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When lightning strikes or the earth wire (from the wall outlet) suddenly gets charged negatively for whatever reason, then, in theory, can it cause ESD-damage to a PC?

Because the grounding wire (inside the ATX power cable) connects earth directly to the motherboard's ground-plane.

If earth is more negative, the ground-plane accepts electrons from earth. Can this charge move too fast (if the potenial is large enough) and cause ESD-damage?

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  • \$\begingroup\$ See also electronics.stackexchange.com/questions/222502/… \$\endgroup\$ – pjc50 Feb 25 '17 at 20:15
  • \$\begingroup\$ (also, esd damage is not the mere presence of charge, it has to flow somewhere in a circuit) \$\endgroup\$ – pjc50 Feb 25 '17 at 20:35
  • \$\begingroup\$ @pjc50 Thanks. Yes, flow of charge. But when electrons enter the earth when lightning strikes, that's a flow of charge. These electrons can flow further into the motherboard, right? (Until everything is at the same potential.) \$\endgroup\$ – Marty Feb 26 '17 at 10:54
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PC components are protected in a Faraday cage.

A sudden charge applied to a metal-cased personal computer will quickly come to reside on the outer surface of the metal case; this is because charge repels. For very short times, a narrow wire (grounding wire inside the case) may be a flow constriction, but most PC internal construction includes a grounded metal case around the power supply (which is the terminus of the incoming ground wire), so the likely place to look for any transient damage is not the logic board, but the power supply.

A damaged power supply might overstress any and all electronic parts to which it is connected. Lightning, nearby, might generate enough radio frequency energy to put damaging currents into peripheral (USB, video, etc.) wires, which is why they are equipped with grounded shields.

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  • \$\begingroup\$ But that Faraday cage, the ATX case, is connected directly to the ground-plane of the motherboard... Earth is connected directly to the ground-plane of the motherboard, via the case and the PSU. \$\endgroup\$ – Marty Feb 28 '17 at 0:09
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    \$\begingroup\$ The importance of a Faraday cage is that there are no electric fields inside; the 'connected directly' motherboard IS inside the case, so the wire carries no current, the board holds no net charge. \$\endgroup\$ – Whit3rd Feb 28 '17 at 3:50
  • \$\begingroup\$ Thanks! Are you sure? Because 'a wire into a Faraday cage' means: a leak. Besides that: lightning doesn't (need to) hit the cage, it is a discharge to earth. \$\endgroup\$ – Marty Feb 28 '17 at 10:17
  • \$\begingroup\$ @Marty: yes, I'm sure a Faraday cage protects against lightning. One such is depicted here, doing almost exactly that: <mos.org/live-presentations/lightning>. The 'leak' is of no importance if there's no pressure (i.e. no field inside the Faraday cage). \$\endgroup\$ – Whit3rd Feb 28 '17 at 10:56

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