The invention of the voltaic cell in 1800 gave electrical experimenters a source of a constant flow of current. Seven years later the Danish scientist and experimenter, Oersted, decided to establish the relation between a flow of current and a magnetic needle. It took him at least 13 years more to find out that a compass needle is deflected when brought near a wire through which the electric current flows. At last, during a lecture he adjusted, by chance, the wire parallel to the needle. Then, both he and his class saw that when the current was turned on, the needle deflected almost at right angles towards the conductor. As soon as the direction of the current was reversed, the direction the needle pointed in was reversed too. Oersted also pointed out that if the wire were adjusted below the needle, the deflection was reversed.
The above-mentioned phenomenon highly interested Ampere who repeated the experiment and added a number of valuable observations and statements. He began his research under the influence of Oersted's discovery and carried it on throughout the rest of his life.
Everyone knows the rule thanks to which we can always find the direction of the magnetic effect of the current. It is known as Ampere's rule. Ampere established and proved that magnetic effects could be produced without any magnets by means of electricity alone. He turned his attention to the behaviour of the electric current in a single straight conductor and in a conductor that is formed into a coil, i.e. a solenoid.
When a wire conducting a current is formed into a coil of several turns, the amount of magnetism is greatly increased.
It is not difficult to understand that the greater the number of turns of wire, the greater is the m.m.f. (that is the magnetomotive force) produced within the coil by any constant amount of current flowing through it. In addition, when doubling the current, we double the magnetism generated in the coil.
A solenoid has two poles which attract and repel the poles of other magnets. While suspended, it takes up a north and a south direction exactly like the compass needle. A coreof iron becomes strongly magnetized if placed within the solenoid while the current is flowing.
When winding a coil of wire on an iron core, we obtain an electromagnet. That the electromagnet is a controllable and reliable magnet is perhaps known to everyone. It is, so to say, a temporary magnet provided by electricity. Its behaviour is very simple. The device is lifeless unless an electric current flows through the coil. However, the device comes to life if the current flows. The iron core will act as a magnet as long as the current continues to pass along the winding.
I. Learn the following words, groups of words. Translate the sentences.
1. to add — прибавлять, складывать. When we add heat temperature rises.
2. at right angles — под прямым углом. The magnetic and the electrical fields act at right angles to each other.
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3. to adjust — регулировать; устанавливать. We must adjust the voltage before our experiment. The student adjusted a thermometer above a heated body.
4. as soon as — как только. The current will flow as soon as you close the circuit.
5. coil — катушка. Let us pass the current through the coil.
6. constant — постоянный. The temperature of boiling water does not change at constant pressure.
7. core — сердечник. The core of the electromagnet is usually made of iron.
8. to establish — устанавливать, основывать. Who established the relation between current and resistance?
9. to find out — выяснять; понимать. Who found out the relation between electricity and magnetism?
10. needle — стрелка. The compass needle always points to the North.
11. to reverse — изменять на обратное, реверсировать. If the resistance is reversed the current in the circuit is reversed too.
12. to repel — отталкивать. Like poles of the magnet repel each other.
13. rule — правило. Why did you not learn grammar rules?
14. straight — прямой. This article deals with a straight conductor carrying a current.
15. turn — виток. The coil may contain several turns of wire.
16. to turn on — включать. In the evening I turn the TV on.
II.Learn to recognize the following international words.
magnetic, compass, parallel, effect, magnet, magnetism, solenoid, electromagnet, process, electricity
III. Translate the following groups of words.
to adjust the instrument, constant temperature, coil of wire, iron core, to reverse the direction, principal rule
стальная стрелка, прямой проводник, как только, под прямым углом, изменять направление, установить разницу
IV. Translate the following sentences and define the functions of the word that.
1. It is clear that the greater the number of free electrons in a substance, the better that substance conducts the electric current. 2. An electric current passing through a wire heats that wire. 3. It is the unit of current that is named after Ampere. 4. That a solenoid has two poles that attract and repel the poles of other magnets is a well-known fact. 5. The physics of bodies at rest is much simpler than that of the bodies that are in motion. 6. There was a time when lightning was a problem that scientists tried to solve but at present everybody knows that it is an electric spark like that produced by the electric machines. 7. Experiments show that all gases expand when heated.
