Unit 11 condensers and dielectric materials

The dielectric of a condenser is one of the three essential parts. It may be found in solid, liquid, or gaseous form or in combinations of these forms in a given condenser.

The simplest form of a condenser consists of two electrodes or plates separated by air, this representing a condenser having a gaseous dielectric. If this imaginary condenser had the air between the plates replaced by a nonconducting liquid, such as transformer oil, and if the distance between the plates were the same as in the first case, the capacitance would be found to have increased several times on account of the oil having a higher value of dielectric constant than air which is usually taken as 1.

The space between the plates being occupied by a solid insulator, a condenser would result, which would be practical, as far as the possibility of constructing it is concerned. It would be found, in this case too, that the capacitance of the condenser was several times larger than when air was the dielectric.

The mechanical construction of either air or liquid dielectric condensers requires the use of a certain amount of solid dielectric for holding the two sets of plates.

There are a great many dielectric or insulating materials available from which one may choose. A material which is very good from the electric standpoint is often found to be poor mechanically or vice versa, air being the gas generally used as a dielectric. Compressed air has been used in some high-voltage condensers, compressed nitrogen and carbon oxide being also in use.

Several kinds of oil have been used in condensers, such as castor oil, cottonseed oil, and transformer oil. More recently electrolytic condensers have come into use in radio equipment for use as filters and by-pass condensers where a large capacitance is required and either a d. c. or pulsating d. c. is applied.

Among the solids to meet the requirements as the condenser dielectric are mica, ceramic materials, and paper. Solid insulators used as mechanical supports in condensers include quartz, glass, porcelain, bakelite, mica, amber, hard rubber, etc.

EXERCISES

1. Find in the text synonyms for:

shape, to demand, to select, viewpoint, to apply, some, sort.

2. Give Russian equivalents for:

as far as ... is concerned, from the point of view, to be available, on the contrary, vice versa, to meet the requirements.

3. Find in the text:

1. Constructions with verbals and analyze them;

2. Conditional sentences.

4. Compose sentences with:

on account of, either ... or, from the standpoint, to some degree (extent), vice versa.

5. Translate into English:

Відомо, що метали є самими гарними провідниками електрики. По суті, усі речовини в рідкому або твердому стані мають певною мірою властивість електричної провідності. Солі, окисли металів і інші речовини є відносно поганими провідниками або ізоляторами. Є багато різних ізоляційних матеріалів. У конденсаторах, наприклад, у якості ізоляторів використовується слюда, скло, стиснене повітря, бурштин, гума й багато інші матеріали.

6. Be ready to speak:

a) about the construction of a condenser; about dielectric

materials.