Condensed dielectric

Kormer, S.B., Optical Study of the Characteristics of Shock-Compressed Condensed Dielectrics, Soviet Phys. Uspekhi 11 (2), 229-254 (1968). 

All in all, the molecules of a condensed dielectric polarize non-lineeirly in an externally applied electric field E as well as in the molecular field F. Since the latter has a field strength of the order of F s 10 —10 V m , which is two or three orders of magnitude greater than the usually applied external fields F 10 V m , the molecular field is apt to induce large non-linearities in the molecules. The fact should not be neglected if one wishes to have good agreement between experiment and theory. - ... 

According to Frohlich, a pure condensed dielectric consisting of polarizable molecules with a permanent dipole moment p may be formally represented by a continuum permittivity accounting for the molecular polarizability, embedded in the bulk continuum with the effective permittivity 8. The fundamental polarization equation for such a polar dielectrics is... 

Dielectric heating of a material occurs when high-frequency voltage is applied to the material that forms the dielectric of a condenser. Dielectric heating results from the dielectric loss in the material. The dielectric loss is determined by how easily... 

Kormer SB (1968) Optical study of the characteristica of shock-compressed condensed dielectrics. Sov Phys-Uspekhi 11 229-254... 

Dieckmann condensation an intramolecular Claisen condensation, dielectric constant a measure of how well a solvent can insulate opposite charges from one another. 

Dielectric Constant. Dielectric constant or specific inductive capacity (SIC) is both defined and measured by the ratio of the electric capacity of a condenser having that material as the dielectric to the capacity of the same condenser having air as the dielectric. The dielectric constant of vacuum is unity. Dry air has a constant slightly higher but for most practical purposes it is considered as unity. 

Two parallel plates of conducting material separated by an insulation material, called the dielectric, constitutes an electrical condenser. The two plates may be electrically charged by connecting them to a source of direct current potential. The amount of electrical energy that can be stored in this manner is called the capacitance of the condenser, and is a function of the voltage, area of the plates, thickness of the dielectric, and the characteristic property of the dielectric material called dielectric constant. 

The capacitance of a condenser ia terms of its physical dimensions and the dielectric constant of the iasulation is given by the foUowiag equatioa, where C = capacitance ia microfarads, K = dielectric coastant of the iasulatioa, A = area of plates ia square centimeters, and t = thickness of the iasulation ia centimeters. 

If an alternating current potentiaHs appHed to an electrical condenser, each reversal of the potential results ia a reversal of the charge stored ia the coadeaser. There is, therefore, an alternating current apparently flowing through the condenser proportional to the capacitance of the condenser, hence proportional to the dielectric constant of the iasulation material forming the dielectric of the condenser. 

Power factor, like the dielectric constant, is a property that represents a power loss that takes place when a wire insulation becomes the dielectric of a condenser because of a surrounding sheath or other conducting medium. 

Arsenic pentafluoride (arsenic(V) fluoride), AsF, is a colorless gas that condenses to a yellow Hquid its dielectric constant is 12.8 at 20 °C. It is formed by reaction of a mixture of bromine and antimony pentafluoride with arsenic trifluoride. The molecule is a trigonal bipyramid and is somewhat dissociated as indicated by vapor density measurements. 

Locations having low ambient temperature or high humidity may adversely affect the insulation level of the bus system. In this case an ordinary space heater may not be adequate and a separate anti-condensation arrangement may become imperative to dry the condensate and to maintain a high dielectric strength. This may be achieved by ... 

A colourless, odourless, neutral liquid at room temperature with a high dielectric constant. The amount of water present can be determined directly by Karl Fischer titration GLC and NMR have been used to detect unreacted propionic acid. Commercial material of high quality is available, probably from the condensation of anhydrous methylamine with 50% excess of propionic acid. Rapid heating to 120-140° with stirring favours the reaction by removing water either directly or as the ternary xylene azeotrope. The quality of the distillate improves during the distn. 

Figure 6.1. (a) Atom not subject to external electric field. Centre of electron cloud and nucleus coincident, (b) Electron cloud displacement through application of external electric field, (c) Charged condenser plates separated by vacuum, (d) Condenser plates separated by dielectric... 

The influence of a particular dielectric on the capacitance of a condenser is conveniently assessed by the dielectric constant, also known as the relative permittivity or rarely specific inductive capacity. This is defined as the ratio of the relative condenser capacity, using the given material as a dielectric, to the capacity of the same condenser, without dielectric, in a vacuum (or for all practical intents and purposes, air). 

In the dielectric of a condenser the dipole polarisation would increase the polarisation charge and such materials would have a higher dielectric constant than materials whose dielectric constant was only a function of electronic polarisation. 

This polymer first appeared commercially in 1965 (Parylene N Union Carbide). It is prepared by a sequence of reactions initiated by the pyrolysis of p-xylene at 950°C in the presence of steam to give the cyclic dimer. This, when pyrolysed at 550°C, yields monomeric p-xylylene. When the vapour of the monomer condenses on a cool surface it polymerises and the polymer may be stripped off as a free film. This is claimed to have a service life of 10 years at 220°C, and the main interest in it is as a dielectric film. A monochloro-substituted polymer (Parylene C) is also available. With both Parylene materials the polymers have molecular weights of the order of 500 000. 

A capacitor, previously called a condenser, stores electrical energy based on the relationship between voltage (V) and stored charge (Q) in coulombs as shown in the equation C = QU. One farad of capacitance is a coulomb per volt of stored charge. The voltage limit of a capacitor is determined by the breakdown potential of the dielectric material. 

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