English for electrical engineers. Учебное пособие на английском языке для аудиторной и самостоятельной работы студентов по направлению 13.03.02 – элек

3.Analog signals are not continuous but consist of numerous bursts of electric current between two voltage levels.

4.In the computer’s central processor the data codes are subjected to process of binary arithmetic or are compared with each other to obtain the results required by the program.

5.Semiconductors are substances whose electrical resistance lies between that of conductors and insulators.

6.Doping with an element that has only three outer electrons produces a crystal lattice without any spaces.

7.Get ready to answer the following questions.

1.What is electronics?

2.What are electric signals produced by?

3.How many types of electric signal are there?

4.What signals does a computer use?

5.What do digital signals consist of?

6.In what ways may electric signals be processed in modern electronics?

7.What is semiconductor?

8.What does doping involved?

9.What is a transistor?

10.How many types of transistors do you know?

8.Get ready to retell the text.

Text 3

1.Read, write down and learn the words and word combinations to amplify - усиливать, расширять

to announce — объявлять, заявлять triode - триод

to challenge - бросать вызов

ragged - неровный, твердый, стойкий unheard-of- неслыханный

receiver - приемник; резервуар

to seem destined to become - кажется, суждено стать

2.Read and translate the text:

TRANSISTORS

In 1948 a revolutionary concept was introduced to the electronics world: the invention of the transistor, a crystal which amplified, was announced. Nothing like this had happened in electronics since the discovery of the triode vacuum tube in 1907; some years later radio tubes replaced the crystal detectors of the wireless era.Now a crystal amplifier, the transistor, challenges the vacuum tube because transistors are smaller, simpler, more efficient, more rugged and longer lived. Already transistors have replaced tubes in hearing aids, with unheard-of battery economy. Moreover, many transistor circuits have fewer components than the vacuum tube circuits, such as multi vibrators. For example, in switching circuits, such as multi vibrators, one point-contact transistor will do the work of two triode tubes.

The transistor is a current-operated device, whereas the vacuum tube is a voltage-operated device. The transistor seems destined to become a relatively high current, low-voltage device,

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although the vacuum tube is a high-voltage, low current device. Transistors, because of their desirable properties, shortly may replace electron tubes to a large extent in communication equipment, computers, radio and television receivers

3.Give the Russian for

1.the invention of the transistor

2.triode vacuum tube

3.a crystal amplifier

4.to challenge

5.to be rugged

6.hearing aids

7.transistor circuits

8.a current-operated device

9.communication equipment

10.radio and television receivers

4.Give the English for

1.революционное понятие

2.триодная вакуумная трубка

3.кристаллический усилитель

4.неслыханная экономия батареек

5.цепи транзистора имеют меньше компонентов, чем цепи вакуумной трубки

6.прибор, работающий от тока

5.Read the text again and put in the missing words

1.In 1948 the _______ was invented. 2. Nothing, like this had happened in electronics since the discovery' of the ______ vacuum tube in 1907. 3. Now crystal amplifier, the transistor, ______

the vacuum tube because transistors are smaller, simpler, more efficient more ____.4. Many transistor

______ have fewer components than the vacuum tube circuits, such as multi-vibrators. 5. Transistors may replace electron tubes to a large extent in communication equipment, _____, and_____. 6. The transistor is a _____ -_____device.

6.Translate into Russian paying attention to the words "because" and "because of”

1.Energy resources of Russia are very large because of the great power potential in Siberia.

2. World energy resources are practically unlimited because we have studied only a small part of the mineral wealth of the earth. 3. Electronics is useful to industry and science because a physical condition - temperature, weight, viscosity and thickness - can be converted into an electric signal. 4. All electrical effects are really electronic, because all electric currents result from the movement of electrons, and all electric charges appear because of accumulation of electrons.

7.Get ready to answer the following questions

1.When were transistors invented?

2.When was the triode vacuum tube discovered?

3.What is the difference between the transistor and the vacuum tube?

4.Why does the transistor challenge the vacuum tube?

5.What can you say about the destiny of transistors?

