A number of times (over many years) I've accidentally touched a live AC mains wire (120V, 60Hz) while working on home wiring. The feeling is always similar: uncomfortable tingling feeling at the point of contact (generally the tip of my finger). In all cases, I most certainly have not had "good" contact with ground (for example, when it occurred today, I was standing on a plastic stool, with rubber soled shoes).
My question is: why do I feel a shock?
- My resistance to ground is too high to have any non-negligible current.
- My capacitance to ground seems not high enough to have a noticeable shock (see below).
I see some resources online suggesting a capacitance to ground of a few 100 pF. If true, then (assuming 100 pF capacitance):
Z = 1/(2*Pi*f*C) =~ 26 MOhms I = V/Z = 120V / 26 MOhms =~ 5 uA
The threshold of sensation is generally specified to be around 1mA (somewhat less at 60Hz). So, if my body capacitance is correct, then I'd expect to feel a sensation only at voltage 100 times higher (10kV). Of course, my body capacitance could be wrong. Is it, or is there a different effect going on?
Question part 2: Why is the sensation only in my fingertip?