V. Fill in the blanks with suitable words given below:
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where, which, when, who, that
1. We know... Oersted established the relation between the flow of electric current and a magnetic needle. 2. The great scientists Volta, Ampere and P. N. Yablochkov may be named among those... have greatly contributed to electrical engineering. 3. The end... the lines of force leave the coil after passing through its core will act like a north magnetic pole. 4.... there is a certain connection between electricity and magnetism was proved by experiments. 5.... he placed the wire parallel to the needle he saw... the needle deflected. 6. A wire... is wound in the form of a solenoid acts like a magnet as long as it is carrying a current.
VI. Translate the following sentences paying attention to the words in bold type.
a) 1. Ampere's contribution to electrodynamics as hecalled the new science began in 1820. 2. As it is impossible to detect electricity by our physical senses, we generally detect it by its effects. 3. An electromagnet loses its magnetic properties as soon as the current is turned off. 4. In certain branches of industry, chemical energy is not so widely used as mechanical energy. 5. The average speed of all molecules remains the same as long as the temperature is constant. 6. In order to produce electricity more economically the generators must be as large as possible. 7. As a gas is cooled, it loses heat as well as energy. 8. The magnetic effect of an electric current is the subject of the present article, as for the heating effect it was dealt with before.
b) 1. Rubber is a very poor conductor of electricity. 2. This is the very appliance which I need for my experiment. 3. M. V. Lomonosov was born in the family of a poor peasant. 4. All metals are poor insulators of electric current. 5. Electricity at rest or in a static condition does no work. 6. Heat causes many chemical reactions. 7. What causes the electrons to flow along the wire? 8. A short circuit may be the cause of fire.
VII. Give suitable prepositions to the following verbs and form sentences with them.
to equip, to depend, to compare, to consist, to contribute, to be interested, to be familiar, to point, to look, to start, to speak
VIII. Answer the following questions.
1. When was the voltaic cell invented? 2. What did Oersted decide to establish? 3. What did he find out? 4. When did the needle deflect? 5. Who repeated Oersted's experiments? 6. Do you know Ampere's rule? 7. What did Ampere establish and prove? 8. When is magnetism greatly increased? 9. Is the magnetic effect produced when the charges are at rest? 10. What is an electromagnet? 11. When does the iron core act as a magnet?
IX. Compare:
1. Potential energy and kinetic energy. 2. A series circuit and a parallel circuit. 3. A conductor and an insulator. 4. The magnetic effect of an electric current and the heating effect of an electric current.
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X. Make up the annotation of the text and retell it.
LESSON EIGHTEEN
Read and translate the text.
GENERATORS
The dynamo invented by Faraday in 1831 is certainly a primitive apparatus compared with the powerful, highly efficient generators and alternators that are in use today. Nevertheless, these machines operate on the same principle as the one invented by the great English scientist. When asked what use his new invention had, Faraday asked in his turn: "What is the use of a new-born child?" As a matter of fact, "the new-born child" soon became an irreplaceable device we cannot do without.
Although used to operate certain devices requiring small currents for their operation, batteries and cells are unlikely to supply light, heat and power on a large scale. Indeed, we need electricity to light up millions of lamps, to run trains, to lift things, and to drive the machines. Batteries could not supply electricity enough to do all this work.
That dynamo-electric machines are used for this purpose is a well-known fact. These are the machines by means of which mechanical energy is turned directly into electrical energy with a loss of only a few per cent. It is calculated that they produce more than 99, 99 per cent of all the world’s electric power.
There are two types of dynamos, namely, the generator and the alternator. The former supplies d.c. which is similar to the current from a battery and the latter as its name implies provides a.с.
To generate electricity both of them must be continuously provided with energy from some outside source of mechanical energy such as steam engines, steam turbines or water turbines, for example.
Both generators and alternators consist of the following principal parts: an armature and an electromagnet. The electromagnet of a d.c. generator is usually called a stator for it is in a static condition while the armature (the rotor) is rotating. An elementary d.c. generator consists of the armature, the electromagnet, the shunt winding, the commutator and the load. Alternators may be divided into two types: 1. alternators that have a stationary armature and a rotating electromagnet; 2. alternator whose armature serves as a rotor but this is seldom done. In order to get a strong e.m.f., the rotors in large machines rotate at a speed of thousands of revolutions per minute (r.p.m.). The faster they rotate, the greater the output voltage the machine will produce.
In order to produce electricity under the most economical conditions, the generators must be as large as possible. In addition to it, they should be kept as fully loaded as possible all the time. It is interesting to note here that the biggest generators ever installed at any hydroelectric station in the world are those installed in Russia: the Bratskaya hydroelectric station is equipped with 225,000 kilowatt (kW) generators. Russian scientists constructed more powerful generators which are installed at the Krasnoyarskaya station. Our industry produces even greater power installations of 1,200 MW for the steam power plants which play such an important part in the electrification of our country.