8.Get ready to retell the text

Text 4

1. Read, write down and learn the words and word combinations amplification - увеличение, расширение

gain - усиление

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resistivity - удельное сопротивление range - ряд, предел (колебаний)

forward - передний, передовой; ускорять, способствовать to restrict - ограничивать

reverse - обратный, перевернутый back direction - обратное направление germanium - германий

valence – валентность

2. Read and translate the text:

SEMICONDUCTORS

A transistor is an active semiconductor device with three or more electrodes. By active we mean that the transistor is capable of current gain, voltage, amplification and power gain. A transistor is an electron device, in which electronic conduction takes place within a Semiconductor.

A semiconductor is an electric conductor with resistivity in the range between metals and insulators, in which the electrical charge carrier concentration increases with increasing temperature over some temperature range.

The resistivities of semiconductors and insulators decrease rapidly with rising temperatures, while those of metals increase relatively slowly. Unlike metals and insulators, the resistivity of semiconductors depends upon the direction of current flow. The direction of easiest current flow or lowest resistivity is called the forward direction, the direction of restricted current flow or highest resistivity is known as the reverse or back direction.

Semiconductors, such as the elements germanium and silicon, possess two types of current carriers, namely, negative electrons and positive holes. A hole is a mobile vacancy in the electronic valence structure of a semiconductor, which acts like a positive electronic charge with a positive mass.

3.Give the Russian for

1.an active semiconductor device

2.to be capable of current gain

3.voltage

4.an electric conductor

5.resistivity in the range between metals & insulators

6.to depend upon the direction of current flow

7.the forward direction .

8.the back direction

9.to possess two types of current carriers

10.a hole

4.Give the English for

1.изолятор

2.положительная масса

3.удельное сопротивление проводников зависит от направления тока

4.концентрация носителя электрического заряда

5.усиление тока

6.германий и кремний имеют два типа носителя тока: отрицательные электроны и положительные отверстия

5.Read the text again and put in the missing words

1.A _______ is an active semiconductor device with three or more electrodes. 2. A _____ is an electric conductor with _____ in the range between metals and insulators. 3. In the semiconductor the electrical charge carrier concentration _____ with increasing temperature over some temperature

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range. 4. The resistivities of semiconductors and insulators _____ rapidly with rising temperatures.

5.A is a mobile vacancy in the electronic, _____ structure of a semiconductor.

6.Answer the following questions

1.Is a semiconductor defined as an electric conductor?

2.Do semiconductors vary greatly in appearance?

3.May transistors replace vacuum tubes?

4.Does the state of substances depend on temperature and pressure?

5.Will you study electronics this year?

6.Have many human activities played a part in scientific inventions?

7.Did the ancients know anything about electricity?

7.Get ready to retell the text

Text 5

1. Read, write down and learn the words and word combinations

conductivity - удельная проводимость; электропроводность intermediate - промежуточный boron - бор

selenium - селен phosphorus - фосфор gray tin - серое олово hardness - твердость brittleness - хрупкость

fracture - перелом, трещина resemble - быть похожим thermal - термический

2. Read and translate the text:

THE DESTINY OF SEMICONDUCTORS

A semiconductor is often defined as an electric conductor that has a conductivity intermediate between that of an insulator and that of a metal. The more important semiconductors are: boron, germanium, silicon, selenium, phosphorus, gray tin and others.

The mechanical properties of semiconductors vary greatly. However, in hardness, brittleness, and fracture strength, semi-conducting crystals resemble insulating crystals more than they do metals. Besides their electric properties, which in themselves may be of great variety, semiconductors vary in such physical qualities as magnetism, specific heat and thermal conductivity.

Semiconductors are widely used in electronics. They challenge vacuum tubes in many applications in the electronic industry. Engineers and physicists are going to solve many engineering problems by means of semiconductors.

