● Dielectric Constant
● Dielectric Material
The dielectric constant (symbol ε) is the ratio of the permittivity of a substance to the permittivity of free space. The permittivity expresses the ability of a material to polarize in response to an applied field. It is an expression of the extent to which a material concentrates electric flux, and is the electrical equivalent of relative magnetic permeability.
Both low and high dielectric constants are essential in electronic industries. Low dielectric constant is required basically as insulators. Generally, substances with high dielectric constants break down more easily when subjected to intense electric fields, than materials with low dielectric constants. Materials with low dielectric constants include a perfect vacuum, dry air, and most pure, dry gases such as helium and nitrogen. Materials with moderate dielectric constants include ceramics, distilled water, paper, mica, polyethylene, and glass. Materials with high dielectric constants in general include metal oxides, etc.
dielectric constant (symbol ε)
The dielectric material is a substance that is a poor conductor of electricity, but an efficient supporter of electrostatic fields. If the flow of current between opposite electric charge poles is kept to a minimum while the electrostatic lines of flux are not impeded or interrupted, an electrostatic field can store energy. This property is useful in capacitors, especially at radio frequency. Dielectric materials are also used in the construction of radio-frequency transmission lines.
Traditionally dielectric materials are made from inorganic substances eg. mica and silicon dioxide.
However polymers are gaining wider use as dielectric materials. This is due to the easier process, flexibility, able to tailor made for specific uses and better resistance to chemical attack.
In practice, most dielectric materials are solid, such as
porcelain (ceramic), mica, glass, plastics, and the oxides of various metals.
Some liquids and gases can serve as good dielectric materials. Dry air is an
excellent dielectric, and is used in variable capacitors and some types of
transmission lines. Distilled water is a fair dielectric. A vacuum is an
exceptionally efficient dielectric.