In a liquid, the current is carried by ions, which are atoms or molecules that have lost or gained electrons, giving them a net electrical charge. When an electric field is applied to a liquid, these ions are attracted to the oppositely charged electrode and move through the liquid, carrying the current.

In pure water, the concentration of ions is very low, so it is a poor conductor of electricity. However, when impurities such as salts or acids are dissolved in water, the concentration of ions increases and the water becomes a better conductor of electricity.

The conductivity of a liquid is also affected by its temperature. As the temperature of a liquid increases, the ions move more quickly and the conductivity increases.