3.Give the Russian for

1.conductivity intermediate between that of an insulator and that of a metal

2.selenium

3.gray tin

4.chemical properties of semiconductors

5.to vary greatly

6.brittleness

7.fracture strength

8.to resemble

9.insulating crystals

10.physical qualities

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4.Give the English for

1.полупроводник определяют часто как электрический

2.проводник с удельной проводимостью металла и изолятора

3.механические свойства полупроводников сильно отличаются

4.походить

5.изолирующие кристаллы

6.электрические свойства

7.теплопроводимость

8.полупроводники широко используются в электронике

9.решать проблемы инженерии

5.Read the text again and put in the missing words

l. The more important _____ are boron, germanium, silicon, selenium, phosphorus, gray tin and others. 2. The mechanical properties of semiconductors _____ greatly. 3. Semi conducting crystals _____ insulating crystals more in _____, _____ and _____. 4. Semiconductors vary in such

_____ as magnetism, specific heat and thermal conductivity. 5. Semiconductors have a _______

intermediate between that of an insulator and that of metal.

6.Ask questions on the text and answer them

7.Get ready to retell the text

Text 6

1. Read and translate the text:

CONDUCTORS AND INSULATORS

All substances have some ability of conducting the electric current, however, they differ greatly in the ease with which the current can pass through them. Solid metals conduct electricity with ease while non-metals do not allow it to flow freely. Thus, there are conductors and insulators. What do the terms "conductors" and "insulators" mean? This difference is expressed by what is called electrical conductivity of the body. It depends upon the atomic constitution of the body. Substances through which electricity is easily transmitted are called conductors. Any material that strongly resists the electric current flow is known as an insulator.

Conductance, that is the conductor's ability of passing electric charges, depends on the four factors: the size of the wire used, its length and temperature as well as the kind of material to be employed. A large conductor will carry the current more readily than a thinner one. To flow through a short conductor is certainly easier for the current than through a long one in spite of their being made of similar material. Hence, the longer the wire, the greater is its opposition, that is resistance, to the passage of current.

There is a great difference in the conducting ability of various substances. Almost all metals are good electric current conductors. The best conductors are silver, copper, gold and aluminum. Nevertheless, copper carries the current more freely than iron; and silver, in its turn, is a better conductor than copper. Copper is the most widely used conductor. The electrically operated devices are connected to the wall socket by copper wires.

A material which resists the flow of the electric current is called an insulator. The higher the opposition is, the better the insulator is. There are many kinds of insulation used to cover the wires. The kind used depends upon the purposes the wire or cord is meant for. The insulating materials generally used to cover the wires are rubber, asbestos, glass, plastics and others. The best insulators are oil, rubber and glass. Rubber covered with cotton, or rubber alone is the insulating material usually used to cover desk lamp cords and radio cords. Glass is the insulator to be often seen on the poles that carry the telephone wires in city streets. Glass insulator strings are usually suspended from the towers

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of high voltage transmission lines. One of the most important insulators of all, however, is air. That is why power transmission line wires are bare wires depending on air to keep the current from leaking off.

Conducting materials are by no means the only materials to play an important part in electrical engineering. There must certainly be a conductor, that is a path, along which electricity is to travel and there must be insulators keeping it from leaking off the conductor.

2. Give the Russian equivalents for the words and word combinations below:

1)conductors;

2)insulators;

3)transmit;

4)resistance;

5)passage of current;

6)socket;

7)to connect to;

8)cord;

9)high voltage transmission line;

10)leak off

3. Find in the text the sentences with the following related words and translate them:

conducting – conductor – conductivity – conductance

4. State questions to the underlined words:

Solid metals conduct electricity with ease.

Conductance depends on the four factors.

There are many kinds of insulation used to cover the wires.

Insulators keep electricity from leaking off the conductor.

Conductors play an important role in electrical engineering.

5. Say whether these sentences are true or false:

Electrical conductivity of a body depends upon its atomic constitution. There is no difference in the conducting ability of various substances. The longer the wire is the weaker its opposition is.

The kind of the insulating material depends upon the purpose it is meant for. Conductors are substances through which electricity is easily transmitted. Insulators do not allow the electric current to flow freely.

6.Ask questions on the text and answer them

7.Get ready to retell the text

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ADDITIONAL READING

ELECTRIC LINES AND THEIR EFFICIENCY

Wires are used to deliver electric power and to interconnect different components of electrical installations. Conductors used for electric wiring are commonly produced of copper and aluminium. Aluminium is widely used nowadays due to its low cost. Copper is also widely used in electrical engineering but its cost is much higher.

Cross-sections of copper conductors used nowadays are from 0.5 up to 800 sq mm. Aluminium conductors have the same cross-sections but the minimum one is 2-5 sq. mm.

