Why is this ESD happening? Touching macbooks produces electric discharges

rodion15

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I'm not really sure this issue I'll explain here is static electricity related:

When we touch macbooks we sometimes feel an acute electric discharge.
I measured the conductivity of the macbook outer cases with an ohmmeter and found them non-conductive (2009 to 2015 macbook models). My only explanation is that the macbooks have some outer layer of non-conductive material on the cases, and perhaps when these electric shocks happen you maybe brushing (typically with our forearms) on some of the corners where there may be a non insulated and therefore conductive spot on the macbook case. Looks like the person touching the macbook has a big static electricity buildup on their body (we have fitted carpets, which I understand create a lot of static), and then touching the macbook discharges the static to ground through the power adapter, which is also grounded.

I would really like to know why this is happening.

 

Steven Jiang

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Normally, "static build up" is just another way of saying charges being built up in a body but cannot move to a lower charge material. When we have a charge build up, free Electrons gather in our body which makes our body gain charge. When we touch electronics(which are good electricity conductors) or any conductive material that have lower charge than us, the electrons in our body will move into the material as we touch it, making us feel a "static discharge"(a zap). The reverse is also true, if the material is charged and we are of less charge, the electrons in the electronic move to our body and we also feel a "static discharge".
I would say that your reason is plausible, as i experience the same with my macbook only on the corners, and it is avoided when i plug it into a wall plug with a ground(I used to have it plug into a extension plug and it might not have a ground cable installed). It doesn't happen on battery though.
 

rodion15

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Thanks for your answer. Well, yesterday I pinched the corners of the macbook with a multimeter (one of the probes touching the ground on the socket or close to the other probe on a macbook corner) and I couldn't measure any "nude" conducting spot on the macbook. We're using three-prong sockets and I checked it's grounded using the the multimeter. Anyway, I think an ESD would be stronger of you touched a grounded conductor than if you touched a non-grounded one, since the potential difference would be higher Yourself-to-grounded-conductor than Yourself-to-conductor alone.
 

Steven Jiang

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yep.
 
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