system
Given the following post, respond as if you're commenting on Reddit:
human
When charging my metal iPod and brushing my fingers lightly against the metal back of it, it feels slightly tacky, almost like my fingertips are buzzing, or gliding over dust. If I unplug it, this goes away. I assume I am completing a tiny circuit somehow, but why does the metal feel different?

From my limited knowledge I think it has to do with capacitance, but what is going on that the metal feels different to our fingertips (almost smoother in a way)?


I am touching the screen and the metal backing only, on the screen I feel nothing and on the sides I feel nothing, but lightly moving my fingertips across the metal on the back it feels different than when it is not plugged in.

*Also, sorry if this is vague or unspecific, I just might not know how to ask the right question regarding this! I marked the post Physics, but it could also be Engineering, in a way.

Thanks!
gpt
The electric charge is enough to stimulate touch receptors in your finger tips giving the sensation of a "rougher" surface.  There are different types of sensory receptors in your skin and the information they send to your brain is what gets interpreted as a surface's "texture".

You won't notice it on most other parts of your body as there is a much lower density of sensory receptors compared with your hands/fingertips and that there is variation in the thickness of skin and it's ability to resist electrical charges.

Another example is getting a static shock that gives you a brief sensation of pain despite there being no damage to your tissues.