Water with Excess Electric Charge

Water dropping from a biased metal needle acquires net electric charge that can be stored within a Faraday cup. Positive (negative) water is obtained from a positive (negative) needle, and its charge largely exceeds the Rayleigh limit. Water drops transform into water threads at V < −9.5 kV, even under field strengths much lower than those used in electrospray, electrowetting, or electrospinning experiments. Surface tension of electrified water decreases as the positive or negative charge increases, but its density and viscosity are the same as those of neutral water. Water drops falling in the air through a biased noncontacting metal ring also acquire charge but with opposite sign to the metal potential, in agreement with a recent model for the electrification of insulators or isolated metals, based on charge transfer coupled to water evaporation, adsorption, and desorption.