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Dielectrics – A dielectric (also known as a dielectric substance or a dielectric medium) is an electrical insulator that can be polarised by an applied electric field in electromagnetism. When an electric field is applied to a dielectric material, electric charges do not flow through it as they would in an electrical conductor because there are no loosely bound or free electrons to drift through it; instead, they shift slightly from their average equilibrium positions, resulting in dielectric polarisation. Positive charges are shifted in the direction of the field by dielectric polarisation, while negative charges shift in the opposite way (for example, if the field is moving parallel to the positive x-axis, the negative charges will shift in the negative x-direction).
What is the difference between dielectrics and insulators?
Dielectrics are materials that are extremely poor conductors of electric current in general. They’re essentially insulators with no free electrons. When an electric field is supplied to a dielectric, it is easily polarised. As a result, their behaviour in an electric field is completely different from that of conductors, as the following discussion will demonstrate.
Polarization of Dielectrics
The molecules that make up a dielectric might be polar or non-polar. However, the net impact of an external field is nearly the same, i.e., the external field will compel the molecules to align their dipole moments in the direction of the external field.
Consider a dielectric slab in the presence of an electric field acting in the direction depicted in the diagram. The charge arrangement within the dielectric molecules in the electric field is depicted in the diagram. Positive charges travel in the field’s direction, while negative charges travel in the opposite direction. To put it another way, the electric dipoles align themselves with the field’s direction. The entire dielectric and its molecules are said to be polarised in this state.
Polarisation is defined as the alignment of the dipole moments of permanent or induced dipoles with the direction of the applied electric field.
There is an excess negative charge in one of the two extremely thin surface layers shown by shaded patches, and an excess equal positive charge in the other.
These layers are responsible for the induced charges on the dielectric surfaces. These charges are not unattached; instead, they are each bound to a molecule on or near the surface. These charges are known as bound charges or false charges because of this. The net charge per unit volume within the remaining dielectric remains zero. As a result, even though the dielectric is polarised, it is electrically neutral as a whole.
The Uses of Dielectric Materials
- Dielectrics are utilised to store energy in capacitors.
- In the Oscillator Dielectric Resonator, the ceramic dielectric is used.
- To improve the performance of a semiconductor device, high permittivity dielectric materials are used.
- Mineral oils are used in electrical transformers as a dielectric liquid and to aid in the cooling process.
- Electrets are a type of dielectric material that has been carefully processed to act as an electrostatic analogue of magnets.
- Plastic films were employed as films in a number of applications, including condenser insulation between foils and rotating electric machine slot insulation.
- Transformers, earth reactors, shunt reactors, rheostats, and other devices use liquid dielectrics, primarily hydrocarbon mineral oils, as an insulating and cooling medium.
What are the different types of dielectric properties?
Dielectric stores and discharges electric energy in the same way that an ideal capacitor does. Electric susceptibility, dielectric polarisation, dielectric dispersion, dielectric relaxation, and tunability are some of the most important features of dielectric materials.
Susceptibility to Electricity:
When a dielectric substance is exposed to an electric field, its susceptibility to polarisation is measured. The electrical permeability of a substance is also determined by this amount.
Polarization of the dielectric medium:
The negative and positive charge separation within a system is measured by an electric dipole moment. Dielectric qualities arise from the relationship between a dipole’s moment (M) and the electric field (E). The atom returns to its native state when the electric field is removed. It takes an exponential amount of time to decay. The relaxation time is the time it takes for an atom to return to its original state.
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FAQs
Explain what makes all insulators dielectric?
Dielectrics aren't all insulators. An insulator must have a high dielectric constant, high-temperature stability, dielectric power, low loss factor, high storage stability, acceptable frequency response, and be adaptable to industrial processes in order to be considered a good dielectric. Electronic high-frequency circuits require dielectrics as well. The electrical or magnetic properties of a material can be determined by measuring the dielectric properties of that material.
What's the Difference Between a Dielectric Material and an Insulator?
Not all insulators are dielectrics, and not all dielectrics are insulators. Insulators are compounds that are supposed to prevent electricity from flowing through them. The availability of free electrons determines whether material or substance is a conductor or an insulator. Because there are no free electrons in insulators, electricity cannot move through them. Dielectrics, on the other hand, are substances that have the same properties as insulators but can be polarised. Although dielectrics do not allow an electric current to travel through them, they do allow electric fields to do so. The dielectric medium, unlike insulators, has a high dielectric constant. That is why capacitors are made from them.
What is dielectric materials' electric susceptibility?
A dielectric material's electric susceptibility e is a measurement of how quickly it polarises in response to an electric field. This, in turn, defines the material's electric permittivity, which affects a variety of other phenomena in that medium, ranging from capacitor capacitance to the speed of light.
In electrical materials, what is dielectric polarisation?
When positive charges in dielectric materials are exposed to an electric field, they are displaced in the direction of the applied electric field. Negative charges are redistributed in the opposite direction as the electric field is applied. Dielectric polarization arises as a result of this.
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