Introduction
The dielectric constant is a critical concept which is used in the field of electricity. Different materials have a massive property to hold huge electric charges for long durations. This property of the material is called dielectric.
What is Dielectric?
A material that has poor electrical conductivity but owns the capability to store an electrical charge is called dielectric material. There are many dielectric materials like vacuum, metal, air or water. It is important to increase capacitance in a circuit of capacitance in those circuits’ dielectrics play a major role.
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What is Dielectric Constant?
The dielectric constant evaluates the capacity of a dielectric material to reserve energy in an electric field. It is also known as relative permittivity.
- It is defined as the proportion of the permittivity of the material to the permittivity of the free space.
- It also explains the flux density generated at a point in the field due to electric field intensity.
Dielectric Constant Formula
The mathematical expression for the dielectric constant is given below −
K=ϵϵ0K=ϵϵ0
where K is the dielectric constant
ϵϵ is the permittivity of the material
ϵoϵo is the permittivity of the free space
Dielectric Constant Units
It has no unit and dimension as it is a ratio of two like quantities.
Dielectric Constant Symbol
The specific inductive capacity, called the dielectric constant, is symbolised by the Greek letter Kappa, K.
The Theory Behind Dielectric Constant
It is a primary variable needed to specify a capacitor. An electronic device used to store charge is called a capacitor, which is formed by putting a dielectric insulating plate in between the metal conducting plates.
- This dielectric material layer determines the efficiency and capacity of a capacitor to store charge. Thus, it is advised to select the finest dielectric material.
- This property of dielectric is considered important in the working of a capacitor.
- The dielectric constant can also be explained as the ratio of the electric field without a dielectric (E0)(E0) to the resultant electric field with a dielectric (E).
K=E0EK=E0E
- E0E0 is always greater or equal to E. Therefore, the value of the dielectric constant K is always greater than 1.
- More the value of K large amounts of charge will be stored in the capacitor.
- The relation of capacitance of a capacitor with dielectric C and capacitor without dielectric C0C0 is
C=KC0C=KC0
Thus, if dielectric material is filled in the space between the plate of capacitors, then the value of its capacitance will get increased by the value of the dielectric constant.
The formula of capacitance for parallel plate capacitor is
C=Kε0AdC=Kε0Ad
Here,
- C refers to the capacitance of the parallel plate capacitor
- K refers to the dielectric constant
- ε0ε0 refers to the permittivity of free space
- A refers to the area of the parallel plate capacitor
- d is the distance between parallel plates
From the above expression, it is understood that the capacitance can be increased by enhancing the value of the dielectric constant and by reducing the distance between the parallel plates.
Dielectric Constant Value
The value of a dielectric constant is different for distinct dielectric materials that are given below −
| S. No. | Dielectric Material | Dielectric Constant Value |
|---|---|---|
| 1 | Teflon | 2.1 |
| 2 | Concrete | 4.5 |
| 3 | Air | 1.00059 |
| 4 | Vacuum | 1 |
| 5 | Water | 80 |
| 6 | Silicon | 11.68 |
| 7 | Diamond | 5.5 – 10 |
Table-1: Dielectric constant for different dielectric materials
Factors Affecting Dielectric Constant
There are several factors that affect the value of the dielectric constant that are described below −
Temperature
At low temperatures, the adjustment of the molecules of dielectric material is difficult. But if the temperature is increased, there is an increase in the dipole moment of the material which increases the value of the dielectric constant. This temperature at which the dielectric constant starts increasing is referred to as the transition temperature. If the temperature is raised above the transition temperature, then there is a continuous decrease in the dielectric constant.
Frequency
If the frequency of the external voltage is increased, the dielectric constant value turns non-linear.
Applied Voltage
If alternating current voltage is supplied then the value of the dielectric constant will get increased whereas its value gets decreased if the direct current voltage is supplied.
Humidity or Moisture
With the increase in humidity or moisture, the value of the dielectric constant decreases.
Heating Effect
If the dielectric material is heated, there is a motion in the molecules of the material which leads to the dissemination of the energy that is considered a dielectric loss. This loss in the form of heat occurs when a dielectric material is provided with electrical energy.
Structure and Morphology
The dielectric constant is affected by the structure and morphology of the material.
Conclusion
The present tutorial gives a brief description of the dielectric constant which is also known as the historic term used for relative permittivity. For zero frequency the permittivity of the material is regarded as the static or frequency-based variant.
In addition, the factors affecting dielectric constant have been briefly provided. Different expressions of this constant with respect to several physical quantities have been stated in this tutorial. This tutorial may be useful for understanding the permittivity of different dielectric materials.
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