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The Concept of Electrical Current
In the beginning of the 17th century Sir William Gilbert discovered that many substances could be electrified by friction. Gilbert named this effect «electric» after the world «electron» - the Greek name for amber. In 1756 the great Russian scientist M. V. Lomonosov was the first to make theoretical analysis of electrical phenomena.
At present the nature of electrification is explanted by the electron theory. According to the modern theory all matter is composed of atoms or tiny particles. There are many kinds of atoms. Each atom consists of a nucleus, a small positively charged mass and a number of lighter negatively charged particles called electrons, which revolve around the nucleus. Normally each atom of a substance is electrically neutral, or it has equal amounts of negative and positive charges, i.e. produces no electrical effects. If the number of negative charges is not equal to the number of positive charges, the matter will produce electrical effects.
When an electric charge is at rest it is spoken of as static electricity, but when it is in motion it is referred to as an electric current. In most cases, an electric current is described as a flow of electric charges along a conductor.
Not all substances are good conductors of electricity, as a general rule metals are good conductors of electricity, whereas nonmetals are poor conductors. The poorest of conductors are commonly called insulators or nonconductors. There are a large number of substances that are neither good conductors of electricity nor good insulators. These substances are called semi-conductors. An electric current which flows in the same direction through a conductor or a current which does not change its polarity is called a direct current or a continuous current. Its abbreviation is D. C. An alternating current (A. C.) flows first in one direction and then in the other.
An electric circuit is a path through which an electric current flows. This is a complete path along which electrons can transmit their charges. An electric circuit includes a battery, generator, or magnetic means for producting current flow. Some portion of the circuit is made to do useful work.
The circuit is said to be open when no charges can move due to a break in the path. The circuit is said to be closed when no break exists-when switches are closed and all connections are properly made.
Special symbols are used to show electrical systems. There is a wide range of these symbols. There are some of them which are used when we draw circuits. And now look at the diagram of series and parallel arrangements.
Words to the text
1) insulator-изолятор
2) substance-вещество, материя
3) friction-трение, сцепление
4) nucleus-ядро, ячейка
5) amount-сумма, количество
6) charge-заряд, загрузка
7) rest-покой, отдых
8) motion-движение
9) flow-поток, течение
10) circuit-цепь, кругооборот
11) current-течение, ток
12) path-путь, дорожка, линия
13) break-прорыв, интервал, перелом
14) To discover-открывать
15) To make-делать
16) To explain-объяснять
17) To consist-состоять из
18) To revolve-вращаться
19) To produce-производить
20) To transmit-передавать
21) To include-включать
22) To exist-существовать
23) To use-использовать
24) Tiny-маленький, крошечный
25) Light-легкий, светлый
26) Equal-равный
27) Poor-бедный, слабый
28) Continuous-непрерывный, постоянный
29) Wide-широкий
30) Alternating-переменный
Найдите в тексте
а) интернационализмы б) ложные друзья переводчика
Дайте краткие определения следующих понятий:
Static electricity
Electric current
Direct current
Alternating current
Electric circuit
An open circuit
A closed circuit
An electrical phenomenon
An electron theory
Positive charges
Negative charges
Conductors of electricity
Special symbols
Batteries
An Italian scientist Alessandro Volta made a` lot of experiments with electricity. Batteries as sources of electrical energy are the result of his experiments.
Today battery cells are produced in two common forms: dry cells, used in flashlights, portable radios, clocks, cameras and (well) wet cells, used in automobiles, airplanes, boats.
The voltaic cell is composed of three parts: a pair of dissimilar metal plates called electrodes, a dilute acid solution called electrolyte, and a nonconducting container called the cell. In a glass container filled with sulphuric acid there are two plates: one copper and are connected by a copper wire, electricity will flow through it from the copper plate to the zinc plate.
For the voltaic cell the copper plate is the positive electrode and the zinc plate the negative electrode a copper wire will convey electricity and is called an electrical conductor. Copper, aluminium and silver are good conductors. They must be surrounded by protective material which does not conduct electricity. Such materials are called electrical insulators (glass, wood, rubber, some plastics, insulation tape)
Remember that faulty insulation is dangerous and leads to unwanted electrical flow and probably to local overheating.
