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Dielectrics are materials that become polarised when subjected to an electric field. Due to the action of the external electric field, the charges in the molecules move apart from each other, reducing the strength of the electric field in that medium. We have free electrons in metals.
When a conductor is held in an external electric field, the free electrons experience a force as a result of the electric field, resulting in a potential gradient inside the conductor and an induced electric field in the opposite direction of the external electric field. In the case of electrostatics, the total electric field in the bulk of the conductor is zero due to this induced electric field.
Dielectric
Dielectrics are materials that are not conductors. Insulating materials and weak electric current conductors are what they are. Dielectric materials can keep their electrostatic charge while releasing very little heat. Dielectrics include mica, plastics, glass, porcelain, and various metal oxides. It’s also worth noting that even dry air has dielectric properties.
Dielectrics classification
These are of two types:
Polar molecules: Polar Molecules are dielectrics in which the probability of positive and negative molecules colliding is negligible or non-existent. This is due to the fact that they are all asymmetrical in shape. Examples include H2O, CO2, NO2, and other gases. The electric dipole moment of these molecules moves in an unanticipated direction when there is no electric field. As a result, the average dipole moment is zero. If an external electric field exists, the molecules will assemble in the same direction as the field.
Non-Polar Molecule: Unlike polar molecules, non-polar molecules’ positive and negative charge centres do not coincide, i.e., zero. In the molecule, there is no longer any persistent (or intrinsic) dipole moment. O2, N2, H2, and other gases are examples.
Dielectrics properties
The dielectric materials have the following characteristics:
The dielectric materials have a significant energy gap.
The insulating resistance is high and the temperature coefficient of resistance is negative.
The resistivity of the dielectric materials is high.
The electrons’ attraction to the parent nucleus is quite strong.
Because there are no free electrons to transport current, the electrical conductivity of these materials is extremely poor
Factors that affect dielectric polarisation
Electric Field: One of the components that impacts dielectric polarisation is the electric field. Because it is the primary cause of dielectric polarisation.
Electric Field Intensity: The dielectric polarisation will fluctuate depending on the intensity of the electric field. The term “change” merely refers to the length of time that the electric field’s impact lasts.
Heat: Heat isn’t always the determining factor in dielectric polarisation. However, depending on the substance utilised, it may have an impact on dielectric polarisation.
Dielectric polarisation
When a nonpolar molecule is subjected to an external electric field, all protons move in the same direction as the field, while electrons move in the opposite direction. Unless the internal pressures are balanced due to the presence of an electric field, this process will continue. Two charge centres are formed as a result of this. Because they are polarised, we call them the Induced Electric Dipole. The dipole moment is the induced electric dipole moment.
Dielectric When an external electric field is applied to a dielectric substance, polarisation occurs. Charges (both positive and negative) are shifted when an electric field is applied. Dielectric polarisation’s main purpose is to relate macroscopic and microscopic properties.
Applications of dielectrics
Capacitors use dielectrics to improve the amount of energy they can store.
Mineral oil, a dielectric, is utilised as a coolant in the transformer.
In semiconductor devices, high permittivity dielectric materials are used.
Because of their great dielectric strength, porcelain insulators are used to insulate power lines because they can withstand significantly higher voltage before dielectric breakdown.
Conclusion
The medium or the medium’s permittivity determines the strength of the electric field. Vacuum has the strongest electric field. Dielectrics are materials that become polarised when subjected to an electric field. That is, due to the action of the external electric field, the charges in the molecules move apart from each other, reducing the strength of the electric field in that medium.
Polar and non-polar dielectrics are the two types of dielectrics. Polar dielectrics contain an inherent dipole moment, which means that the centre of mass of the negative and positive elements do not coincide, whereas the centre of mass of the negative and positive parts coincide in non-polar dielectrics. When a material is exposed to an external electric field, polarisation occurs, which causes the electric charges to be displaced. The value of the dielectric constant is directly proportional to the extent of polarisation. The permittivity of a conductor is unlimited. In a conductor, the electric field strength is zero.
