Electric current and mankind

УЧЕБНО-МЕТОДИЧЕСКОЕ ПОСОБИЕ

ЭНЕРГИЯ

ДЛЯ СТУДЕНТОВ ОЧНОЙ ФОРМЫ ОБУЧЕНИЯ

ЭЛЕКТРОЭНЕРГЕТИЧЕСКОГО ФАКУЛЬТЕТА ВОЛГАУ

Храмова Оксана Владимировна

Ст. Преподаватель

Кафедра «Иностранные языки»

Факультет «Сервис и туризм»

ФГБОУ ВПО Волгоградский ГАУ
LESSON 1

ELECTRIC CURRENT AND MANKIND

The electric currentwas born in the year 1800 when Volta constructed the first source of continuous current. Since that time numerous scientists and inventors, Russian and foreign, have greatly contributed to its further development and practical application.

As a result, one cannot imagine modern civilization without the electric current. We can't imagine how people could do withoutthe electric lamp, without vacuum cleaners, refrig­erators, washing machines and other electrically operated devicesthat are widely used today. In fact, telephones, lifts, electric trams and trains, radio and television, mobile phone and computer have been made possible only owing to the electric current.

Elec­tric power finds its most important use in industry.  The electric motor transformselectric power into mechanical power. It finds a wide application at every industrial enterprise.

 

Exercises

Learn the following active words and use them in the sentences of your own

 

apply (v)                 применять, использовать

application (n)          применение

current (n)            ток

device (n)                  прибор, устройство

develop (v)           разрабатывать, развивать(ся)

electricity (n)           электричество

industrial (a)           промышленный

invent (v)                  изобретать

measure (v)           измерять

serve (v)                   служить, обслуживать

scientist (n)           ученый                

 

2. Translate the following chains of words into Russian, define what part of speech they are:

Science – scientist – scientific-scientifically; develop – developer - developing - development, invent - inventor - invention; measure- measuring- measurement; apply – application - applicable— appliance; use – user – useful - useless - usage; transform - transformer - transformation; electric- electricity – electrical - electrically; serve - server-service - servant.

Speak on:

1. The use of the electric current in industry.

2. The use of the electric current in our everyday life.

13. What do you call a device which:

1. measures the temperature of hot melted metals.

2. transforms electric power into mechanical power.

3. lifts objects weighing thousands of tons.

4. lights your room.

Enumerate your home appliances using electric power

Put six general questions to the text.

Make an outline of the text.

Retell the text.

LESSON TWO

KINDS OF POWER

Scientifically speaking, power is the ability to do work. There are various forms of power, such as: heat, mechanical, electrical, chemical, atomic and so on. One might also mention the two kinds of mechanical power—potential and kinetic, potential power being power of position while kinetic power is power of motion. It is well known that one form of power can be changed into another.

Take a waterfall as an example. Water falling from its raised position, power changes from potential to kinetic. If there is a hydroelectric plant at the waterfall, the power of the falling water is used to drive the turbines. The tur­bines, driven by the kinetic power of the running water, turn electric generators, these generators producing electric power. Thus, the mechanic power of falling water is turned into electric power. The electric power, in its turn, may be transformed into any other necessary form.

When an object loses its potential power, that power is turned into kinetic power. Thus, in the above-mentioned example when water is falling from its raised position, it certainly loses its potential power, that power changing into kinetic power (Fig. 1).

We have already seen that power of some kind must be employed to generate the electric current. The sources of power usually employed to produce current are either chemi­cal, as in the battery, or mechanical, as in the electromagnetic generator. Chemical sources of current having a limited ap­plication, the great quantities of electric power generated today come from various forms of mechanical power.

Needless to say that rising standards of modern civili­zation and growing industrial applications result in an in­creasing need of power. Every year we need more and more electric power for the useful things that are done only owing to electricity. However, the power sources of the world are decreasing at the same time as the power needs of the world are increasing. These needs will continue to grow as more motors and melted metals are used in industry and more electric current is employed in our everyday life. As a result, it is necessary to find new sources of power.

Fig. 1. Examples of kinetic power.

The Sun is an unlimited source of power. However, at present, only a little part of solar power is being used di­rectly. How can we employ solar power directly to produce useful power? This is a question which has interested scien­tists and inventors for a long time. Lavoisier and other great scientists of the past melted metals with the help of solar furnaces. Today, solar furnaces illustrate just one of the numerous ways to harness the sun. Using semiconductors, scientists, for example, have transformed solar power into electric power.

 

Exercises

Describe Fig 1.

Retell the text.

LESSON THREE

ATOMIC POWER

Man has learned to split atoms in order to get great quantities of power. In the XXth century coal was the most important fuel and the  ba­sic source of power.  At present coal and other fuel are replaced by atomic power. Atomic power replacing the present sources of power, we will get more power than we produce today.