Words to the text
1. Source-источник
2. Cell-элемент
3. Flashlight-сигнальный огонь
4. Plate-пластинка
5. Acid-кислота
6. Copper-медь
7. Wire-проволока, провод
8. Insulator-изолятор
9. Rubber-резина, каучук
10. Tape-лента, тесьма
11. To use-использовать
12. To compose-составлять
13. To fill-наполнять
14. To connect-соединять
15. To flow-течь
16. To convey-переправлять
17. To surround-окружать
18. To remember-помнить
19. Common-общий, частый
20. Portable-переносной
21. Dry-сухой
22. Wet-мокрый
23. Dissimilar-несходный
24. Sulphuric-серный
25. Faulty-неисправный
26. Dangerous-опасный
Вставьте пропущенные слова
1. A battery is a source of ….
2. Battery cells are manufactured in ….
3. The voltaic cell is composed of ….
4. Cells connected together form ….
5. The positive electrode is ….
6. The negative electrode is ….
7. Series connection means ….
8. Materials which do not conduct electricity are called ….
Electrical, insulators, two common forms, electrical energy, copper plate, Zink plate, three parts, battery, the terminal of one cell is connected to
Answer the questions
1. What does an ammeter measure?
2. Was Andre m. ampere a French or Italian scientist?
3. How is the current in a conductor determined?
4. What is the unit called by which resistance is measured?
5. Does a wattmeter measure electrical power?
6. How does an ammeter measure electric current?
The capacitor
A capacitor is an electrical device for storing quantities of electricity. The general form of a capacitor is what of two parallel conducting plates.
Such plates are of relatively large area, close together, and contain between them a non-conducting medium called the dielectric common dielectric are air, glass, oil and waxed paper.
To increase the capacitance of a capacitor the following changes can be made: first, the area of the plates may be increased.
Second, the plates may be put closer together
Third, a more suitable dielectric may be inserted between the plates.
If the plates of a capacitor are small in area and far apart, the capacitance is small. If the area is large and plates close together, the capacitance is large. The unit of capacitance, the farad, named in honour of Michael Faraday scientist a capacitance of 1 farad is very large and for practical purposes is not used. The microfarad is more convenient. Capacitors in common use today are of various kinds, sizes and shapes. Perhaps the most common is the so-called «paper capacitor» used in radios and the ignition system of automobiles another type of capacitor is the variable capacitor commonly used in tuning radios.
Word to the text
1.
2. Capacitor-конденсатор
3. Capacitance-ёмкость;ёмкостное сопротивление
4. Device-прибор;устройство
5. Quantity-количество
6. Plate-пластина
7. Air-воздух
8. Glass-стекло
9. Waxed paper-пропитанная воском бумага
10. Area-площадь
11. Purpose-цель
12. To store-накапливать
13. To change-менять
14. To contain-содержать
15. To increase-увеличивать
16. To insert-вставлять
17. To be used-быть использованным
18. To be called-быть названным
19. General-обычный, основной
20. Common-общий
21. Suitable-подходящий
22. Convenient-удобный
23. Various-различный
24. Variable-изменчивый
25. Relative-относительный
Power Transmission
A transformer is an electrical device by which the electromotive force of a source of alternating current may be increased or decreased. They are widespread in long distance power transmitters and receivers, television. Nearly all transformers come under one of the two following classes: step-up and step-down transformers. In the transmissions of electrical energy over wires for long distance, transformers are practically indispensable.
At the power house in the distant mountains, electric current is generated by huge alternating generator at the low voltage of several thousand volts. If an attempt was made to transmit this electrical energy, at a voltage of 2,200 volts, over many miles to a distant city, the current would be so large that nearly of the energy would be consumed in heating the power line. To avoid large heat losses, transformers at the power house step the voltage up to some 220000 volts before switching the current onto the power line.
At the city end of the power line, a transformer substation steps the voltage down to its original value of 2200 volts. From there branch lines distribute the power to various section of the city where smaller transformers step it down again to the relatively safe voltage of 110 to 220 volts.
Words to the text
1. A transformer-трансформер
2. A source-источник
3. A force-сила
4. A wire-провод
5. Voltage-электрическое напряжение
6. Ar attempt-попытка
7. Losses-потери
8. Substation-подстанция
9. Branch-отрасль
10. Line-линия
11. To increase-увеличить
12. To decrease-уменьшить
13. To step up-повышать напряжение
14. To step down-понижать напряжение
15. To generate-производить
16. To make-делать
17. To consume-расходовать
18. To avoid-избегать
19. To switch-включать
20. To distribute-распределять
21. Alternating-переменный
22. Widespread-широко распространенный
23. Following-следующий
24. Indispensable-совершенно необходимый
25. Distant-далекий
26. Huge-огромный
27. Various-различный
28. Relative-относительный
Сгруппируйте синонимы
To step up; part; to step down; to increase; to decrease; not far; too; as; since; as well as; section; different; near; various; huge; end; finish; great.
Контрольная работа
Вариант № 1
Задание 1. Вставить подходящее по смыслу слово.
1. At present the nature of …is explained by the electron theory.
a) electrification
b) history
c) town
2) Any instrument which measures electrical values is called … .
a) atom
b) a meter
c) a battery
3) An Italian … Volta made many experiments with electricity.
a) musician
b) driver
c) scientist
Задание 2. Найдите русские эквиваленты.
1) sources of electrical energy
2) a capacitor is an electrical device
3) alternating current
4) positive electrode
5) measuring units and instruments
6) the ignition system of automobiles
Задание 3. Вставить правильную форму глагола.
1) The mechanic (is repairing / was repairing) the engine now.
