...Aka the Kelvin hydroelectric generator, the Kelvin electrostatic generator, or Lord Kelvin's thunderstorm.
Let's start with 2 metal cups, one above the other, in such a way that the top cup can pour its contents below it into the bottom cup. At this point, they are both uncharged. If we could magically make the top cup negatively charged, would the bottom cup become positively charged per the electrostatic induction effect? Or would something else happen? (Or nothing happens to the bottom cup?)
Secondly, if we pour the water from the negatively charged top cup into the bottom cup in such a way that a solid stream is prevented from connecting the two cups electrically, would the top cup and bottom cup switch electrical charge signs? I mean, would the top cup become positively charged and the bottom cup negatively charged?