system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the touchscreen works with the negative pole of a battery?
gpt
The actual answer is that phone screens sense changes in capacitance. The positive terminal of a battery goes right to the inside of the battery - which isn't a lot of material and has low capacitance.

The negative terminal, however, is actually bigger than you think - the entire case of the battery often functions as a negative terminal. So when you grab the battery, you are touching the negative terminal. Basically the negative terminal completes the circuit between your hand and the phone screen, so it works.