Temperature

The temperature scale is based on a fixed temperature, that of the triple point of water at which it's solid, liquid and gaseous. Scientists designate the freezing point of water as 273.15 K. It equals exactly 0° on the Celsius temperature scale. The Celsius scale, which is identical to the centigrade scale, gets its name from the name of the 18th-century Swedish astronomer Anders Celsius. He first proposed the use of a scale in which the interval between the freezing and boiling points of water is divided into 100 degrees. By international agreement, the term Celsius has offi­cially replaced centigrade.

One feature of SI is that some units are too large for ordinary use and others too small. To compensate, scientists borrowed and expanded the prefixes for the metric system. Examples are millimeter (mm), kilometer/hour (km/h), megawatt (MW), andpicofarad (pF). The prefixes hecto, deka, deci, and centi are used only rarely, and then usually with meter to express areas and volumes

high-pitched sounds - звуки высокой частоты

sine wave - синусоидальная волна

a.c. - переменный ток

atmospheric noise - атмосферные помехи

fibre optics - оптиковолоконные технологии

immunity - защищенность, невосприимчивость

carrying capacity - пропускная способность

processing -обработка

undersea - подводный

vacuum tube - электронная лампа

varying - меняющееся

auxiliary - вспомогательный

switchboard - коммутатор

made - сделанный

to be referred to as - называться

is based - основан

fixed - фиксированный

triple point - тройная точка

is divided -поделен

has offi­cially replaced - официально заменил

Тексты для студентов-заочников группы (“РТ? 1к. 2с.)

Capacitor

A capacitor is one of the main elements of a circuit. It is used to store electric energy. A capacitor stores electric energy provided that a voltage source is applied to it. The main parts of any capacitor are metal plate and insulators. Its function is to isolate the metal plate and in this way to prevent a short.

There are two common types of capacitors in use nowadays: a fixed capacitor and a variable one. The plates of a fixed capacitor can not be moved. For this reason its capacity does not change. The variable capacitor plates move, its capacity changes. The greater the distance between the plates, the less is the capacitor's capacity. The function of variable capacitors widely used is to vary the frequency in the circuit.

Fixed capacitors have insulators have insulators produced of paper, ceramics and other materials; variable capacitors have air insulators. Paper capacitors are used because of their advantage is their high capacity: it may be higher than 1,000 picofarad.

Besides, electrolyte capacitors are highly in use. They also have a very high capacity: it varies from o.5 to 2,000 micofarad. Their disadvantage is that they change their capacity when the temperature changes only at temperatures not lower than -40 degrees Celsius.

Common troubles in capacitors are an open and a short. A capacitor stops operating and does not store energy in case it has a trouble. It should be substituted by a new one.