The nuclear reactor will pos­sibly be one of the reliable "fur­naces" producing atomic power. Being used to produce power, the reactor produces it in the form of heat. In other words, heat is developed by the splitting of atoms in the reactor. Gas, water, melted metals, and some other liquids circulating through the reactor carry that heat away. The heat may be carried to pipes of the steam-generator containing water. The resulting steam drives a turbine, the turbine in its turn driving an electric genera­tor. So, we see that a nuclear power station is like any oth­er power plant but the familiar coal-burning furnace is replaced by a nuclear one. However, a ton of uranium (nuclear fuel) can give us as much power as 2 1/2 to 3 million tons of coal.

The first industrial nuclear power plant in the world was constructed in our country in 1954. It has already been working for many years. One may mention here that the plant in question was put into operation two years earlier than the British one and three and а half years earlier than the American nuclear power plants.

The Beloyarskaya nuclear power station in the Urals may serve as another example of the peaceful use of atomic power in Russia. Russian scientists and engineers having achieved a nuclear super-heating of steam directly in the reactor itself, it is certainly a new important contribution to nuclear engi­neering. By the way, such a nuclear super-heating of steam directly in the reactor before it is carried into the turbine was achieved for the first time in the world.

We may mention here another important achievement. It is the first nuclear installation where thermal power gener­ated in the reactor is transformed directly into electric power.

Exercises

LESSON FOUR

MAGNETISM

In studying the electric current, we observe the following relation between magnetism and the electric current: on the one hand magnetism is produced by a current and on the other hand the current is produced from magnetism.

The earliest practical application of magnetism was con­nected with the use of a simple compass consisting of one small magnet pointing north and south.

A great step forward in the scientific study of magnetism was made by Gilbert, the well-known English physicist (1540-1603). He carried out various important experiments on electricity and magnetism and wrote a book where he put together all that was known about magnetism. He proved that the earth itself was a great magnet.

Reference must be made here to Galileo, the famous Italian astronomer, physicist and mathematician. He took great interest in Gilbert's achievements and also studied the prop­erties of magnetic materials. He experimented with them trying to increase their attracting power. One of his magnets, for example, could lift objects weighing 25 times its own weight.

At present, we are quite familiar with the fact that in magnetic materials, such as iron and steel, the molecules themselves are minute magnets, each of them hav­ing a north pole and a south pole. These molecules usually arrange themselves in a disorderly way, their north and south poles pointing in all directions and neutralizing one another.

The process of magnetization consists of turning these little magnets until all their north poles point in one direction and south poles in the other.

When iron and steel are magnetized, the molecules arrange themselves in a new orderly way instead of the disarrangement in which they neutralize each other. Dividing a bar magnet into two parts, one finds that each of the two parts is a magnet having both a north pole and a south pole. In other words, we obtain two smaller magnets instead of our having a single one of a larger size. Dividing one of these two smaller magnets into two will give us the same result. Thus, we could continue this process, always get­ting similar results.

On placing an unmagnetized iron bar near a strong magnet, we mag­netize it. Rubbing the magnet is not required for that process. In other words, our iron bar has been magnetized by the strong magnet without rubbing it.

 Exercises

 

Speak on magnetism.

13. Compare:

1. A generator and a motor.

2. Potential power and kinetic power.

3. Chemical power and mechanical power.

4. Nuclear power station and steam power station.

LESSON FIVE

 

ELECTRIC CURRENT

Ever since Volta first produced a source of steady contin­uous current, men of science have been forming theories on this subject. For some time they could see no real difference between the newly-discovered phenomenon and the former understanding of static charge. Then the famous French scien­tist, Ampere (after whom the unit of current was named) determined the difference between the current and the static charges. In addition to it, Ampere gave the current direc­tion: he supposed it to flow from the positive pole of the source round the circuit and back again to the negative pole. We know him to be right in his first statement but he was certainly wrong in the second, as to the direction of current. The flow of current is now known to be in a direction opposite to what he thought.

 The current which flows along wires consists of moving electrons. In other words, the flow of moving electrons is one form of the electric current.  We consider the electron to be a minute particle having an electric charge. We also know that charge to be negative. As these minute charges travel along a wire, that wire is said to carry an electric current.

In addition to travelling 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 said to be d. c, that is, direct current. The simplest source of power for direct currents is a battery, for a battery pushes the electrons in the same direction all the time (i. е., from the negatively charged terminal to the positively charged terminal).       

The letters a. c. stand for alternating current. The current under consideration is known to flow 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 (Fig. 6).

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. In fact, at least 90 per cent of electric power to be generated at present is a. c. We know it to find a wide application for lighting, heating, industrial and other purposes.

In spite of the fact that almost all electrical power is usually generated and transmitted in the form of a. c, there are numerous cases when d. с is required. For this reason, it is quite possible to generate a. c. then transform it into d. с

We cannot help mentioning here that Yablochkov, our Russian scientist and inventor, was the first to apply a. c. inpractice.

