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Dielectric Constant- Definition, Formula, Meaning in Chemistry

A dielectric is a substance with low electrical conductivity that also has the ability to store electrical charge (due to Dielectric polarization). As a result, it exhibits only displacement current, making it perfect for use in the construction of a capacitor to store and return electrical energy.

Dielectric Constant Definition and Meaning in Chemistry

This is an important parameter to consider when describing a capacitor. An electronic component called a capacitor is used to store electric charge. A dielectric insulating plate is sandwiched between the metal conducting plates in most cases. The dielectric property of a capacitor is critical to its operation.

The capacitor’s ability to store charge is determined by the dielectric material layer. It’s critical to choose the correct dielectric material. As a result, it can be defined as the ratio of the electric field without a dielectric(E0) to the net field with a dielectric(E).

κ = 𝜺/ 𝜺0


E0 is always bigger than or equal to E in this case. As a result, a dielectric constant’s value is always greater than 1.

More charge can be stored in a capacitor with a higher value of κ.

Dielectric Constant Formula

It is mathematically expressed as:

κ = 𝜺/ 𝜺0


  • κ à dielectric constant
  • 𝜺 à permittivity of the substance
  • 𝜺0 à permittivity of the free space

It is a unitless, dimensionless quantity since it is the ratio of two like entities. The Dielectric Constant, denoted by the Greek letter kappa ‘κ’, is the relative permittivity of a dielectric substance..


Factors Affecting Dielectric Constant

The dielectric constant depends on various factors such as:

  • One of the elements affecting dielectric constant is the frequency of the applied voltage. The value of the dielectric constant becomes non-linear as the frequency of the applied voltage increases.
  • When a direct current voltage is applied, the dielectric constant value decreases, however when an alternating current voltage is applied, the dielectric constant value increases.
  • Temperature: When the temperature is low, the molecules in the dielectric substance have a difficult time aligning. The dipoles in the dielectric material become dominant as the temperature rises, resulting in an increase in the dielectric constant. The transition temperature is the temperature at which something changes from one state to another. If the temperature climbs over the transition temperature, the dielectric constant will gradually drop.
  • Humidity and moisture: As humidity and moisture levels increased, the dielectric material’s strength reduced.
  • Heating effect: Dielectric loss occurs when the dielectric substance is heated. When a material is subjected to an alternating current voltage, dielectric loss is defined as the dissipation of energy in the form of heat due to movement of the molecules in the material. As the substance absorbs electrical energy, this happens.
  • The dielectric constant is also influenced by the material’s structure and shape.
  • The dielectric constant is also affected by the material’s deterioration and weathering.

Dielectric Constant of Vacuum Glass

In general, the dielectric constant is the ratio of a substance’s absolute permittivity to the absolute permittivity of free space. Liquid water has a dielectric constant of roughly 78.4 at room temperature.

Dielectric Constant of Water

In general, the dielectric constant is the ratio of a substance’s absolute permittivity to the absolute permittivity of free space. Glass has a dielectric constant of roughly 5-10 at room temperature.

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Dielectric Constant: FAQs

What is a typical dielectric constant?

2 Constant of Dielectric (ASTM D-150) The dielectric constant is the ratio of the capacitance formed by two plates separated by a material to the capacitance formed by the same plates separated by air. Frequencies less than 1,000 MHz are considered low megahertz.

Can glass be used as dielectric?

Because of their ultrafast discharge speed, good high temperature stability, stable frequency, and environmental friendliness, ferroelectric glass–ceramic materials have been widely used as dielectric materials for energy storage capacitors.

What is dielectric constant of a material?

The dielectric constant is a property of an electrical insulating material (a dielectric) equal to the ratio of the capacitance of a capacitor filled with the supplied material to the capacitance of an identical capacitor in a vacuum without the dielectric material.

What is considered a high dielectric constant?

High dielectric constant materials have a dielectric constant k x 8.854 F/cm greater than that of silicon nitride (k > 7) while low dielectric constant materials have a dielectric constant k less than that of silicon dioxide (k 3.9).

What is a low dielectric constant?

When exposed to an externally produced electric field, a low-k dielectric is an insulating substance that exhibits weak polarisation. Designing low-k materials can be done in a variety of ways, including: Dielectric Constant is low.


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