Let's say I touched the live wire of a power socket in my apartment that is located at the fourth floor of an apartment building. The current needs to flow through my body to ground in order for me to get shocked. According to some sources the human body has a resistance that is quite dependent on several conditions, and can be as low as a couple of thousand ohms, so touching the high voltage with feet grounded definitely is dangerous. But how is my body grounded inside my apartment? There is a thick layer of wood and concrete under my feet, and several other apartments below me. Even if my body resistance would be low, wouldn't there be still very high resistance between my feet and the ground?

I read this question but I don't think it really answered the question: Why do you get shocked touching a live wire?

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    \$\begingroup\$ "Ground" does not mean what you think it means. It is just a reference that in electrical systems is generally connected to a nearby earth potential. But there is plenty of "ground" around you. All of the wiring, all of your appliances, much of the water pipes and A/C conduits. All of this provides a capacitive path from your body for current return. This, however, does not fully answer the question. \$\endgroup\$ Jan 22, 2019 at 23:01

1 Answer 1


Our body is both a variable skin resistance and a lossy dielectric capacitor depending on the surface area. If perfectly insulated on clean Teflon plastic or mica sheets you would not feel anything.

But with humidity, there is stray capacitance in the air and sweaty socks on humid floors may conduct even more. ( Moisture has 80x the relative dielectric constant of air meaning lower impedance at some frequency.)

Even concrete can contain some moisture but is definitely drier than on soil. Most of the capacitance is from surface moisture and RH in the air.

Obviously touching a metal earth bonded appliance or plumbing provides direct contact to earth bonded wiring. The 2 pronged metal skin appliances ( like toasters) must have "Double insulated" plastic or mica materials for redundancy. However, water immersion cleaning can bypass this if any residue is left behind. ( so warnings exist)

So what floor you live on has nothing to do with the Earth ground resistance which often defined as < 100 Ohm depending on what it is protecting.

Nor does the risk of shock or the equivalent impedance having anything to do with what floor you live on.

A fingertip ( often rated at 100pF for ESD) might have a dry resistance from >10M to <10k with an arc from ionization of the sweat gland moisture on the skin.

0.25 mA ~ 0.5mA is what North America uses for GFCI ground fault interrupters which are also the limit for insulation leakage current from line filters to ground in 3 pronged plugs.

While ( I recall) EU standards for GFCI use 20mA for GFCI's which prevent false tripping and might hurt but should not kill you. The IEC standards group for EU are reviewing this standard, I believe, for risks vs nuisance trips and possible changes.


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