Difference between Dielectric and Insulator

An electrical insulator is a material that does not allow the flow of electric current through them. On the other hand, a dielectric is an electrical insulator that can be polarized on the application of an electric field.

The major difference between an insulator and a dielectric is that an insulator opposes the flow of electrons or charges while the dielectric stores the electric charges. Dielectric materials can be polarized while insulators cannot be polarized. Dielectric materials have a high value of dielectric constant while insulators have a low value of dielectric constant. Let’s see the actual difference between dielectric and insulator.

Difference between Dielectric and Insulator in tabular form

Dielectric Insulator
Dielectric is the material that can store electric charges or they are the materials in which an electric field can develop with the minimum loss of energy. Insulator is the material that has low or zero electrical conductivity and they can create obstruction in the flow of electric current.
They can be polarized when an electric field is applied across them. Insulators can not be polarized like the dielectrics in the presence of electric field.
They have a high value of dielectric constant. The dielectric constant of insulators is quite low.
The bond that exists in the dielectric material is weaker than the insulator. A strong covalent bond exists in the insulators.
The dielectric materials have the ability to store the charge. Insulators do not have the ability to store the charge like the dielectrics instead they act as a barrier for the flow of charge or they provide obstruction to the flow of current.

What is dielectric?

Dielectric is a type of insulator that has some amount of free electrons. When an electric field is applied across the dielectric substance it gets polarized. Polarization is the phenomenon through which the positive and negative charges of the substance move to the opposite directions. The net effect of the field decreases due to the polarization.

The storage and dissipation of energy are the key features of dielectric material. Ideal dielectrics offer zero conductivity. The most common and simplest example of dielectric is a capacitor. The surface area of the capacitor increases due to polarization among the plates of the capacitor.

When a dielectric is being placed in an external electric field, there is no movement of electric charges as it is in the case of conductors, but there is just a slight shift from their average equilibrium position causing dielectric polarization. It is due to this dielectric polarization that positive charges are displaced in the direction of the field and negative charges are shifted in the opposite direction. Because of this shifting, an internal electric field is created, which reduces the overall electric field within the dielectric itself.

The bond which exists between the dielectric substances is weak. The dielectric constant defines the storing capacity of the substance. Since the dielectric substances possess the ability to store the charge they have a high value of dielectric constant. Some of the common examples of dielectric materials are vacuum, distilled water, dry air etc.

What is insulator?

These are the materials that do not allow the electric current to pass through them. Insulators can also be defined as materials that have less conductivity and creates hindrance in the flow of electrons. Unlike dielectric materials, insulators can not be polarized. A strong covalent bond exists between the molecules of the dielectric.

The value of the dielectric constant is less for the insulators. Unlike dielectrics, insulators do not store any electric charge. The energy gap between the valence band and conduction band is very high for the insulators. The insulating materials do not have any free electron because their molecules have a strong covalent bond. The resistivity of insulators is greatest among conductors, semiconductors and insulators. Resistivity is the property of the material by which the material opposes the flow of current.

Insulators have very high resistance which further decreases with temperature. Since there are no electrons or holes in the insulator, therefore insulators do not conduct electric current. The examples for insulators include paper, rubber, plastic, etc.


From the above discussion, we have concluded that dielectric is the insulator materials that store electrical energy while insulators are the materials that have zero electrical conductivity or they offer hindrance to the flow of electric current.

Dielectrics can be polarized when an electric field is applied across them while insulators can not be polarized in the presence of the electric field. The bond that exists in the dielectric material is weaker while a strong covalent bond exists in the insulators. The examples of dielectric are vacuum, dry air, distilled water etc. while the examples of insulators are plastic, mica, cotton etc.

Deepak Yadav
Aligarh Muslim University, Aligarh


1. https://www.theengineeringknowledge.com/difference-between-dielectric-insulator
2. https://circuitglobe.com/difference-between-dielectric-and-insulator.html

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