1. General information on liquids

1.1 Characteristic features of behavior under electrical voltage

Liquids, like most materials (with the exception of metals and alloys), are both dielectrics and insulators. Dielectrics, because the molecules or atoms that make them up can be polarized by an electric field, and insulators, because they are characterized by an electronic structure with a bandgap sufficiently high to ensure that the density of free carriers – electrons and holes – is always negligible.

At low or moderate fields, polarization phenomena are reversible: they give rise to a displacement current (corresponding to the charging and discharging of a capacitor) proportional to the permittivity of the capacitor. $\epsilon ={\epsilon }_0{\epsilon }_{\text{r}}$