What is the difference between a dielectric and an insulator?

Dielectrics and insulators are distinguished primarily by their applications. One of the main differences is that a dielectric can store electrical energy by becoming polarized in an electric field, whereas an insulator resists the flow of electrons to prevent current conduction. Other key differences between them are outlined in the comparison chart below.

Definition of Dielectric

A dielectric material is a type of insulator that contains few or no free electrons. When subjected to an electric field, it becomes polarized—a property in which the positive and negative charges within the material shift slightly in opposite directions. This polarization reduces the net electric field within the material, enabling it to store electrical energy.

Energy Storage and Dissipation in Dielectrics

The ability to store and dissipate electrical energy are key characteristics of dielectric materials. An ideal (perfect) dielectric has zero electrical conductivity. A common application of dielectrics is in capacitors. In a parallel-plate capacitor, the dielectric material placed between the plates becomes polarized, which increases the effective capacitance by reducing the electric field for a given charge.

Definition of Insulator

An insulator is a material that does not allow electric current to flow through it. Insulating materials lack free electrons because their atoms are bound together by strong covalent bonds. As a result, they exhibit very high electrical resistivity compared to other materials. Resistivity is an intrinsic property that indicates a material's strong opposition to the flow of electric charge.

Ebonite, paper, wood, and plastic are common examples of insulators.Almost all insulators can behave as dielectrics, but not all dielectrics are used primarily as insulators.