cauliflowell

i was practicing on my electric guitar and i wanted to find something on my phone. so while resting my arm on the strings of the guitar i placed my thumb on the home button (i have an iphone 7, which uses the fingerprint sensor home button which is a sapphire crystal and uses a complimentary metal oxide semiconductor capacitive touch sensor to detect the fingerprints electrical charge or something right? ) and it gave my arm a very small electric shock! the amp also gives feedback whenever i place my thumb on the home button as well however, it seems this only happens when my phone is charging! i think i might have some idea of what’s going on here... but i’m not too confident so if anyone could suggest why this is happening that would be great! thank you