In some particular days, it seems that my car is somehow at a different potential from the ground. When I get out my car and I wear my sneakers (that I think are better insulators than other kind of shoes) and I touch the metallic gate with my hand or with a key I am holding, I can feel (and see, if it is night) the electric discharge.

I noted that, when it happens, I can feel it not only on my skin but also somewhere inside my knuckle, approximately between finger bones, just before the last phalanx.

My question is: could this be explained from a physical point of view? Could it be that there is a change in the resistance of my finger or something similar to a capacitor in my knuckle?

If this is exclusively related to my sensation of the discharge, then maybe this question is more related to biology. Please excuse me if you consider this question an off-topic.

Thinking again to my question, I experienced the same effect (but through my elbow) when I touched the conducting grid of a mosquito racket (even when it is off, there is a certain voltage, I discovered). Therefore, I don't think it is just a matter of sensations.

This can be related to Factors affecting pain of static electricity shock, even if it is a quite different question.

Edit (23/01/2017): After Squid's comment, I have tried to change clothes, shoes and even to drive another car; in every case, especially in dry and cold days, the electric discharge were produced. Therefore, I think that this static electricity is due to my movements driving, but I still have no idea of why I feel the discharge in my knuckles and not elsewhere.

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    $\begingroup$ The static electricity most likely comes from you rubbing against the car seat and your clothes and the fabric of the seat being such that a transfer of charge takes place. The surface of the car is most likely at the same potential as the ground. $\endgroup$ – Squid Jan 7 '17 at 19:26
  • $\begingroup$ @Squid I'll try to change material of my clothes and see if this repeats, or try to touch the surface of the car before I touch the gate. Thank you for your suggestion! (do you have any guess about my problem in understanding why I feel the discharge where I actually feel it?) $\endgroup$ – JackI Jan 7 '17 at 20:18
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    $\begingroup$ I've seen conflicting arguments regarding whether the pain from static shocks is due to heat production or general neural electrical confusion in response to the current so I don't really have a solid idea. I lean towards it being a slightly more sensitive neuron associated with that sensation than there being some different process taking place in the joint, but that's wild speculation. $\endgroup$ – Squid Jan 7 '17 at 22:12
  • $\begingroup$ @Squid maybe this could be an idea for a quite interesting question! $\endgroup$ – JackI Jan 7 '17 at 22:18
  • $\begingroup$ The mosquito racket retains the potential in the grid even after you turn it off until it is touched at least once or enough time has passed. $\endgroup$ – Yashas Feb 7 '17 at 7:24

The elbow ("funny bone") is particularly sensitive to knocks because the ulnar nerve is close to the skin and unprotected at this point. The sensation when it is knocked is often described as being like an electric shock.

Part of the explanation may be that the nerves are more exposed to the electrical discharge at the elbow and knuckle, so you are more aware of it here. But also, since the purpose of nerves is to transmit electrical signals through the body, the nerves and also the fluid in joints offer a path of low resistance.

See : https://www.quora.com/Why-do-we-feel-a-shock-like-an-electric-current-when-our-elbow-is-hurt-on-a-specific-point.

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  • $\begingroup$ Ok, this may be suitable for the sensation in the elbow, even if I don't understand the relationship between closeness of the nerve to the skin and sensitivity to electric discharge through your arm. But how does this applies to my fingers? I have never heard that in knuckles there are particularly exposed nerves, also because you use this part of your body for knocking. $\endgroup$ – JackI Jan 8 '17 at 6:10

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