Dielectric

An insulator or a particularly poor conductor of electric current, when put in an electric field, dielectrics conduct almost minimal current because, unlike metals, they contain no loosely connected or free electrons that can drift through the substance. Instead, electric polarisation takes place. Positive charges in the dielectric are displaced minutely in the direction of the electric field, whereas negative charges are displaced minutely in the opposite direction. This little charge separation or polarisation decreases the electric field within the dielectric.

Other electrical phenomena are influenced by the presence of dielectric substances. The force between two electric charges in a dielectric medium is smaller than in a vacuum, but the amount of energy stored in an electric field per unit volume of a dielectric medium is larger. A capacitor filled with a dielectric has a higher capacitance than a vacuum capacitor. In a large or macroscopic scale, the effects of the dielectric on electrical phenomena are explained using terms such as dielectric constant, permittivity and electric polarization.

What is dielectric? 

A dielectric material is a substance that conducts electricity poorly but efficiently supports electrostatic fields. 

An electrostatic field can store energy if the flow of current between opposite electric charge poles is kept to a minimum and the electrostatic lines of flux are not obstructed or interrupted. This feature is very useful in capacitors at radio frequencies. Radio-frequency transmission lines are also constructed with dielectric materials.

The majority of dielectric materials are solid in phase. Porcelain (ceramic), mica, glass, polymers and metal oxides are just a few examples. 

Dielectric materials can be found in some liquids and gases. Dry air is a good dielectric material that is utilised in variable capacitors and some transmission lines. Distilled water has a good dielectric property. A vacuum is a dielectric that is extremely efficient.

Properties of dielectric material

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 shift in the opposite direction of the applied electric field. Dielectric polarisation arises as a result of this. 

Electric charges do not flow through the substance in general. The dielectric field is reduced by polarisation. 

William Whewell coined the phrase “dielectric.” A perfect dielectric substance has no electrical conductivity. A dielectric, like an ideal capacitor, stores and dissipates electrical energy. Electric susceptibility, dielectric polarisation, dielectric dispersion, dielectric relaxation, tunability and many other properties are among the most important that a dielectric shows.

Difference types of Dielectric Material

Dielectric materials include vacuum, solids, liquids and gases. 

Ceramics, paper, mica, glass and other solid dielectric materials are examples. 

Distilled water, transformer oil and other liquid dielectric compounds are examples. 

Nitrogen, dry air, helium, metal oxides and other gas dielectrics are examples. A dielectric is also a perfect vacuum.

Application of dielectric material

Dielectrics are widely used in the manufacture of capacitors. These can store energy in the electric field between the plates, filter out noise from signals as part of a resonant circuit and send a burst of power to another component, among other things. 

Some applications of dielectrics rely on their electrically insulating properties rather than ability to store charge, so high electrical resistivity and low dielectric loss are the most desirable properties here. 

The most obvious of these uses is insulation for wires, cables etc., but there are also applications in sensor devices. For example, it is possible to make a type of strain gauge by evaporating a small amount of metal onto the surface of a thin sheet of dielectric material.

Dielectric Charging

When large electric fields are placed across the thin dielectric layer of a capacitor or when it is subjected to ionising radiation, dielectric charging occurs. Charging of the dielectric in RF MEMS switches with a dielectric is a big issue, especially when the capacitive RF MEMS switch is in the down position, touching the dielectric. Charging causes a change in the pull-in and pull-out voltages, which eventually leads to device stiction. Charges that accumulate near actuation electrodes or in the substrate might cause problems for resonators.

Conclusion

Positive charges in the dielectric are displaced minutely in the direction of the electric field, whereas negative charges are displaced minutely in the opposite direction. The force between two electric charges in a dielectric medium is smaller than in a vacuum, but the amount of energy stored in an electric field per unit volume of a dielectric medium is larger. On a large or macroscopic scale, the effects of the dielectric on electrical phenomena are explained using terms such as dielectric constant, permittivity and electric polarization. The majority of dielectric materials are solid in practice. Properties of dielectric material when positive charges in dielectric materials are exposed to an electric field, they are displaced in the direction of the applied electric field.