2) He (measured, will measure) electrical power 2 hours ago.
3) A new power station (is built / will be built) in the nearest future.
4) Now all substances (is, are) good conductors of electricity.
5) Battery cells (have, has) dry cells and wet cells.
Задание 4. Сгруппировать синонимы
Different, not far, end, great, near, finish, various, huge, step up, increase, section, part, step down, decrease.
Задание 5. Найдите английские эквиваленты.
Электрический ток, проводник, вольтметр, сопротивление, медный провод, конденсатор, передача энергии, генератор.
Контрольная работа
Вариант № 2
Задание 1. Вставить подходящее по смыслу слово.
2. A capacitor is used for storing … .
a) petrol
b) electricity
c) meter
2) He … the electric motor and the first telegraph.
a) invented
b) printed
c) called
Задание 2. Найдите русские эквиваленты.
1) electrical current
2) electron theory
3) connected between the plates
4) conduct electricity
5) a container for storing electricity
6) transmission of electrical energy
Задание 3. Вставить правильную форму глагола.
1) The principles of the capacitor (are illustrated, was illustrated)
2) Faraday (carried out, will carry out) series of experiments in 1831.
3) The scientist Volta (faces, faced) the problem how electricity could be produced.
4) Some new instruments (will be made, are made) next month.
5) Newton (have expressed, has expressed) the connection between force and motion.
Задание 4. Сгруппировать антонимы .
Noise, positive, start, silence, far, finish, theory, negative, near, practice, famous, unknown, rest, motion.
Задание 5. Найдите английские эквиваленты.
Положительный электрод, источник электрической энергии, проводник, проводить опыты, батарея, прибор, электрический ток, изолятор.
The Concept of Electrical Current
In the beginning of the 17th century Sir William Gilbert discovered that many substances could be electrified by friction. Gilbert named this effect «electric» after the world «electron» - the Greek name for amber. In 1756 the great Russian scientist M. V. Lomonosov was the first to make theoretical analysis of electrical phenomena.
At present the nature of electrification is explanted by the electron theory. According to the modern theory all matter is composed of atoms or tiny particles. There are many kinds of atoms. Each atom consists of a nucleus, a small positively charged mass and a number of lighter negatively charged particles called electrons, which revolve around the nucleus. Normally each atom of a substance is electrically neutral, or it has equal amounts of negative and positive charges, i.e. produces no electrical effects. If the number of negative charges is not equal to the number of positive charges, the matter will produce electrical effects.
When an electric charge is at rest it is spoken of as static electricity, but when it is in motion it is referred to as an electric current. In most cases, an electric current is described as a flow of electric charges along a conductor.
Not all substances are good conductors of electricity, as a general rule metals are good conductors of electricity, whereas nonmetals are poor conductors. The poorest of conductors are commonly called insulators or nonconductors. There are a large number of substances that are neither good conductors of electricity nor good insulators. These substances are called semi-conductors. An electric current which flows in the same direction through a conductor or a current which does not change its polarity is called a direct current or a continuous current. Its abbreviation is D. C. An alternating current (A. C.) flows first in one direction and then in the other.
An electric circuit is a path through which an electric current flows. This is a complete path along which electrons can transmit their charges. An electric circuit includes a battery, generator, or magnetic means for producting current flow. Some portion of the circuit is made to do useful work.
The circuit is said to be open when no charges can move due to a break in the path. The circuit is said to be closed when no break exists-when switches are closed and all connections are properly made.
Special symbols are used to show electrical systems. There is a wide range of these symbols. There are some of them which are used when we draw circuits. And now look at the diagram of series and parallel arrangements.
Words to the text
1) insulator-изолятор
2) substance-вещество, материя
3) friction-трение, сцепление
4) nucleus-ядро, ячейка
5) amount-сумма, количество
6) charge-заряд, загрузка
7) rest-покой, отдых
8) motion-движение
9) flow-поток, течение
10) circuit-цепь, кругооборот
11) current-течение, ток
12) path-путь, дорожка, линия
13) break-прорыв, интервал, перелом
14) To discover-открывать
15) To make-делать
16) To explain-объяснять
17) To consist-состоять из
18) To revolve-вращаться
19) To produce-производить
20) To transmit-передавать
21) To include-включать
22) To exist-существовать
23) To use-использовать
24) Tiny-маленький, крошечный
25) Light-легкий, светлый
26) Equal-равный
27) Poor-бедный, слабый
28) Continuous-непрерывный, постоянный
29) Wide-широкий
30) Alternating-переменный
Найдите в тексте
а) интернационализмы б) ложные друзья переводчика
Дайте краткие определения следующих понятий:
Static electricity
Electric current
Direct current
Alternating current
Electric circuit
An open circuit
A closed circuit
An electrical phenomenon
An electron theory
Positive charges
Negative charges
Conductors of electricity
Special symbols
Дата: 2019-03-05, просмотров: 1017.