Unit 3. Capacitors
Vocabulary
advantage преимущество
besides кроме того
capacitor конденсатор
disadvantage недостаток
distance расстояние
fixed capacitor конденсатор постоянной емкости
for this reason по этой причине
to move двигать(ся), перемещать(ся)
open обрыв, разрыв
part часть
plate анод
to prevent предотвращать
reason причина
to smooth сглаживать
to store charge накапливать заряд
variable capacitor конденсатор переменной емкости
Text
A capacitor is one of the main elements of a circuit. It stores electric
charge. A capacitor stores electric energy provided that a voltage source is applied to it. Capacitors are used to smooth varying DC supplies by acting as a reservoir of charge. They are also used in filter circuits because ca- pacitors easily pass AC signals but they block DC signals.
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Capacitance is a measure of a capacitor’s ability to store charge.
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The main parts of a capacitor are metal plates and insulators. The function of insulators is to isolate the metal plates and in this way to prevent a short.
Two common types of capacitors in use
nowadays are a fixed capacitor and a variable one. The plates of a fixed capacitor cannot be moved; for this reason its capacitance does not change. The plates of a variable capacitor move; its capacitance changes. The greater the distance between the plates, the less is the capacitance of a ca- pacitor. Variable capacitors are commonly used by radiomen; their func- tion is to vary the frequency in the circuit. Fixed capacitors are used in tel-
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Fixed capacitors have insulators pro- duced of paper, ceramics and other materials; variable capacitors have air insulators. Paper capacitors are commonly used in radio and electronics; their advantage is their high ca- pacitance, it may be higher than 1,000 pico- farad.
Besides, electrolyte capacitors are highly in use. They also have a very high capacitance; it varies from 0.5 to 2,000 microfarad. Their disad- vantage is that they change their capacitance when the temperature chang- es. They can operate without a change only at temperatures not lower than
-40° C.
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. A capaci- tor with a trouble should be substituted by a new one.