Exercises
I. Learn the following words, groups of words. Translate the sentences.
1. armature —якорь. The armature is a part of a generator.
2. to calculate — рассчитывать, вычислять. If you know Ohm's law you can calculate the circuit.
3. compared with — по сравнению с. A ton of uranium can give much more energy compared with a ton of coal.
4. to equip — оборудовать. Our laboratory is equipped with reliable instruments.
5. to install — устанавливать, монтировать. A new powerful generator was installed at the power plant.
6. to operate — работать, действовать. A transformer operates on the principle of electromagnetic induction.
7. rated capacity — номинальная мощность. This power plant has reached its rated capacity.
8. revolutions per minute — оборотов в минуту. How many revolutions per minute does this steam turbine make?
9. to rotate — вращать(ся). Water rotates the turbines at the hydropower stations.
10. scale — масштаб; шкала. Measuring instruments are produced on a large scale in Russia. The Centigrade scale is not used in Great Britain.
11. speed — скорость. Gas turbines rotate with great speed.
12. stationary — неподвижный, стационарный. No current is generated while the magnet is stationary.
13. the former — первый из упомянутых; the latter — последний из упомянутых. There are two kinds of current: a.с. and d. с. The former changes its direction, the latter does not.
14. steam power plant — тепловая электростанция. Steam power plants operate on gas and coal.
15. winding — обмотка. Faraday's coil consisted of eight windings of copper wire.
II. Learn to recognize the following international words.
solenoid, shunt, electrification, dynamo, primitive, rotor, kilowatt, electromagnet, apparatus, industry, plan, elementary
III. Translate the following groups of words.
compared with the results, to install the turbine, to equip with reliable installations, stationary equipment, rotor windings, 5,000 revolutions per minute
увеличивать скорость, номинальная мощность мотора, тепловая электростанция, первый из упомянутых, последний из упомянутых, в большом масштабе
IV. Read the following abbreviations and give their full forms.
i.e., a.c., d.c., r.p.m., e.m.f., m.m.f., 317°F, 45°C, etc.
V.Translate the following sentences.
1. There is a great number of engineering problems the Russian scientists work at. 2. It is quite impossible to name a scientific problem M.V. Lomonosov did not turn his attention to. 3. There are many electric appliances we cannot do without. 4. The experiment I told you about will take much time. 5. The direction the needle points in changed several times. 6. The speed a given molecule travels with is greatly increased when a gas is heated.
VI. Form adjectives using the suffixes -able, -full, -less, -ous.
control, continue, danger, value, replace, need, power, peace, use, life, change, desire, vary
VII. Form adverbs using the suffix -ly and translate them.
exact, electrical, general, gradual, negative, natural, opposite, previous, usual, easy, hard, late
VIII. Translate the following sentences paying attention to the construction the former... the latter.
1. There are two kinds of current: a.с. and d.c. The former changes its direction, the latter does not. 2. I have two friends, Nick and Pete. The former studies at the university, the latter works at the factory. 3. He has a book on electrical engineering and a book on nuclear physics. The former is in Russian and the latter is in English. 4. I spoke to professors G. and W. The former delivers lectures on chemistry, the latter on semiconductors.
IX. Answer the following questions.
1. When did Faraday invent the dynamo? 2. Was Faraday an American scientist? 3. Can batteries supply power on a large scale? 4. What do we need electricity for? 5. What are dynamo electric machines used for? 6. What types of dynamos do you know? 7. What are the principal parts of a generator? 8. In what condition is the stator of an electromagnet? 9. What generators is the Bratsk hydroelectric station equipped with? 10. What is their rated capacity? 11. What are the largest steam power plants in Europe?
X. Ask your group-mate the following questions. Let him/her answer them.
1. if batteries can supply light, heat and power on a large scale. 2. if the electromagnet is a temporary magnet provided by electricity. 3. if the electromagnet is lifeless unless the electric current flows through the coil. 4. if the iron core will act as a magnet as long as the current continues to pass along the winding. 5. if the alternator provides a.с. 6. if the generator must be turned by some outside source of mechanical energy.
