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ВАРИАНТ 91. Прочтите, перепишите и письменно переведите текст ELECTRIC CURRENT The electric current is a quantity of electrons flowing in a circuit per second of time. The unit of measure for current is ampere. If one coulomb passes a point in a circuit per second then the current strength is 1 ampere. The symbol for current is I. The current which flows along wires consists of moving electrons. The electrons move along the circuit because the e .m. f. drives them. The current is directly proportional to the e. m. f. In addition to traveling through solids, however, the electric current can flow through liquids as well and even through gases. In both cases it produces some most important effects to meet industrial requirements. Some liquids, such as melted metals for example, conduct current without any change to themselves. Others, called electrolytes, are found to change greatly when the current passes through them. When the electrons flow in one direction only, the current is known to be d. c., that is, direct current. The simplest source of power for the direct current is a battery, for a battery pushes the electrons in the same direction all the time (i.e., from the negatively charged terminal to the positively charged terminal). The letters a. c. stand for alternating current. The current under consideration flows first in one direction and then in the opposite one. The a. c. used for power and lighting purposes is assumed to go through 50 cycles in one second. One of the great advantages of a. c. is the ease with which power at low voltage can be changed into an almost similar amount of power at high voltage and vice versa. Hence, on the one hand alternating voltage is increased when it is necessary for long -distance transmission and, on the other hand, one can decrease it to meet industrial requirements as well as to operate various devices at home. Although there are numerous cases when d. c. is required, at least 90 per cent of electrical energy to be generated at present is a. c. In fact, it finds wide application for lighting, heating, industrial, and some other purposes. 2. Письменно переведите следующие слова и выражения из текста на английский язык: 1) течь, протекать; 2) цепь, схема; 3) единица измерения; 4) провод; 5) электродвижущая сила; 6) твердое тело; 7) жидкость; 8) проводить (ток); 9) источник энергии; 10) постоянный ток; 11) переменный ток; 12) напряжение. 3. Письменно переведите выражения на русский язык: 1) to meet industrial requirements; 2) melted metals; 3) to push in the same direction; 4) negatively (positively) charged terminal; 5) power and lightning purposes; 6) long-distance transmission; 7) to operate devices; 8) to find wide application. 4. Перепишите предложения, переведите их и отметьте знаком «+», если предложение верное, и знаком «-», если предложение неверное по смыслу. 1. The symbol for current is I. 2. The electric current can flow only through liquids. 3. The current can be of two types: direct current and alternating current. 4. The alternating current flows in one direction. 5. A battery is the simplest source of power for the direct current. 6. Direct current finds wider application than alternating current. 7. Electrolytes don’t change greatly when current passes through them.
ВАРИАНТ 101. Прочтите, перепишите и письменно переведите текст CONDUCTORS AND INSULATORSAll substances have some ability of conducting the electric current, however, they differ greatly in the ease with which the current can pass through them. Solid metals conduct electricity with ease while non-metals do not allow it to flow freely. Thus, there are conductors and insulators. What do the terms "conductors" and "insulators" mean? This difference is expressed by what is called electrical conductivity of the body. It depends upon the atomic constitution of the body. Substances through which electricity is easily transmitted are called conductors. Any material that strongly resists the electric current flow is known as an insulator. Conductance, that is the conductor's ability of passing electric charges, depends on the four factors: the size of the wire used, its length and temperature as well as the kind of material to be employed. A large conductor will carry the current more readily than a thinner one. To flow through a short conductor is certainly easier for the current than through a long one in spite of their being made of similar material. Hence, the longer the wire, the greater is its opposition, that is resistance, to the passage of current. There is a great difference in the conducting ability of various substances. Almost all metals are good electric current conductors. The best conductors are silver, copper, gold and aluminum. Nevertheless, copper carries the current more freely than iron; and silver, in its turn, is a better conductor than copper. Copper is the most widely used conductor. The electrically operated devices are connected to the wall socket by copper wires. A material which resists the flow of the electric current is called an insulator. The higher the opposition is, the better the insulator is. There are many kinds of insulation used to cover the wires. The kind used depends upon the purposes the wire or cord is meant for. The insulating materials generally used to cover the wires are rubber, asbestos, glass, plastics and others. The best insulators are oil, rubber and glass. Rubber covered with cotton, or rubber alone is the insulating material usually used to cover desk lamp cords and radio cords. Glass is the insulator to be often seen on the poles that carry the telephone wires in city streets. Glass insulator strings are usually suspended from the towers of high voltage transmission lines. One of the most important insulators of all, however, is air. That is why power transmission line wires are bare wires depending on air to keep the current from leaking off. 2. Письменно составьте предложения, основываясь на содержание текста. Предложения письменно переведите.
3. Повторите тему «Предлоги» и письменно выполните упражнение. Вставьте предлоги, где необходимо и запишите предложения. Переведите предложения. 1. My mother is afraid ... rats. 2. "What do you complain ...?" asked the doctor. 3. Don't enter ... the room. 4. What are you laughing ... ? 5. They did not want to listen ... me. 6. Wait ... me. I'll be back ... a few minutes. 7. Yesterday the teacher spoke ... us about the architecture ... St. Petersburg. 8. My grandmother often complains ... headache. 9. I am sorry, Г cannot speak ... you now, the professor is waiting ... me. I must go ... the institute and explain ... him some details ... our work. Come ... the evening, I shall listen ... you very attentively and answer ... all your questions. 10. ... nine o'clock the lecturer entered ... the hall, walked up ... the table, put his bag ... it, looked .... everybody and began his lecture. The lecture, as all the lectures ... this professor, was very interesting, and the students listened ... him with great attention. 11. Turn ... the corner ... the house and look ... the flowers grown ... my mother: aren't they beautiful? 12. He was an excellent pupil, and the teachers never complained ... him. |
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