Keyboard runs a current through me but not through others

Question

The keyboard is an EagleTec KG010. As you can see in the picture it has a metal top plate.

When I tried it at my place before giving it to my girlfriend nothing of this sort happened. At her place we discovered that when I touch the metal part of it a continuous current flows through me. She had it for weeks now, and it doesn't happen to her. The current is strong enough to cause pain to my finger. She and her mother feel nothing when they touch it. If I try to ground myself with the metal PC case, nothing changes.

For my girlfriend and her mother a voltmeter measures like 0.01 or 0.00 volts between them and the metal part. Between me and the metal part of the keyboard it goes to like 2.5 volts. It doesn't seem to be affected really by socks or flippers or if we're sitting on a chair etc. but to be honest I didn't focus on checking and eliminating such factors.

This not only happens with the keyboard. There's a headphone jack (a metal ring) on her front left speaker. It zaps me as well (it always did but I never gave it much thought until now) when I accidentally touch it. I measured around 2.5 volts between it and me, on my girlfriend, next to nothing. When I touch it however the initial shock stings so much that I can't keep touching it, so it seems it supplies a stronger current than the keyboard.

What could explain the voltage drop happening only relative to me, and the resulting current I feel when touching the keyboard?

Answer 1

(I agree this belongs on electronics.stackexchange.com - not sure why it was moved here)

One of the things which may be at play is the "other part of the circuit". Touching a "live" part won't have any effect if the circuit does not go anywhere (think irds can sitting on wires). It may be that the "path to ground" is through you because of your clothes - particularly the kind of shoes you wear. Another (in my opinion much less likely) possibility is a difference is skin resistance. (Galvanic skin response)

In any event, the difference will be because you are better at completing the electronic circuit then they are.

The worrying thing is that a USB keyboard only requires 5 volts, which can't do what you describe. I would get things checked over by an electrician (or someone with an electrical background - I'd rather not say how here, as this can be dangerous) - it sounds to me like there is a couple of problem - specifically I wonder if the case of the keyboard is somehow connected to neutral rather then ground and why is ground floating so far from neutral?