XI. Make up the annotation of the text and retell it.
LESSON NINETEEN
Read and translate the text
POWER TRANSMISSION
They say that about a hundred years ago, power was never carried far away from its source. Later on the range of transmission was expanded to a few miles. And now, in a comparatively short period of time, electrical engineering has achieved so much that it is quite possible, at will, to convert mechanical energy into electrical energy and transmit the latter over hundreds of kilometers and more in any direction required. Then in a suitable locality the electric energy can be reconverted into mechanical energy whenever it is desirable. It is not difficult to understand that the above process has been made possible owing to generators, transformers and motors as well as to other necessary electrical equipment. In this connection one cannot mention the growth of electric power generation in this country. The longest transmission line in pre-Revolutionary Russia was that connecting the Klasson power station with Moscow. It is said to have been 70 km long, while the present Volgograd—Moscow high-tension (the English terms "high-tension" and "high-voltage" are interchangeable) transmission line is over 1,000 kilometers long. Generally speaking, the length of high-tension transmission lines in Russia is so great that they could circle the globe six times, if not more.
It goes without saying that as soon as the electric energy is produced at the power station, it is to be transmitted over wires to the substation and then to the consumer. However, the longer the wire, the greater is its resistance to current flow. On the other hand, the higher the offered resistance, the greater are the heating losses in electric wires. One can reduce these undesirable losses in two ways, namely, one can reduce either the resistance or the current. It is easy for us to see how we can reduce resistance: it is necessary to make use of a better conducting material and as thick wires as possible. However, such wires are calculated to require too much material and, hence, they will be too expensive. Can the current be reduced? Yes, it is quite possible to reduce the current in the transmission system by employing transformers. In effect, the waste of useful energy has been greatly decreased due to high-voltage lines. It is well known that high voltage means low current, low current in its turn results in reduced heating losses in electrical wires. It is dangerous, however, to use power at very high voltages for anything but transmission and distribution. For that reason, the voltage is always reduced again before the power is made use of.
Lasers. Russian scientists are successfully developing quantum generators, called lasers, for emitting light amplitude radio waves. Theoretical calculations have shown that lasers are very likely to transform the energy of light radio waves into electrical energy with an efficiency amounting to about 100 per cent. It means that electrical power might be transmitted over considerable distances with negligible losses and what is very important without the use of transmission lines.
Exercises
I. Learn the following words, groups of words. Translate the sentences.
1. to amount to — доходить до. The electric power generation in Russia amounted to a great figure.
2. at will — по желанию. The temperature in this room can be regulated at will.
3. considerable — значительный. We pay considerable attention lo the construction of steam power stations.
4. distribution — распределение. Power distribution is indicated by a straight line in this figure.
5. to emit — излучать, выделять, испускать. A hot body emits heat.
6. equipment — оборудование. This equipment is reliable in operation.
7. expensive — дорогой. Nuclear fuel is more expensive than mineral fuel.
8. growth — рост, увеличение. The growth of cities requires the increase of power generation.
9. range — диапазон. This measuring instrument has a wide temperature range.
10. to reduce — понижать, уменьшать. High voltage is usually reduced at distribution substations.
11. to result in — приводить к; заканчиваться. The scientist's work resulted in a great discovery.
12. successfully — успешно. Our industry successfully develops powerful reactors.
13. transmission — передача. Underground cables are used for power transmission in large cities.
14. tension — напряжение. High-tension transmission lines cross our country from East to West.
15. wave — волна. A.S. Popov experimented with electromagnetic waves.
II. Translate the following groups of words.
considerable success, to emit electrons, load distribution, to reduce power losses, to result in great achievements, growth of population, straight line
дорогое оборудование, передача электроэнергии, значительное расстояние, излучать тепло, распределение времени
III. Give all the meanings of the following words consulting a dictionary:
scale, generation, armature, revolution, commutator, amplitude, iron, needle, second
IV. Complete the following sentences.
1. Owing to the transformer it became possible.... 2. It was Ampere who.... 3. The dynamo-electric machines are used for.... 4. In order to reduce resistance in a wire, it is necessary.... 5. The waste of useful energy can be decreased …. 6. Coal is burned in order to.... 7. Lasers are used for....
V. Translate the following sentences.
1. Чем сильнее магнитное поле, тем больше ток. 2. Чем больше ток, текущий по проводнику, тем выше температура проводника. 3. Чем меньше труба, тем меньше воды проходит через нее. 4. Чем больше скорость движения между магнитным полем и проводниками, тем больше ток. 5. Чем короче проводник, тем меньше сопротивление проходящему току.