Exercises

 

1. Learn the following active words and use them in the sentences of your own:

advantage (n)           преимущество

alternating current        переменный ток

decrease (v)                   понижать(ся), уменьшать(ся)

determine (v)            определять, устанавливать

direct current            постоянный ток

direction (n)                  направление

in­crease (v)                   повышать(ся), увеличивать(ся)

liquid (n)                       жидкость

particle (n)                    частица

pole (n)                     полюс

solid (n)                    твердое вещество

statement (n)                 утверждение

subject (n)                     предмет, тема

terminal (n)                   клемма

voltage (n)                     напряжение

 

Explain why:

1. static electricity cannot be used to light lamps, to boil water, to run electric trains and so on.

2. voltage is increased and decreased.

3. the unit of electric pressure is called the Volt.

4. students must learn English.

5. the flow of moving electrons is a form of the electric current.

6. Ampere was wrong as to the current direction.

7. the current is said to flow from the positive end of the wire to the negative end.

8. Define the meaning of the following words:

battery, alternating current, direct current,  static elec­tricity, electric current, wire, laboratory, terminal, electron

9. The following statements are not true to the fact. Correct them:

1. Electrons flow from the positively charged terminal of the battery to the negatively charged terminal. 2. Ampere supposed the current to flow from the negative pole to the positive. 3. Static electricity is used for practical purposes. 4. Static electricity is not very high in voltage and it is easy to control it. 5. To show that the charges are unlike and opposite Franklin decided to call the charge on the rub­ber positive and that on the glass negative. 6. Galvani thought that electricity was generated because of the contact of the two dissimilar metals used. 7. Volta took great interest in atmospheric electricity and began to carry on similar exper­iments. 8. The direct current is known to flow first in one direction and then in the opposite one. 9. The direct current is used for power and lighting purposes is assumed to go through 50 cycles a second.

LESSON SIX

ELECTRIC CIRCUIT

We know the circuit to be a complete path which carries the current from the source of supply to the load and then carries it again from the load back to the source.

Generally speaking, the current may pass through solid conductors, liquids, gases, vacuums or any combinations of these. It may flow in turn over transmission lines from the power station, through transformers, cables and switches, through lamps, heaters, motors, and so on,—back through other switches, cables, transformers and transmission lines to the generator in the power station.

There are many kinds of circuits, such as: open circuits, closed circuits, series circuits, parallel circuits and short cir­cuits.

If the circuit is broken or, as we generally say, "opened" anywhere, the current stops everywhere. Hence, we break the circuit when we switch off our electric, devices.

The path along which electrons travel must be complete or no electric power can be supplied to the load from the source. Thus, we close the circuit when we switch on our electric lamp.

A simple electric circuit is illustrated in Fig. 7. In this figure a 4-cell battery has been used, the switch being in an open position. If the switch is in a closed position, a current will flow around the circuit in the direction shown by the arrows.

To understand the difference between the following circuit connections is not difficult at all. When electrical devices are connected so that the current is not divided at any point they are said to be connected in series. Under such condition the current flow is the same in all parts of the circuit, as the is only a single path along which it may flow. Quite the opposite, the parallel circuit provides two or more paths for the passage of current. The circuit is divided in such a w«that part of the current goes through one path and pass through another.

 

Fig. 7. A simple electric circuit

We produce a short circuit or, as we sometimes call it, the "short" when we allow the current to return to the source of supply without control and without doing the work that we want it to do. In short, this phenomenon mostly results in cable faultand wire fault while under certain conditions it may even cause fires.

It is interesting to note that some substances like metals, for example, conduct electricity with ease; on the contrary, others, such as rubber, do not allow it to move freely. Thus, we obtain conductors and insulators, there being a marked difference between them, of course.

So far nothing was said about conductance, that is, the conductor's ability to pass electric charges. It appears to de­pend on four things, namely: its size, its length, the kind of material to be used, and its temperature.

It is not difficult to understand that a large water-pipe can pass much more water than a small one. We equally expect a large conductor to carry current' more readily than a thinner one. Fig. 8 illustrates this feature better than words alone! Indeed, we see that the larger the wire, the greater is its conductance because electricity meets less resistance then.

It is quite understandable too that 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 materials. Hence, the longer the wire, the greater is its opposition, that is resistance, to the passage of current.

Fig. 8. Comparing water flow and current flow.

There is a great difference in the conductance of various substances. For example, almost all metals are supposed to conduct current. Nevertheless, copper appears to carry the current more freely than iron, silver conducting better than copper. It is therefore said to have a greater conductance than copper. The reader probably remembers that insulators also differ in their insulating properties.

As to temperature, we are familiar with the following feature. As the temperature rises, opposition to the passage of current increases as well. Hence, conductance depends on the temperature of the wire.

