Electroviscosity is a phenomenon in which some liquids change their liquid state when an electrostatic field is applied. Thus, a viscous liquid can become thin due to electroviscosity.
The liquids that react in this way, which are mineral or silicone oils, are so-called suspensions, which are suspensions in which solid particles float in a liquid phase. The particles are very small, ranging in size from 10 nm to 1,000 nm, and remain in suspension due to their small size and their own thermal motion. When an electrostatic field is applied, the particles, although neutral, experience an electrostatic charge. The charge shifts inside create a charge potential on the surface surrounded by oppositely charged ions. This contributes to the stabilization of the solutions.
The viscosity of a liquid is determined by the mobility of its components. If they can move without interference, the state of aggregation is thin. If the particles hinder each other, it is viscous.