[sitharus]

They can’t, it’s caused by the capacitors required to suppress electromagnetic interference caused by the switch-mode power supply. These allow a very very tiny amount of current to leak through from the mains side, which is then capacitively coupled to the metal case (IIRC Apple do not connect the case to power negative) reducing it further, but it’s enough for humans to sense it.

It can be avoided by using a grounded power supply, but because there are large countries that have ungrounded outlets in common use the most designs are ungrounded.

[ranger207]

Why do only Macbooks suffer from this problem? When I had a work-issued Macbook I charged it and my personal Framework off the same USB-C charger and I only every felt the leaking current from the Macbook

[numpad0]

Only Apple is insane enough to make actual laptop chassis with unpainted anodized aluminum. Others either do it in plastics and/or painted metal. And paints are kind of liquid plastics.

[RealityVoid]

It's not only mac's suffering from this problem. My old dell latitude with magnesium case had the same thing. I didn't fully understand why and some people thought I was mad for feeling it but it was there.

[normie3000]

Additional question: why do only some people notice?

[sitharus]

It’ll depend on how well grounded you are compared to how well grounded the laptop is, where it’s touching your body, and your sensitivity to electricity which varies.

[wazoox]

My aluminium body Lenovo IdeaPad has exactly the same problem.

[black_puppydog]

Thank you for explaining this! I've been feeling this on my girlfriend's macbook for years and I've always wondered what the hell that was. :D

[robotbikes]

I once had an HP with an aluminum case and it had a grounded power supply but if you plugged it in without grounding his an adapter (sometimes you gotta do what you gotta do). You could feel it straight up vibrate while conducting current if you rubbed your hand over it. Not enough to shock me but it felt like kind of a shoddy design and leaked a lot more current than I've felt on a MacBook.

[ebbi]

Is that what it is! On my pre-unibody MBP I used to run my finger across the body sometimes and it had this weird wavy feeling (honestly can't describe it well). I thought it was just a quirk of the aluminium itself!

[Jolter]

Definitely been a long standing issue on many laptops with exposed metal parts. Late 90’s, if I used my brother’s Compaq while putting my feet up on the radiator, the metal speaker grills would give me mild shocks.