It is quite wrong to think that conducting materials are the only materials to play an important part in electrical engineering. As a matter of fact, to meet our everyday power requirements, we are certain to need both conductors and insulators.

Exercises

1. Translate the following sentences and define the functions of the infinitive:

I. The current is known to flow when the circuit is complete. 2. To stop the flow of current is to break the circuit in some point. 3. Copper and silver are considered to be the best conductors of electricity. 4. Various switches are gener­ally used to open or to close the circuits. 5. Ampere supposed the current to flow from the positive pole of the source to the negative pole. 6. It is quite possible to generate a. c. And then transform it into d. с 7. Yablochkov was the first to apply a. c. in practice. 8. A battery is the simplest device to produce direct current. 9. We know the circuit to be a path of an electric current. 10. We may expect a short circuit to result in wire fault and cable fault.

2.      Answer the following questions:

1. What do we deal with in this article? 2. What is an electric circuit? 3. What kinds of circuits do you know? 4. When is the "short" produced? 5. What feature of the con­ductor is illustrated in Figure 8? 6. What does conductance depend on? 7. What do we mean by the term "short circuit?" 8. What does the term "closed circuit" mean? 9. Who deter­mined the difference between the electric current and the static charges? 10. Why does the current flow when the cir­cuit is closed?

3. Define the meaning of the following words:

circuit, electron, conductor, insulator, switch, current, conductance

Compare:

1. Conductors and insulators.

2. Closed circuits and open circuits.

3. Series circuits and parallel circuits.

5. Work in pairs. Put your questions and let youe fellow-students answer them.

1. if heat is a form of power.

2. if all substances are made up of molecules.

3. if the molecules are travelling in various directions in a substance,

4. if the circuit is a complete path which carries the cur­rent from the source and back to the source.

5. if all metals conduct electricity with ease.

6. if we close the circuit when we switch off the electric light.

7. if we open the circuit when we switch on the electric light.

8. if conductance depends on the temperature of the wire.

6. Translate the following sentences paying special attention to the words in bold type:

1. The faster the molecules of a substance move, the higher is the temperature of the substance. 2. The larger the water-pipe, the more water passes through it. 3. The more you»read, the more you learn. 4. The shorter the wire, the less is its resistance to current flow. 5. The greater the number of free electrons in a substance, the better that substance con­ducts electricity.

7. Fill in the blanks with the following words and expressions:
as, as well, as well as

1. It is necessary to remember the term "circuit"... it is almost impossible to work with electricity without working with circuits. 2. Copper wires are mostly used... conductors of electricity. 3. A "short" may cause wire fault... cable fault. 4. In addition to travelling through solids, the electric cur­rent can flow through liquids and gases... 5.... a cold object and a hot one are brought into contact, the former gets warm­er and the latter gets colder. 6.... a conductor becomes warmer, it is unable to pass electric charges as freely as it did before its temperature began to rise. 7. The magnitude of the current... the voltage and resistance may vary from a minute amount to a very large quantity.

8. Fill in the blanks with suitable prepositions if necessary and
make up sentences with the following infinitives:

to answer...; to apply...; to be interested...; to con­tribute...; to consist...; to depend...; to invite...; to pay attention...; to play a part...; to go...; to be followed...

9. Translate the following sentences:

1. Я не могу не ответить на этот вопрос. 2. Он не может не упомянуть об этом. 3. Мы не могли не вспомнить о пожаре, вызванном коротким замыканием. 4. Она не может, не думать о своей исследовательской работе. 5. Я не могу не знать, что короткое замыкание может вызвать поврежде­ние провода.

10. Speak on:

1. The properties of the electric circuit.

2. The conductors of electricity.

3. The insulators of electricity.

LESSON SEVEN

Exercises

1.Learn the following active words:

deficiency                      недостаток, дефицит

disorderly                     беспорядочный

electromotive force       электродвижущая сила

(e.m.f.)                         (ЭДС)

excess (n,a)                   избыток, избыточный

influence (v)                  влиять

offer (v)                    оказывать

potential difference       разница потенциалов

photocell                       фотогальванический элемент

resistance                      сопротивление

same                         тот же самый, одинаковый

suspend                    подвешивать      

thermocouple           термопара

             

Conditional Sentences

I	If atomic power replaces the present sources of power, we shall get more power than we produce
II	If atomic power replaced the present sources of power, we should get more power.
III	If Professor Rihman had thought of the possible danger, lightning would not have killed him

 

2. Translate the following sentences:

A. 1. If an emf is applied to a path which allows the electrons to pass, they will move toward the point of higher potential, and then a current is said to flow in the circuit.
2. If people of the past had known that lightning was atmospheric electricity, they would not have invented numerous stories. 3. If a wire is held against an electrified body, electri­city would flow along the wire to the other end. 4. If coal were not used as fuel, we should get more valuable products.

