Despite not allowing current to flow through them, certain materials however interact with electric fields. Polarization is the mechanism that explains the behaviour of these materials, which are known as dielectrics.
Dielectrics and Polarization
When an insulator is placed in an external field, the dipoles become aligned. Induced surface charges on on insulator establish a polarization field.
What Are Dielectrics?
In contrast to metals, which have free electrons that allow current to flow through them, dielectrics do not conduct electricity. Glass, air, mica, rubber, plastic, and ceramic are classic dielectrics. Capacitors and other electronic components are made of these materials.
Dielectrics can be impacted by electric fields even though they don’t conduct electricity. The electric charges within a dielectric’s atoms or molecules somewhat change when it is exposed to an electric field. This generates tiny electric dipoles throughout the material but does not cause a charge to flow. We called to this entire process as polarization.
What Is Polarization?
When an electric field is present, polarization occurs when the charges within the atoms or molecules of a dielectric material align or separate.
When the dielectric is exposed to the field, the electrons, which are the negative charges, are pushed slightly in the opposite direction, while the nuclei, which are the positive charges, are pulled slightly in the field’s direction.
Every molecule or atom thus turns into a dipole, a system having a positive and a negative end. These tiny dipoles have a tendency to line up with the electric field outside. Dielectrics can be divided into two primary categories based on their inherent structure:
1. Polar Dielectrics:
Positive and negative charges naturally separate because these molecules already have a permanent dipole moment. An excellent illustration is water (H2O). These dipoles have a random orientation when there is no electric field present. The dipoles line up with the electric field when it is applied.
2. Non-Polar Dielectrics:
There is no inherent dipole moment in these compounds. However, the charges within them somewhat move when an electric field is applied, creating a dipole moment. We refer to this as induced polarization.
Effect of Dielectrics in a Capacitor
An apparatus that stores electric charge is a capacitor. Normally, it is made up of two parallel metal plates separated by air or another dielectric.
More charge may be stored for the same applied voltage when a dielectric is positioned between the plates because it lowers the electric field between them. This indicates that the capacitor’s capacitance rises.
The material’s relative permittivity (εr) or dielectric constant determines the rise. A material’s ability to increase capacitance increases with its dielectric constant.
Important Terms to Know
Dielectric Constant (K or εr): It tells us how much a dielectric can reduce the electric field compared to vacuum. For vacuum, εr = 1.
Polarization (P): It is a vector quantity that shows the dipole moment per unit volume of the dielectric.
Electric Susceptibility (χe): It measures how easily a dielectric gets polarised. It is related to the dielectric constant by the formula: εr = 1 + χe
Induced Dipole Moment: A dipole moment that forms when non-polar molecules are placed in an electric field.
Summary
Despite not conducting electricity, dielectrics are insulators that become polarised in response to electric fields. This polarisation has an impact on the material’s internal electric field and is essential for components like capacitors.
Knowing how electric fields behave in actual materials, particularly in electronics and communication systems, requires an understanding of dielectrics and polarisation.
A dielectric is an insulating substance that can be impacted by an electric field but does not let electric current to pass through it. Mica, glass, plastic, and air are typical examples.
Electric dipoles are produced when the charges within a dielectric’s molecules or atoms slightly move when it is exposed to an electric field. Polarisation is the term for this procedure.
The alignment or formation of electric dipoles within a dielectric substance upon exposure to an electric field is referred to as polarisation. As a result, the material’s internal effective electric field is reduced.
Even in the absence of an electric field, polar dielectrics (like water) have persistent dipole moments.
• Although non-polar dielectrics don’t naturally contain dipoles, they can be made to do so by an electric field.
Even in the absence of an electric field, polar dielectrics (like water) have persistent dipole moments.
• Although non-polar dielectrics don’t naturally contain dipoles, they can be made to do so by an electric field.