Dielectric Constant

What Is Dielectric Constant?

Many materials possess a tremendous property to hold their electrical charge for long intervals and in large quantities as well. Such property of materials refers to dielectric property. Many students get confused with the term dielectric constant, property, and often ask what is relative permittivityThis guide is beneficial to understand the meaning and factors affecting the dielectric constant. 


What Are Dielectric Materials?

Dielectric materials have weak electrical conductivity but possess the ability to store an electrical charge. There are several dielectric materials, including vacuum, air, and more. The values of dielectric constants of some dielectric materials include:

  • For air- 1.00059

  • For glass- 3.8-14.5

  • For paper- 3.6

  • For vacuum- 1.00

  • For PVC- 4.0 


What Is Meant By Dielectric Constant?

The dielectric constant of any substance refers to the relative permittivity of the dielectric substance. It is the proportion of the permittivity of the material to the permittivity of the free space. Mathematically, the dielectric constant can be expressed as:

K = \[\frac{\epsilon }{\epsilon_{0} }\]

where K refers to Dielectric constant

             \[\epsilon\] refers to the permittivity of the substance

             \[\epsilon_{0}\] is defined as the permittivity of the free space


Dielectric Constant Theory

Many students ask what the meaning of dielectric constant is. In order to understand the meaning of dielectric constant, it’s crucial to first understand the theory behind it. Dielectric constant serves as the major factor required to describe a capacitor. A capacitor is an electronic device built by inserting a dielectric insulating plate in-between the metal conducting plates. It’s the layer made from a dielectric material that decides if a capacitor can store a high charge or not. That’s why it is essential to choose the best dielectric material depending on the dielectric property. 

From the dielectric constant formula:

K = \[\frac{\epsilon }{\epsilon_{0} }\], we get the value of relative permittivity of free space is always greater than or equal to relative permittivity of substance. Hence, the value of the dielectric constant (K) is always either equal to greater than 1. 


What Does a High Dielectric Constant Mean?

The high value of the dielectric constant means the value of capacitance can be maximised. It can be seen from the capacitance formula in the parallel plate capacitor:

C = K\[\epsilon_{0}\]A/d

where K refers to the dielectric constant

C refers to the capacitance of a parallel plate capacitor.

A refers to the area of parallel conducting plates

\[\epsilon_{0}\] is defined as permittivity of free space

d refers to the separation between parallel conducting plates

Hence, from this formula, it’s clear that there are two ways to increase the value of capacitance. The first is to decrease the separation between parallel conducting plates, and the second is to enhance the dielectric constant value. 


What Do You Mean By Dielectric Constant Equation?

According to the dielectric constant equation:

K = \[\frac{\epsilon }{\epsilon_{0} }\]

K is the ratio of two entities with the same dimension. Hence, the dielectric constant is a unitless and dimensionless quantity. 


What Factors Affect The Value of The Dielectric Constant?

After knowing what is dielectric constantthere come different factors that affect the dielectric constant value such as:

  • Temperature: The arrangement of molecules in the dielectric material is tough at the low temperature. However, with the increase in temperature, the dipoles moment increases, and hence there is a rise in the dielectric constant value. The temperature at which the dielectric constant starts increasing refers to the transition temperature. Moreover, if the temperature goes above the transition temperature, the dielectric constant will start decreasing. 

  • Heating Effect: The students asking what is dielectric property can understand from the fact that on heating any dielectric material, there is a dielectric loss. It is due to the dielectric property of the material due to which whenever there is any movement of molecules inside the material, there is the dissipation of energy. When the dielectric material absorbs electrical energy, it dissipates energy in the form of heat.

  • Applied Voltage: The value of the dielectric constant decreases in the presence of a direct current voltage. However, the dielectric constant value increases when an alternating current voltage is applied. 

  • Frequency: The frequency of the applied voltage serves as one of the critical factors that affect the dielectric constant to a great extent. Whenever there is an increase in the frequency of the external voltage applied, the dielectric constant value becomes non-linear. 

  • Humidity and Moisture: When there is an increase in humidity or moisture, there is a decrease in the strength of dielectric material. 

FAQs (Frequently Asked Questions)

1. What is the Dielectric Constant of Water?

Ans: Water is a dielectric material due to polarisation. The higher polar molecules of water keep rotating, and thus it is an electric dipole. We generally consider it as dielectric because of high permittivity value at 20 degrees C. The dielectric constant of water is still very high but we do not use it in the condenser. It is because of the presence of natural salts in the water. It has the presence of loosely bound and free-electron molecules present in water. 

2. How to Calculate the Dielectric Constant?

Ans: The dielectric constant is related to the polarizability of the material. It is defined by the ratio of electric permeability of the material by the electric permeability in free space. Hence we also call it relative permittivity of the material. However, this dielectric constant does not have any dimensions as it is given by the division of two similar entities. This constant defines the energy that could be stored in the material when we supply voltage to it. However, in the end, the electric field is reduced when it reaches polarization.