B. 1. Were that liquid heated, it would greatly expand. 2.Were there no flow of current between A. and B. in any direction, then A. and B. would be at the same potential. 3. Were the electromotive force alternating, the current would be alternating as well. 4. Should we break the circuit, no current would flow. 5. Should they use a large water pipe, more water would pass through it.

3. Translate the following sentences paying special attention to the word provided:

1. These electrical devices are provided with rubber in­sulators. 2. These electrical devices provided with rubber insulators were produced at a large factory. 3. These electrical devices can work for a long time, provided they are made of good material. 4. The electric current flows provided there is a complete circuit. 5. Lightning did not strike the house as it was provided with a lightning conductor. 6. Ohm's law pro­vided the possibility of determining resistance provided the voltage and current are known. 7. The electrons will jump through the air forming an electric spark, provided the poten­tial difference becomes great enough. 8. The students will be able to translate difficult articles, provided they have dictionaries.

4. Fill in the blanks with prepositions and translate the follow­ing text:

The great French physicist, Ampere, was an absent-mind­ed man. One day he was waiting... his friend. The appointed hour arrived, passed and his friend did not come. As Ampere had to go... he took a piece... chalk and wrote... his door: "I have gone.... I shall return... two hours." And he went away.

He returned two hours later. While he was going upstairs he worked out a very difficult problem.

"If my friend had come... the appointed hour," he said... himself, "I should have told him... this problem. I shall speak... him... it now. Perhaps he will be able to solve it." So when he came... his own door and saw the words written... it, Ampere decided that he was... his friend's door. "Oh," said he, "he has gone...! I am very sorry! Were he... home, we should discuss my problem." And he wrote the following words: "Very sorry that I have not found you... home." Then he went downstairs again.

Had Ampere not been an absent-minded man he would have never made such a mistake.

5. Complete the following sentences:

a)

1. If my friend comes to Moscow, we...

2. If I had time tomorrow, I...

3. If my friend had not entered the Institute last year, he...

4. If I were you, I...

5. If the teacher had given me the dictionary, I...

6. If my brother goes to England, he...

b)

1. Не would have done it, unless...

2. We should have gone to the country yesterday, pro­vided...

3. I should finish my work in time tomorrow unless...

4. She will answer all the teacher's questions, provided...

6. Fill in the blanks with among or between:

1. The Voltaic pile consisted of copper and zinc placed one above another, with flannel moistened in salt water... them. 2. A wire was connected... the first disc of copper and the last disc of zinc. 3. There is a great difference... conductors and insulators of electricity. 4. There are many good conductors; copper and silver are... the best ones. 5. I found your dictionary... my books. 6. The scientist de­termined the difference... the two methods.

7. Translate the following words and expres­sions into English:

обращать внимание; на основе чего-л.; электротехника; по этой причине; удовлетворять требованиям; совсем не трудно; тем не менее; наоборот; оказывать сопротивление; в таких условиях; происходить

8. Put all possible questions to the following sentences:

1. The excess electrons will flow towards the point of deficiency.

2. The parallel circuit provides two or more paths for current flow.

9. Apply suitable adjectives to the following nouns.
Model: natural phenomena

difference, spark, force, wire, factor, resistance, conductor, ball

10. Form new words of the same root, define what parts of speech they are:

active, to differ, real, ease, conductance, resist

11. Speak on:

1. Potential difference.

2. Electromotive force.

3. Resistance.

LESSON EIGHT

GENERATORS

Great generators in our power stations, which rotate at a constant speed day and night, summer and winter, are able to generate electric power only because of the electromagnets.

It is calculated that these machines produce more than 99.99 per cent of all the world's electric power.

Although used to operate certain devices requiring small currents for their operation, batteries and cells are unlikely to supply light, heat, and power on our modern large scale. It is dynamo-electric machines that are used for this purpose. These are machines by means of which mechanical power is turned directly into electric power with a loss of only a few per cent.

There are two types of dynamos, namely, the al­ternator and the generator (Fig. 11). The former pro­vides a. c. while the latter supplies d. c, similar to the current from a battery. Both of them must be turned by some outside source of me­chanical power, such as, water power, for example. 'Where cities are far from water power, the mechanical power for the generator mostly comes from burning coal, which operates a steam turbine which turns the generator. Both-generators and alternators consist of the following principal parts: an armature and an electromagnet. The for­mer generally serves as a rotor in d. с generators while it is the magnetic system that serves this purpose in alternators. The latter is usually called a stator for it is in a static condi­tion "In order to get a strong e. m. f., the rotors in large alternators rotate at a speed of thousands of revolutions per minute (г. р. т.). In this connection one could add that the speed of rotation will control the output voltage of the gen­erator in the following manner:

1. The faster the armature is rotated, the more voltage the generator will produce.

 2. The slower the rotation, the less the output voltage. Electric power stations which supply electricity over longdistances are at present always equipped with large alter­nators. These supply us with much greater quantities of cur­rent than anything ever supposed by Volta, Oersted and Ampere. 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. As you are likely to remember, the Kuiby­shev and Volgograd stations have 125,000 kil­owatt generators and the Bratsk hydroelec­tric station has twenty 225,000 kilowatt generators.

