Kelvin Water Dropper with Electroscope: Thunderstorm Warning
Channel: Reinhard Schumacher
Date: 07/12/2011

Kevin Water Dropper or Lord Kelvin's Thunderstorm is an amazing device that creates sparks from water falling freely through an open can into a bucket.  It works on the basis of electrostatic induction.  This version has an electroscope attached to visualize the build-up of charge.