Question: Why do touch pads on computers, and touchscreens on phones only work when our fingers touch them? Why does it not work when we use other objects to make them work?

Kate Husband answered on 24 Jun 2013:

There are a few different ways of doing this but the most common method I think measures the electrical charge at each point on the screen. When you touch the screen with your finger some of the charge dissipates into your finger and that cell on the screen measures than change in charge. This is why other non-conductive things don’t work (and cold fingers!) but why often licking your finger helps if the screen isn’t responding very well as water is a very good conductor and helps to move the charge away.