 

Russian scientists are known to develop 500,000 kilo­watt generators which are to be installed at the Kras­noyarsk station.

Large installations with turbo-generators of 200,000 to 300,000 kW power are being constructed in different parts of Russia. The eight generators of the Konakovo thermo-electric station not far from Moscow are planned to have 2,400,000 kW of rated capacity.

Our industry is most likely to produce even greater power installations for thermo-electric stations which play such an important part in energy supply of our country..

It goes without saying that the dynamo invented by Fa­raday in 1831 would seem to be a most primitive apparatus compared with the powerful, highly-efficient machines that are in use today. Nevertheless, these generators and alterna­tors work on the same principle as the one invented by the great English scientist. When asked what use his new inven­tion had, Faraday is said to have asked in his turn: "What is the use of a new-born child?" As a matter of fact, the "newborn child" soon became an irreplaceable device we cannot do without.

Fig. 11 shows the principles the construction of an ele­mentary d. с generator is based upon. We see the armature, the electromagnet, the shunt winding, the commutator and the load.

Exercises

1. Learn the following active words:

alternator                 генератор переменного тока

armature                        якорь

calculate                        считать

equip                   оснащать, оборудовать

operate                работать, функционировать

revolutions per minute  обороты в минуту

rotate                   вращаться

shunt                       шунт, параллельная цепь

thermo-electric station термоэлектростанция

tur­bine                     турбина

winding                    обмотка

2. Translate the following sentences:

1.Heat developed in a transmission line or a generator is a needless waste of power. 2. An electric lamp uses the light given off by its filament heated by the current. 3. The experiments made by Oersted attracted Ampere’s attention. 4. Electric power stations supplying power on a large scale are equipped with large alternators.

3.Translate the following sentences and combine the principal and the subordinate clauses with suitable conjunctions:

1. There is a great number of engineering problems the Russian scientists work at. 2. It is quite impossible to name a scientific problem 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.

4. Answer the following questions:

1. Do you want to translate this article? 2. Do you want me to translate this article? 3. Do you know this scientist? 4. Do you know this scientist to have explained the new phenomenon? 5. Did you hear my report? 6. Did you hear my friend make a report? 7. Did you see my brother? 8. Did you see my brother enter the room?

5. Form adjectives using the suffixes -able, -fut, -less, -ous:

control, continue, danger, value, replace, need, power, peace, use, life

6. Form adverbs using the suffix -ly:

exact, electrical, general, gradual, negative, natural, opposite, previous, usual, easy

7. Read the following abbreviations:

а. c, d.c, r.p.m., e.m.f., 317°F, 45°C, i.e.

8. 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 короче проводник, тем меньше со­противление проходящему току. 5. Чем больше скорость движения между магнитным полем и проводниками, тем больше ток.

9. Define the following terms:

1. electromotive force; 2. electric circuit; 3. heating effect of an electric current; 4. magnetic effect of an electric current; 5. electromagnet; 6. generator

LESSON NINE

POWER TRANSMISSION

One reason electricity serves us so well is that it can be generated in a suitable locality, transmitted over long distances, and supplied with almost unchangeable power to exactly the locality where it is wanted, i.e., where we want to use it and wherever wires can pass.

Until a hundred years ago, or so, power was never carried far away from its source. Later on, the range of transmission was expanded into 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 power into electrical power and transmit it over hundreds of kilometres and more in any direction required. Then, electric power may be reconverted into mechanical power whenever and wherever it is desirable. It is not difficult to understand that the above process has been made possible owing to the generators, transformers, and motors, as well as to other necessary electrical equipment. We should also name here Dolivo-Dobrovolsky, the outstanding Russian electrical engineer, who was the founder of the three-phase technique. It was his invention that made possible the long-distance power transmission and, hence, electrification in the real sense of the word.

You will find below two examples illustrating the growth of electric power generation in our country: perhaps, you are familiar with the fact that the longest transmission line in prerevolutionary Russia was that connecting the Klasson Power Station with Moscow. It is said to have been built 70 km long.

Generally speaking, the length of high-tension transmission lines in our country is so great that they could cir­cle the globe six times.

It goes without saying that as soon as electric power is produced at the pow­er station, it is to be transmitted over wires 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. We can lower these undesirable losses in two ways, namely, we can reduce either the resistance, or the current. It is easy for us to see how one can reduce re­sistance: it is necessary to make use of better conducting material and as thick wires as possible. However, such wires would require too much material and, hence, they would be too expensive. Can the current be reduced? It is quite possible to supply the consumer with the amount of power he needs and at the same time to reduce the current in the transmission line by employing transformers. In effect, the unnecessary waste of useful power has been greatly decreased due to high-voltage lines, so that one may transmit power over long distances with small loss. 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 lowered again before the power is made use of.