VI. For the terms given in (a) find the Russian equivalents in (b).
a) 1. power plant; 2. power supply; 3. power generation; 4. power source; 5. power transmission; 6. power unit; 7. power installation; 8. power substation; 9. power transformer; 10. power factor; 11. power engineering; 12. power capacity; 13. power distribution; 14. power loss
b) 1. выработка электроэнергии; 2. потеря энергии;
3. электроподстанция; 4. силовой трансформатор; 5. коэффициент мощности; 6. производительность; 7. источник энергии; 8. распределение энергии; 9. электростанция; 10. передача электроэнергии; 11. силовая установка; 12. источник питания; 13. энергетика; 14. энергоблок
VII. a) Choose the right term; b) explain the statements.
1. The coil of wire that rotates in a dynamo or a motor is known as:
a) a turbine, b) a stator, c) an armature, d) a generator.
2. Running water is an illustration of: a) potential energy, b) kinetic energy, c) electric energy, d) heat energy.
3. Steam generators produce electrical energy from: a) potential energy, b) chemical energy, c) light energy, d) mechanical energy.
VIII.Answer the following questions.
1. What made it possible to transmit electric energy over hundreds of kilometers? 2. Can electric energy be reconverted into mechanical energy? 3. What are transformers used for? 4. What do you know about the longest transmission line in pre-revolutionary Russia? 5. How long is the Volgograd—Moscow high-tension transmission line? 6. In what way can the heating losses be reduced in transmission lines? 7. How can resistance be reduced in electric wires? 8. Why are high-voltage lines used for power transmission? 9. Is it possible to use quantum generators for power transmission? 10. What have theoretical calculations shown?
IX. Make up the annotation of the text and retell it.
LESSON TWENTY
Read and translate the text
TRANSFORMERS
The transformer is a device for changing the electric current from one voltage to another. As a matter of fact, it is used for increasing or decreasing voltage. A simple transformer is a kind of induction coil. It is well known that in its usual form it has no moving parts. On the whole, it requires very little maintenance if it is not misused and is not damaged by lightning.
We may say that the principal parts of a transformer are two windings, that is coils, and an iron core. They call the coil which is supplied with current the "primary winding", or just "primary" for short. The winding from which they take the current is referred to as the "secondary winding" or "secondary" for short. It is not new to you that the former is connected to the source of supply, the latter being connected to the load.
When the number of turns of wire on the secondary is the same as the number on the primary, the secondary voltage is the same as the primary, and we get what is called a "one-to-one" transformer. In case, however, the number of turns on the secondary winding is greater than those on the primary, the output voltage is larger than the input voltage and the transformer is called a step-up transformer. On the other hand, the secondary turns being fewer in number than the primary, the transformer is known as a step-down transformer.
The transformer operates equally well to increase the voltage and to reduce it. By the way, the above process needs a negligible quantity of power. It is important to point out that the device under consideration will not work on d.c. but it is rather often employed in direct-current circuits.
The transformers are used in stepping up the voltages for distribution or transmission over long distances and then in stepping these voltages down. For example, three large step-up transformers are used to increase the potential to 275,000 volts for transmission over long-distance transmission lines. At the consumer's end of the line, in some distant locality, three step-down transformers are made use of to reduce that value (i.e., 275,000 volts) to 2,300 volts. Local transformers, in their turn, are expected to decrease the 2,300 volts to lower voltages, suitable for use with small motors and lamps. One could have some other transformers in the systems that reduce the voltage even further. All radio sets and all television sets are known to use two or more kinds of transformers. These are familiar examples showing that electronic equipment cannot do without transformers. The facts you have been given above illustrate the wide use of transformers and their great importance.
Exercises
I. Learn the following words, groups of words. Translate the sentences.
1. consumer — потребитель. Power transmission system connects the power station to the consumer.
2. to damage — разрушать, повреждать. The nearest power station was damaged.
3. induction coil — индукционная катушка. Theinduction coil is connected to the circuit in order to increase its inductance.
4. input — вход; подводимая мощность; входной. The input power of this substation is limited.
5. local — местный. The voltage is reduced at local substations.
6. maintenance — техническое обслуживание, уход. The maintenance of this new equipment is expensive.
7. number — число; номер. The number of nuclear power plants has increased in this country. What is the number of your telephone?
8. output — выходная мощность; выходной. The scientists try to increase the output power of the generators.
9. to point out — указывать. The achievements of Russia in power engineering were pointed out in my report.
10. primary — первичный; первичная обмотка трансформатора; secondary — вторичный, вторичная обмотка трансформатора. A simple transformer has aprimary and a secondary winding.
