Explanation:
In pure dielectrics, the parameter that is zero is conductivity.

Dielectric Materials:
Dielectric materials are non-conductive materials that are used to separate conducting materials or to insulate conductors from each other. They are commonly used in capacitors, transformers, and other electrical devices.

Conductivity:
Conductivity, denoted by σ, is a measure of a material's ability to conduct electric current. It is the reciprocal of resistivity. Conductivity is a property of conducting materials, such as metals, which have a high number of free electrons that can easily move and carry electric charge.

Pure Dielectric Materials:
Pure dielectric materials, also known as insulators, have a very low conductivity. They do not have free electrons that can move and conduct electric current. In pure dielectrics, the atoms are tightly bound and do not allow the passage of electric charges easily.

Zero Conductivity in Pure Dielectrics:
In pure dielectrics, the parameter that is zero is conductivity. This means that pure dielectric materials have no ability to conduct electric current. They act as electrical insulators and do not allow the flow of electric charges through them.

Importance of Zero Conductivity:
The zero conductivity of pure dielectrics is important in various electrical applications. Some of the key reasons include:

1. Insulation: Pure dielectrics provide excellent insulation properties, allowing them to separate conducting materials and prevent the flow of electric current between them.

2. Capacitors: Pure dielectrics are used as the insulating material between the conductive plates of capacitors. The absence of conductivity ensures that the stored charge remains isolated and does not leak.

3. Electric Safety: Pure dielectric materials are used in electrical wiring and cables to provide insulation and prevent electrical shocks. The zero conductivity ensures that the electric current does not flow through the insulation material.

Conclusion:
In pure dielectrics, the parameter that is zero is conductivity. Pure dielectric materials have no ability to conduct electric current, making them excellent insulators in various electrical applications.