Министерство образования и науки Хабаровского края
Краевое государственное бюджетное профессиональное образовательное учреждение
«Комсомольский-на-Амуре авиационно-технический техникум»
ПРАКТИЧЕСКОЕ ПОСОБИЕ
ПО ИНОСТРАННОМУ (АНГЛИЙСКОМУ) ЯЗЫКУ
Специальность 13.02.11 Техническая эксплуатация и обслуживание электрического и электромеханического оборудования (по отраслям)
Форма обучения (очная)
Курс 2, 3, 4 семестр 3, 4, 5, 6, 8
Практические занятия 172 часа
Самостоятельная работа 86 часов
Зачет 8 семестр
Учебное пособие составлено в соответствии с требованиями федерального государственного образовательного стандарта среднего профессионального образования, утвержденного приказом Министерства образования и науки Российской Федерации от «06» ноября 2009 г. № 247
Рассмотрено на заседании ПЦК общеобразовательных дисциплин
Протокол № ___ от «___» ___________ 2015 г.
Председатель ПЦК ___________ Н.К. Тургенева
(подпись) (ФИО)
Составитель преподаватель английского языка ___________ Т.Е. Марфина
(должность) (подпись) (ФИО)
2015
Аннотация
Предлагаемое учебное пособие предназначено для студентов 2-4 курса специальности 13.02.11 Техническая эксплуатация и обслуживание электрического и электромеханического оборудования (по отраслям) и разработано в соответствии с требованиями федерального государственного образовательного стандарта среднего профессионального образования и учебной программы курса английского языка.
Цель настоящего пособия – формирование навыков работы с иноязычными текстами, навыков перевода, извлечения информации и её переработки на основе различных видов чтения, расширение активного и пассивного словарного запаса в профессиональной области. Учебное пособие позволяет решать следующие задачи на уроке иностранного языка (английского):
- совершенствование процесса качественного произношения слов;
- введение и закрепление лексики;
- работа над грамматикой;
- совершенствование навыков устной речи.
Специальная лексика вводится тематически, закрепляется в разнообразных упражнениях. Разделы включают в себя следующие задания:
- прочитать и перевести текст;
- дать ответы на вопросы к тексту;
- заполнить пропуски подходящей по смыслу лексикой;
- составить монологические и диалогические высказывания по предлагаемым для обсуждения темам с обязательным использованием лексики урока.
Разработанные упражнения предназначены для организации адекватного понимания содержания текстов.
Материалы, представленные в пособии, могут использоваться как в ходе самостоятельной работы студентов над иностранным языком, так и на практических занятиях под руководством преподавателя.
Contents
Unit 1 4
Unit 2 5
Unit 3 6
Unit 4 8
Unit 5 10
Unit 6 11
Unit 7 12
Unit 8 14
Unit 9 15
Unit 10 16
Unit 11 17
Unit 12 18
Unit 13 19
Unit 14 21
Unit 15 23
Unit 16 24
Unit 17 25
Unit 18 26
Unit 19 28
Список использованных источников 30
UNIT 1
I. Read the text
THE NATURE OF ELECTRICITY
Practical electricity is produced by small atomic particles known as electrons. It is the movement of these particles which produce the effects of heat and light.
The pressure that forces these atomic particles to move, the effects they encounter opposition and how these forces are controlled are some of the principles of electricity.
Accepted atomic theory states that all matter is electrical in structure. Any object is largely composed of a combination of positive and negative particles of electricity. Electric current will pass through a wire, a body, or along a stream of water. It can be established in some substances more readily than in others, that all matter is composed of electric particles despite some basic differences in materials. The science of electricity then must begin with a study of the structure of matter. Matter is defined as any substance which has mass (or weight) and occupies space. This definition should be broad enough to cover all physical objects in the universe. Wood, water, iron, and paper are some examples of matter. Energy is closely related to, but not to be confused with, matter. Energy does not have mass, and it does not occupy space. Heat and light are examples of energy.
The smallest particle of matter which can be recognized as an original substance was thought to be a unit called the atom. Recently scientists have found particles even smaller than atoms, but our theories are still based on the atom. The atom consists of a nucleus and a cloud of electrons. It is generally agreed that the electrons are small particles of electricity, which are negative in nature. These particles orbit the nucleus in much the same fashion that planets orbit a sun.
II. Guess the meaning of the following international words:
Electricity, electron, effect, structure, combination, material, mass, energy, atom, orbit
III. Give the English equivalents for the words below:
1) производить; 2) частица; 3) тепло и свет; 4) напряжение; 5) сила; 6) вещество; 7) положительный; 
отрицательный; 9) электрический ток; 10) вес; 11) ядро
IV. Translate into Russian the words and expressions from the text:
1) atomic particle; 2) effects of heat and light; 3) encounter opposition; 4) principles of electricity; 5) composed (of); 6) pass through a wire; 7) structure of matter; occupy space; 9) physical objects; 10) a cloud of electrons; 11) in the same fashion.