11. source of supply — источник питания. A battery is a source of supply.
12. to step down — понижать. What device is used to step down the voltage?
13. to step up — повышать. A transformer is used to step up and down the voltage.
14. value — величина. Let us compare these two given values.
15. whole — целый, весь. The students have translated thewhole article.
II. Learn to recognize the following international words.
globe, laser, quantum, theoretical, induction, electronic, plastics, asbestos, volt
III. Translate the following groups of words.
to damage by lightning, secondary distribution line, the number of windings, to step up the current, source ofsupply, the whole world
индукционная катушка, число потребителей, понижать напряжение, вся страна, местные фабрики, первичная обмотка
IV. Form as many words as possible using suffixes and prefixes. Define the parts of speech of the new words and translate them.
engine, apply, differ, electric, value, oppose, transform, magnet, conduct, neglect
V.Translate the following sentences.
1. Говорят, что этот прибор описан в предыдущей статье. 2. Считали, что ток течет от положительного потенциала к отрицательному. 3. Говорят, что мой друг — хороший математик. 4. Известно, что М.В. Ломоносов основал Московский университет. 5. Кажется, что это вещество имеет некоторые другие свойства. 6. Известно, что переменный ток меняет свое направление.
VI. Form nouns from thefollowing words using suitable suffixes.
construct, develop, consider, distribute, deflect, equip, connect, require, produce, state, suit
VII.For the word combinations given in (a) find the Russian equivalents in (b).
a) 1. a number of; 2. as a matter of fact; 3. on the basis of; 4. for this reason; 5. it goes without saying; 6. at last; 7. on the whole; 8. to step up; 9. to increase current; 10. to offer resistance; 11. electrical engineering; 12. to step down
b) 1. наконец; 2. повышать (напряжение); 3. оказывать сопротивление; 4. понижать (напряжение); 5. ряд; 6. увеличить ток; 7. на основе чего-л.; 8. по этой причине; 9. в целом; 10. электротехника; 11. на самом деле; 12. само собой разумеется
VIII. Translate the following sentences and define the functions of the word but.
1. The Fahrenheit scale is mainly used in English speaking countries but it is not used in Russia. 2. His scientific activity lasted but twenty years, but in these twenty years he did very much. 3. Motors are widely employed not only in industry but also in everyday life. 4. There is but one measuring scale in the instrument. 5. Everyone took an examination in physics but Novikov. 6. A simple transformer is but a kind of induction coil.
IX. Arrange the following words in the pairs of synonyms.
a) 1. amount; 2. big; 3. matter; 4. application; 5. at present; 6. tube; 7. research; 8. to step down; 9. appliance; 10. minute; 11. arrow
b) 1. investigation; 2. device; 3. needle; 4. quantity; 5. substance; 6. to lower; 7. small; 8. large; 9. new; 10. use; 11. pipe
X.Arrange the following words in the pairs of antonyms.
a) 1. left; 2. increase; 3. beginning; 4. d.c.; 5. above; 6. step-up; 7. at rest; 8. high; 9. short; 10. more
b) 1. end; 2. low; 3. long; 4. step-down; 5. in motion; 6. less; 7. decrease; 8. below; 9. a.c.; 10. right
XI.Answer the following questions.
1. What is a transformer? 2. What is a transformer used for? 3. Are there any moving parts in a transformer? 4. Can a transformer be damaged by lightning? 5. What are the principal parts of a transformer? 6. How many windings are there in a transformer? 7. What winding is connected to a load? 8. What is the purpose of a step-up transformer? 9. What is known as a step-down transformer? 10. Does a transformer work on d.c.? 11. In what circuits is the transformer used? 12. For what purpose are step-down transformers used? 13. Is your radio set equipped with a transformer? 14. Can we do without transformers? 15. Are transformers used both in industry and in our homes?
XII. Compare:
1. A solenoid and an electromagnet. 2. A direct current and an alternating current. 3. A step-up transformer and a step-down transformer. 4. A stator and a rotor. 5. A primary winding and a secondary winding.
XIII. Make up the annotation of the text and retell it.
ЧЕЛЯБИНСКИЙ ГОСУДАРСТВЕННЫЙ АГРОИНЖЕНЕРНЫЙ УНИВЕРСИТЕТ
МЕТОДИЧЕСКИЕ УКАЗАНИЯ
по английскому языку
для развития навыков работы со спецтекстами
для студентов I и II курсов
по специальностям ЭАСХП и Электроснабжение
Челябинск
Составитель Халупо О.И.