Q.10 Write the different applications of
dielectric.
Ans. Application Of Dielectric: -
Dielectric materials can be
solids, liquids, or gases. In addition, a high vacuum can also be a useful,
lossless dielectric even though its relative dielectric constant is only
unity.Solid dielectrics are perhaps the most commonly used dielectrics in electrical
engineering, and many solids are very good insulators. Some examples include
porcelain, glass, and most plastics. Air, nitrogen and sulfur hexafluoride are
the three most commonly used gaseous dielectrics. The most common use of
dielectric are given as follows -
· It
is used as filler material in capacitor. Which increases the capacitance of the
capacitor.
· It
is also used in dielectric resonator oscillator (DRO) an electronic component
that exhibits resonance for a narrow range of frequencies, generally in the
microwave band.
· Industrial
coatings such as parylene provide a dielectric barrier between the substrate
and its environment.
· Mineral
oil is used extensively inside electrical transformers as a fluid dielectric
and to assist in cooling. Dielectric fluids with higher dielectric constants,
such as electrical grade castor oil, are often used in high voltage capacitors
to help prevent corona discharge and increase capacitance.
· Because
dielectrics resist the flow of electricity, the surface of a dielectric may
retain stranded excess electrical charges. This may occur accidentally when the
dielectric is rubbed (the triboelectric effect). This can be useful, as in a
Van de Graaff generator or electrophorus, or it can be potentially destructive
as in the case of electrostatic discharge.
· Specially
processed dielectrics, called electrets (also known as ferroelectrics), may
retain excess internal charge or “frozen in” polarization. Electrets have a
semipermanent external electric field, and are the electrostatic equivalent to
magnets. Electrets have numerous practical applications in the home and
industry.
· Some
dielectrics can generate a potential difference when subjected to mechanical
stress, or change physical shape if an external voltage is applied across the
material. This property is called piezoelectricity. Piezoelectric materials are
another class of very useful dielectrics.
· Some
ionic crystals and polymer dielectrics exhibit a spontaneous dipole moment
which can be reversed by an externally applied electric field. This behavior is
called the ferroelectric effect. These materials are analogous to the way
ferromagnetic materials behave within an externally applied magnetic field.
Ferroelectric materials often have very high dielectric constants, making them
quite useful for capacitors.