Exercises

1. Learn the following active words:

amount to (v)               доходить, равняться

considerable (a)        значительный

distribution (n)                  распределение

equipment (n)               оборудование

expensive (a)               дорогостоящий

lower (v)                   понижать

range (n)                   диапазон

reduce (v)                 понижать, уменьшать

successfully (adv)      успешно

suitable (a)               подходящий, пригодный

tension (n)                напряжение

wave (n)                            волна

2. Translate the following sentences paying special attention to the impersonal construction:

(a) 1. It is easy to understand Ampere's rule. 2. It was desirable to compare the results obtained. 3. It is necessary to find new sources of power. 4. It was difficult for Oersted to find out why the compass needle was deflected.

(b) 1. One can say that there are unlimited sources of power. 2. One could not obtain good results without repeat­ing the test. 3. If one could count one atom a second day and night, it would take one hundred milliard years. 4. One may mention here that the first industrial nuclear power plant in the world was constructed in this country.

(c) 1. They employ different methods to obtain better results. 2. They produce modern machines at our plant. 3. They say that lasers will be widely used in the nearest future.

(d)1. It is supposed that people learned to protect their houses from thunderstorms years ago. 2. It is said that these substances have similar properties. 3. It is well known that one form of power can be changed into another.

3. Answer the following questions:

I. What made it possible to transmit electric power over hundreds of kilometres? 2. What are transformers used for? 3. What contribution did Dolivo-Dobrovolsky make to elec­trical engineering? 4. What do you know about the longest transmission line in the pre-revolutionary Russia? 5. How long is the Samara-Moscow high-tension transmission line? 6. In what way can the heating losses be lowered in transmis­sion lines? 7. How can resistance be reduced in electric wires? 8. Why are high-voltage lines used for power transmission?

4. Complete the following sentences:

I. Owing to the transformer it became possible... 2. It was Dolivo-Dobrovolsky 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 power can be de­creased... 6. Coal is burned in order to...

5. Define the meaning of the following words:

power station, nuclear reactor, transmission line, sole­noid, electromagnet

6. Choose the right term and explain the statement:

1. The coil of wire that rotates in a dynamo or a motor s known as: (a) a turbine, (b) a stator, (c) an armature, d) a generator.

2. Running water is an illustration of: (a) potential power, (b) kinetic power, (c) electric power, (d) heat power.

3. Steam turbine generators produce electrical power from: (a) potential power, (b) chemical power, (c) light power, (d) mechanical power.

7. Translate the following text:

Storage Batteries

Storage batteries are made up of a number of rechargeable cells, often called secondary cells to distinguish them from primary cells. Secondary cells are made of several different materials, but all work on the principle of reversible chemical action between two dissimilar electrodes (plates) impressed in an active solution (electrolyte). Particular battery designs are, of course, much more complicated and have several plates in parallel, closely packed with insulating separators.

Retell the text.

LESSON TEN

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, provided 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 spoken about 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.

The primary alternating current produces an alternating magnetic flux in the iron core, and this alternating magnetic flux passes through the turns of the secondary winding. Accord­ing to well-known electro-magnetic laws, this flux produces an alternating e. m. f., or voltage, in the secondary winding. In spite of the fact that there is no electrical connection be­tween the two circuits - the primary and the secondary - the application of a voltage to one is known to produce a voltage at the terminal of the other.

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. One should add in this connection that to "step up" means to in­crease the voltage. On the contrary, to "step down" means "to reduce".

A 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.

Inefficiency in a transformer is caused mainly by heat losses due not only to current flowing in the coils, but also to unwanted current induced in the core of the transformer.

 

Currents induced in the core are generally called "eddy cur­rents." The flow of eddy currents is stopped in its progress and the efficiency of the transformer is increased by constructing the transformer core of flat sheets of soft iron,

In Fig. 13 it is seen how transformers are used in stepping up the voltages for distribution or transmission over long distances and then in stepping these voltages down, where they are to be used. In this figure, one may see three large step-up transformers which 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. е., 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 arid lamps. One could have some other transformers in the system, such as those to be employed for operating door bells or powering radio sets and television sets, for example. They lower the voltage even further. On the whole all radio sets and all television sets are known to use two or more kinds of transformers. These familiar examples of electronic equip­ment could not work without transformers. The facts you have been given above illustrate the wide use of transformers and their great importance.

Another alternating-current system of transmission and distribution is shown in Fig. 14. You are asked to follow the whole process,, that is, to describe it from beginning to end.

