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| Kinds of Currents 1.As you, certainly, know electric charges in motion constitute a current.2. There are two kinds of current, namely: direct and alternating. 3.A direct current (d.c. for short) flows through a conducting circuit in one direction only.4.It does not change in magnitude.5. It is measured by the quantity of electricity passing through any section of the conductor in one second. 6.By the way, direct current generators produce a direct current. 7.A direct current is, of course, useful and we know the electrical systems in airplane, and in automobile to use direct current. 8.It is also used in research work, in the telephone, in the telegraph, etc. 9.An alternating current (a.c. for short) is a current that changes its direction of flow through a c ircuit. 10.To alternate means to move back and forth. 11.The current flowing first in one direction and then in another, we name it an alternating current.12. An alternating current flows in cycles, the number of cycles per second being called the frequency of the current.13. The frequency of the current is known to be measured in cycles per second. 14.The standard frequency in Russia is 50 c.p.s. (cycles per second). 15. From the above-mentioned, it is clear that a direct current system is useful.16. However, in spite of its usefulness a direct current system has one great disadvantage.17. Namely, there is no economical way by means of which one can increase or decrease its voltage. 18.The alternating current does not know this disadvantage, alternating voltage increasing or decreasing with little loss owing to a transformer. 19.Using a transformer, it is possible to convert power at low voltage into power at high voltage, power at high voltage being also transformed into power at low voltage. 20.Power being transmitted over long distances with less loss at high voltage, it is more economical to increase the voltage for transmission and to decrease it to the voltage which is best suited for the particular use. 21.An alternating current is widely used both in industry and in everyday life. 22.A.c. generators produce alternating current. 23.It was Yablochkov, the great Russian scientist, who first widely applied the alternating current in practice. 24.His electric candle was fed by the a.c, Yablochkov's candle having given the first and most decisive stimulus to the development of the a.c. system, a number of plants began to turn out generators producing the alternating current | 1. , , , , .2. , : . 3. (d.c. ) .4.³ .5. ³ , - , .6. ̳ , .7. , , .8.³ , , .9. (a.c. ) - , . 10. .11. , . 12. , 13.. ³, . 14. 50 15. , .16., .17. , .18. , , . 19. , () () ,() () .20. () , () . 21. , . 22.A.c. . 23. , , . 24. a.c ( , , - (a.c.), , |
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