I have a bit of trouble understanding the electrical laws which apply when I touch a capacitive touchscreen with my finger.
Apparently, there is an electric current running through electrodes below the glass screen. When my finger is close to the glass, it modifies the electrical field below the glass and the phone can detect the exact position of the modification.
First, why do my fingers modify the electrical field? Is it because my electrical potential will always be different than the one on the phone? If so, why?
Does my finger really pick up charges from the phone? If so, there should be a closed-circuit for the current to flow. But as I understand it, the capacitor is made of : my body (1st terminal), the insulator (the glass), and the electrodes below the screen (2nd terminal). As the first terminal is connected the earth, a current can flow. But what if I do not touch earth?
Finally, can a capacitive stylus work without being held by a human hand?