 

Exercises

1. Learn the following active words:

Damage                         повреждение

eddy current                  вихревой ток

flux                               течение, поток

induce                           вызывать, стимулировать

input                             подводимый ток

maintenance                  тех. обслуживание

output                           выход, выработка

primary                         первичный

secondary                     вторичный

2. Translate the following sentences:

(a) 1. The new discovery was much spoken about. 2. This house is lived in. 3. This apparatus is often made use of.

(b)1. The students were asked to carry on the experiment. 2. You will be given two new magazines. 3. I was told to translate the instructions.

(c) 1. This substance was supposed to have some important features. 2. This device is assumed to be the best for converting heat into work. 3. The new power plant is known to have been put into operation. 4. This invention was considered to be of great practical importance. 5. A magnetic flux is assumed to consist of magnetic lines of force taken as a whole.

3. 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 Ломоносов основал Москов­ский университет. 5. Кажется, что это вещество имеет некоторые другие свойства. 6. Известно, что переменный ток меняет свое направление.

4.      Form as many words as possible using suffixes and prefixes. De­fine what parts of speech the new words are and translate them:

engine, apply, differ, electrify, value, opposite, trans­former, magnet, conductance

5. Form nouns from the following verbs using either suffix –ment or -tion:

construct, develop, consider, distribute, deflect, equip, connect, require, produce, state                                                       

6. What is the English equivalent for the following:

на основе (чего-либо), теплотехника, по этой причине само собой разумеется, повышать напряжение, повышать ток, понижать ток, оказывать сопротивление

7. Arrange the following words and expressions in pairs of syno­nyms:

(a) amount, among, matter, application, at present, engine, tube

(b) now, pipe, quantity, substance, between, use, machine

8. Arrange the following words and expressions in pairs of antonyms:

(a) left, increase, beginning, d.c., above, step-up, at rest, high, short, more

(b) end, low, long, step-down, in motion, less, decrease, below, a.c., reght

9. Form statements that are not true to the fact. Ask other students
to correct them.

10. Translate the following sentences paying special attention to
the words in bold type:

1. The Fahrenheit scale is mainly used in English-speaking countries but it is not used in our country. 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 our daily life. 4. There is but one measuring scale in the instrument. 5. Everyone took an exam­ination in physics but that student. 6. A simple trans­former is but a kind of an induction coil.

11. 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.

LESSON ELEVEN

THE ELECTRIC MOTOR

The electric motor is a device employed for transforming one form of power into another, that is to say, electrical into mechanical. We know it to produce the rotary motion which turns our machinery and various appliances.

We have already seen the generator convert mechanical power into electric power. Now, the process is reversed. It is electricity that is supplied to the machine and it is motion that results. From all that has been said earlier in the previous articles about our getting magnetism from electricity and about the generation of the electric current by using magnet­ism, it is obvious that generators and motors are similar in certain respects. In case we put current into the dynamo instead of our taking current out, it will rotate as a motor. There are certainly some differences in detail but in both of them we find an armature with windings, a commutator and brushes, combined with an electromagnet for producing the magnetic field. However, in an electric motor one shunt winding is not sufficient and a second one called a series winding should be added. "Why is it necessary?" one might ask. The fact is that the motor is required to have a powerful effect at the very moment when the current is switched on, as for instance, in an electric tram or a train. A very strong magnetic field is needed to obtain a so-called powerful starting torque. This is achieved by adding a series winding to the magnet coils (Fig. 15). It is connected not in shunt with the armature but in series with it, so that all the heavy starting current passing through the armature winding, now passes

through the series field coil and provides a strong field neces­sary for starting while the shunt field winding provides the running conditions.

So far nothing was said of what a motor does in our homes. In a modern home there are many different electric motors in machines and devices utilized to meet our daily require­ments: to tell the time, to wash clothes, to cool the refrigera­tor, to clean or brush various things, to shave, to circulate air in a warm room on a hot summer day, and so on. In effect, vacuum-cleaners, washing machines, modern refrigerators,— all work thanks to electric motors. It follows that in the elec­tric motor we have a valuable and powerful appliance capable of fulfilling the required operations exactly and with just the desirable kind of motion, rate of speed, and power. It is readily switched on, at will, and it continues running until we switch it off again. In our present-day wide use of the motor there are often cases when it is simply impossible to replace it by any other suitable engine. Generally speaking, it revolution­ized industry by making use of power that can be transmit­ted from great distances.

No appliance ever created by man has probably such a wide range of size and such a variety of application as a motor. In fact, on the one hand, there are all kinds of mighty giants in the motor world. These giants are known to perform innume­rable operations in coal-mines, in steel mills, chemical facto­ries and so on, in short, in great numbers of factories and works. On the other hand, there exist all kinds of small-sized and even minute motors which are able to power various complex ma­chines. They operate equally well under any conditions: high in the air or immersed in water, lowered into a well or on the table of some famous scientist. Much of our farm equip­ment is also driven by means of electric motors. In short, they find an application wherever and whenever suitable, that is, in industry and science, in agriculture and transport.