheap chargers around that use underrated and unsafe component choices including that specific capacitor which is supposed to be a proper safety class.


I agree with joshj. I made a guitar amplifier once and used an old charger as the power supply. I found that when I picked up the guitar it tingled as I played. I thought I was imagining it but in the end I put a voltmeter on some bits and measured 117V! There must have been a tiny current as it hadn’t tripped the RCD and it’s so long ago I can’t remember the full details but I just changed the power supply and it was no longer there. Please be careful!

Worth noting the weird vibrating feeling in itself isn’t an indication of a problem, it just means the charger is of a particular design. I get it with my FP4 using Fairphone’s own charger. But it is a reminder that you really don’t want to use dodgy chargers because all that’s between you and high voltage is that capacitor, and in some of the dodgy ones just some lacquer on some wires in a badly constructed transformer.

Weird vibrating feeling or not, charger safety is really important. You don’t want your charger cable or your phone itself becoming live!

@aylicarper @joshj and others

The OP mentions a buzzing in the headphones not a tingling in the fingers, though such as you mention does occur :zap:

EMI would be radio frequency, way above audible frequencies.

Mains hum would be a continuous noise in the frequency of the AC mains and its harmonics.

My best guess is a ground loop.


EMI occurs at all frequencies 0+ to infinity.

Radio frequencies are a small band of EMF (EFI interferers)

Mains frequencies of 50 or 60(Hz) induce potential to other conductive material especially sensitive amplifiers as are used in phones.

Whereas a ground loop may trap and amplify such and the 50Hz AC produces a 50Hz EMF which will induce EMI at harmonics.

1 Like

You’re more an expert than I am. ‘Sorry!’ to anybody I have confused.


Hey all, thank you for the responses - I’m using original manufacturer chargers for both phone and laptop.

Sounds like it’s probably not a problem then, and the solution to the audio issue is “just don’t touch the phone while listening to music on the laptop and both are plugged in”?

Or is there a safety issue with one/both of the chargers? Thanks!

I doubt there’s a safety issue as you would likely feel a tingling if the metal edge was connected to a voltage.

Tingling does take a few volts 20 to 30 maybe and wet hands. if you can find a voltmeter try testing the voltage (potential difference0 between the case edge when plugged in and the ground, maybe a metal pipe feeding water or if you have a three pin mains socket that ‘should’ work.

That’s because bluetooth headphones are wireless. First comment clearly said “headphones plugged in”.

I’m not the exepert, but as soon as I read the main comment I understood. Although I have to admit I also quickly thought of the feeling of electrical issues, like many more before me. For example, I have a Samsung all-in-on pc and when it’s on, I can feel such a tingling on the metal edge too. And that does NOT feel safe to me. It’s also the same feeling on one of those fancy lamps where you briefly touch the metal base and the light goes through three or four levels: off, low, high light.

1 Like

I mean, yeah, obviously Bluetooth is wireless, that’s why I added that information in parenthesis :nerd_face:

My main point was about the electrostatic charge I can feel.

I use a non-official high-quality charger. I took a voltmeter and measured the voltage between my wall socket’s ground pin and the phone edge (in multiple places) while the phone is charging. There’s just nothing there. 0.1 mV, which is probably just the error of the measurement.

1 Like

Did you measure AC or DC?

I measured DC.
. . .

But the problem comes from AC :wink:.

1 Like