# Electroviscous effects

Electroviscous effects, in chemistry of colloids and surface chemistry, according to an IUPAC definition,[1] are the effects of the particle surface charge on viscosity of a fluid.

Viscoelectric is an effect by which an electric field near a charged interface influences the structure of the surrounding fluid and affects the viscosity of the fluid.[2]

Kinematic viscosity of a fluid, η, can be expressed as a function of electric potential gradient (electric field), ${\textstyle {\vec {E}}}$, by an equation in the form:

${\displaystyle \eta =\eta _{0}\left(1+f\,\lVert {\vec {E}}\rVert ^{2}\right)}$

where f is the viscoelectric coefficient of the fluid.

The value of f for water (ambient temperature) has been estimated to be (0.5–1.0) × 10−15 V−2 m2.[3]