Wires connecting the components of various, installations may be insulated. They may also be used without insulation. Since in short lengths of wire power loss is exceedingly low one can ignore it. In long wires (longer than 10 m), power loss cannot be ignored since it is rather high. Power loss in a line should not exceed a certain value. If this value is exceeded the line becomes inefficient.

One should know that the efficiency of a line is not constant-it may change. The value of the line efficiency depends on the load: the greater the load the lower is the line efficiency. At voltage losses of 2 to 5 per cent the efficiency of a line is 98-95 per cent. Protecting devices, fuses and relays, are used to protect the circuit against overcurrents and short-circuits.

ELECTRIC GENERATORS AND MOTORS

Other important energy-conversion devices emerged during the 19th century. During the early 1830s the English physicist and chemist Michael Faraday discovered a means by which to convert mechanical energy into electricity on a large scale. While engaged in experimental work on magnetism, Faraday found that moving a permanent magnet into and out of a coil of wire induced an electric current in the wire. This process, called electromagnetic induction, provided the working principle for electric generators.

During the late 1860s Zénobe-Théophile Gramme, a French engineer and inventor, built a continuous-current generator. Dubbed the Gramme dynamo, this device contributed much to the general acceptance of electric power. By the early 1870s Gramme had developed several other dynamos, one of which was reversible and could be used as an electric motor. Electric motors, which convert electrical energy to mechanical energy, run virtually every kind of machine that uses electricity.

All of Gramme's machines were direct-current (DC) devices. It was not until 1888 that Nikola Tesla, a Serbian-American inventor, introduced the prototype of the present-day alternating-current (AC) motor.

DIRECT ENERGY-CONVERSION DEVICES

Most of these energy converters, sometimes called static energy-conversion devices, use electrons as their “working fluid” in place of the vapour or gas employed by such dynamic heat engines as the external-combustion and internal-combustion engines mentioned above. In recent years, direct energy-conversion devices have received much attention because of the necessity to develop more efficient ways of transforming available forms of primary energy into electric power. Four such devices—the electric battery, the fuel cell, the thermoelectric generator (or at least its working principle), and the solar cell—had their origins in the early 1800s.

The battery, invented by the Italian physicist Alessandro Volta about 1800, changes chemical energy directly into an electric current. A device of this type has two electrodes, each of which is made of a different chemical. As chemical reactions occur, electrons are released on the negative electrode and made to flow through an external circuit to thepositive electrode. The process continues until the circuit is interrupted or one of the reactants is exhausted. The forerunners of the modern dry cell and the lead-acid storage battery appeared during the second half of the 19th century.

The fuel cell, another electrochemical producer of electricity, was developed by William Robert Grove, a British physicist, in 1839. In a fuel cell, continuous operation is achieved by feeding fuel (e.g., hydrogen) and an oxidizer (oxygen) to the cell and removing the reaction products.

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Thermoelectric generators are devices that convert heat directly into electricity. Electric current is generated when electrons are driven by thermal energy across a potential difference at the junction of two conductors made of dissimilar materials. This effect was discovered by Thomas Johann Seebeck, a German physicist, in 1821. Seebeck observed that a compass needle near a circuit made of different conducting materials was deflected when one of the junctions was heated. He investigated various materials that produce electric energy with an efficiency of3 percent. This efficiency was comparable to that of the steam engines of the day. Yet, the significance of the discovery of the thermoelectric effect went unrecognized as a means of producing electricity because of Seebeck's misinterpretation of the phenomenon as a magnetic effect caused by a difference in temperature. A basic theory of thermoelectricity was finally formulated during the early 1900s, though no functional generators were developed until much later.

In a solar cell, radiant energy drives electrons across a potential difference at a semiconductor junction in which the concentrations of impurities are different on the two sides of the junction. What is often considered the first genuine solar cell was built in the late 1800s by Charles Fritts, who used junctions formed by coating selenium (a semiconductor) with an extremely thin layer of gold (see Exploiting renewable energy sources below).

