The Kelvin Water Dropper, also known as Kelvin's thunderstorm, is an electrostatic generator that converts falling water into static electricity. It was invented in 1867 by the Scottish scientist William Thomson, later known as Lord Kelvin. The device uses the principles of electrostatic induction to generate high voltages from the gravitational potential energy of falling water droplets.
In the Kelvin Water Dropper, water flows through two separate nozzles, falling into two containers that are connected to metal electrodes. Initially, a small natural imbalance in charge causes one stream to become slightly more negatively charged, and the other slightly more positively charged. As the droplets fall, they induce opposite charges in the containers below them. This induced charge is then fed back to the nozzles, amplifying the initial charge separation. The process continues, increasing the voltage difference between the two containers until it's sufficient to cause a spark or discharge.
The initial charge in the Kelvin Water Dropper usually comes from natural, ambient electrical imbalances in the environment or minor asymmetries in the setup of the apparatus itself. Even tiny differences in the shape, alignment, or flow rate of the water droplets can start the process. Once the initial imbalance is established, the apparatus amplifies it through electrostatic induction.
While the Kelvin Water Dropper is primarily a demonstration and educational tool used to illustrate the principles of electrostatics and charge separation, it also has historical importance in the study of electricity. It helps students and enthusiasts understand how charges can be generated and manipulated without mechanical movement or friction, which are common in other types of electrostatic generators.
The Kelvin Water Dropper can generate high voltages, but the overall power output (the product of current and voltage) is quite low. The device is not practical for generating electricity on a scale that would be useful for most applications. Its value lies more in its educational significance and as a demonstration of electrostatic principles rather than as a source of usable power.