TYPES OF D.C. GENERATORS

The d.c. current in the field coils is called the 'excitation current', and may be supplied either from a separate d.c. voltage source, or by using the d.c. output of the generator itself. If the field is supplied with current from an external source, the generator is said to be 'separately-excited'; but if some of the generator output is used to supply the field current, it is said to be 'self-excited'. In a selfexcited generator the field coils may be connected either in series with the armature coils ('series'), in parallel with the armature coils ('shunt'), or partly in series and partly in parallel with them ('compound').

Separately-excited d.c. generators have two circuits: the field current, consisting of the field coils connected across a separate d.c. source, and the armature circuit, consisting of the armature coil and the load resistance. In the generators of this type the field is independent of the armature, since it is supplied with current from either another generator (exciter), an amplifier or a battery. The separately-excited generator is frequently used in automatic motor control systems. In such systems the field current is controlled by an amplifier, and the output of the generator supplies the current which drives a motor.

In a series generator the field coils are connected in series with the armature so that the whole armature current flows through both the field and the load. If the generator is not connected across a load, the circuit is incomplete and no current will flow to excite the field. The series field winding contains relatively few turns of wire.

A shunt d.c. generator has its field winding connected in shunt (in parallel) with the armature. Therefore the current through the field coils is determined by the terminal voltage and the resistance of the field. The shunt field windings have a large number of turns and require a relatively small current to produce the necessary field flux.

A compound generator is a combined series and shunt generator. There are two sets of field coils – one in series with the armature, one in parallel. One shunt coil and one series coil are always mounted on a common pole piece. If the series field is connected so that its field aids the shunt field, the generator is called cumulatively compound. If the series field opposes the shunt field, the generator is called differentially compound. Compound generators were designed to overcome the drop in terminal voltage which occurs in a shunt generator, when the load is increased. This voltage drop is undesirable where constant voltage loads such as lighting systems are used.

ALTERNATORS

The a.c. generator is the most important means for the production of electrical power. A.c. generators, or alternators, vary greatly in size depending on the power they are required to supply. Regardless of size, however, all electrical generators, whether d.c. or a.c., depend for their operation

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on the action of a coil cutting through a magnetic field, or of a magnetic field cutting through a coil. As long as there is relative motion between a conductor and a magnetic field, a voltage will be generated. In order that relative motion may take place between a conductor and a magnetic field, all generators are made up of two mechanical parts – a rotor and a stator.

It is known that in a d.c. generator the revolving part is always the armature. In an a.c. generator, however, this is not usually true. There are two types of alternators: the revolving-armature type and the revolving-field type.

The revolving-armature type alternator is similar in construction to the d.c. generator in that the armature rotates through a stationary magnetic field. But in the d.c. generator the e.m.f. generated in the armature windings is converted into d.c. by means of a commutator; whereas in the alternator the generated a.c. is brought to the load unchanged by means of slip rings. The revolving-armature alternator is only found in alternators of small power rating and is not generally used.

The revolving-field type of alternator has a stationary armature winding and a rotating field winding. The advantage of having a stationary armature winding is that the generated voltage can be connected directly to the load. Fixed connections are much more easily insulated than would be slip rings at very high voltages; so high-voltage alternators are usually of the rotating field type.

Since a major part of all electrical power generated is a.c., many motors are designed for a.c. operation. A.c. motors can, in most cases, duplicate the operation of d.c. motors and are less troublesome to operate. A.c. motors are particularly well-suited for constant-speed applications, since the speed is determined by the frequency of the a.c. applied to the motor terminals. A.c. motors are also made, however, which have variable speed characteristics within certain limits.

A.c motors can be designed to operate from a single-phase a.c. supply or from a multi-phase a.c. supply. Whether the motor is single-phase or multi-phase, it operates on the same principle. This principle is that the a.c. applied to the motor generates a rotating magnetic field, and this rotating field causes the rotor of the motor to turn.

A.c. motors are generally classified into two types: the synchronous motor and the induction motor. The synchronous motor is an alternator operated as a motor, in which a.c. is applied to the stator and d.c. is applied to the rotor. The induction motor differs from the synchronous motor in that it does not have its rotor connected to any source of power. Of the two types of a.c. motors mentioned, the induction motor is by far the most commonly used.

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REVISION TEST

Translate the following words into Russian:

Translate the following words into English:

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