V. Complete the sentences using the text:
1. Electricity is produced by …
2. The effects of heat and light are produced by …
3. According to the accepted atomic theory all matter is …
4. Any object is composed of …
5. Matter is defined as …
6. Energy must not be confused with …
7. The atom consists of …
8. The smallest particle of matter is …
9. Most theories are based on …
10. Electrons are …
VI. Answer the questions:
1) What are the principles of electricity? 2) What must the science of electricity begin with? 3) Are there any differences between energy and matter? What are they? 4) What is recognized as an original substance now?
VII. Topics for discussion:
1. The nature of electricity;
2. The nature of matter;
3. Contents of atomic theory.
UNIT 2
I. Read the text
ELECTRIC CURRENT
The electric current is a quantity of electrons flowing in a circuit per second of time. The unit of measure for current is ampere. If one coulomb passes a point in a circuit per second then the current strength is 1 ampere. The symbol for current is I.
The current which flows along wires consists of moving electrons. The electrons move along the circuit because the e .m. f. drives them. The current is directly proportional to the e. m. f.
In addition to traveling through solids, however, the electric current can flow through liquids as well and even through gases. In both cases it produces some most important effects to meet industrial requirements. Some liquids, such as melted metals for example, conduct current without any change to themselves. Others, called electrolytes, are found to change greatly when the current passes through them.
When the electrons flow in one direction only, the current is known to be d. c., that is, direct current. The simplest source of power for the direct current is a battery, for a battery pushes the electrons in the same direction all the time (i.e., from the negatively charged terminal to the positively charged terminal).
The letters a. c. stand for alternating current. The current under consideration flows first in one direction and then in the opposite one. The a. c. used for power and lighting purposes is assumed to go through 50 cycles in one second.
One of the great advantages of a. c. is the ease with which power at low voltage can be changed into an almost similar amount of power at high voltage and vice versa. Hence, on the one hand alternating voltage is increased when it is necessary for long-distance transmission and, on the other hand, one can decrease it to meet industrial requirements as well as to operate various devices at home.
Although there are numerous cases when d. c. is required, at least 90 per cent of electrical energy to be generated at present is a. c. In fact, it finds wide application for lighting, heating, industrial, and some other purposes.
II. Guess the meaning of the following international words:
electric, ampere, symbol, proportional, industrial, metal, electrolyte, battery, generate.
III. Give the English equivalents for the words and word combinations below:
a. 1) течь, протекать; 2) цепь, схема; 3) единица измерения; 4) провод; 5) электродвижущая сила; 6) твердое тело; 7) жидкость; проводить (ток); 9) источник энергии; 10) постоянный ток; 11) переменный ток; 12) напряжение.
IV. Give Russian equivalents for the following:
b. 1) to meet industrial requirements; 2) melted metals; 3) to push in the same direction; 4) negatively (positively) charged terminal; 5) power and lightning purposes; 6) long-distance transmission; 7) to operate devices; to find wide application.
V. Say whether these sentences are true or false:
1. The symbol for current is I.
2. The electric current can flow only through liquids.
3. The current can be of two types: direct current and alternating current.
4. The alternating current flows in one direction.
5. A battery is the simplest source of power for the direct current.
6. Direct current finds wider application than alternating current.
7. Electrolytes don’t change greatly when current passes through them.
8. One of the great advantages of alternating current is the ease with which voltage can be changed.
VI. Fill in the blanks, using the words from the box:
direct current, solids, conduct, electric current, liquids, voltage, alternating current
- A quantity of moving electrons flowing in a circuit is the a) _______ .
- The current can flow through b) ________ and c) ________ .
- Some liquids d) _______ current without any change to themselves.
- When the electrons flow in one direction only, the current is known to be e) _______ .
- The current flowing first in one direction and then in the opposite one is f) _______ .
- Such advantage of alternating current as alternating g) _______ finds wide industrial and household application.
VII. State the questions to the underlined words:
1. Melted metals conduct current without any change to themselves.
2. Alternating voltage can be changed to operate various devices at home.
3. A battery pushes the electrons in the same direction.
4. The alternating current is used for power and lightning purposes.
5. Alternating current accounts for 90 per cent of electrical energy generated now.
VIII. Say some sentences about the types of electric current and its properties
UNIT 3
I. Read the text
EFFECTS PRODUCED BY A CURRENT
The current flow is detected and measured by any of the effects that it produces. There are three important effects accompanying the motion of electric charges: the heating, the magnetic, and chemical effects, the latter is manifested under special conditions.
The production of heat is perhaps the most familiar among the principal effects of an electric current. The heating effect of the current is found to occur in the electric circuit itself. It is detected owing to an increase in the temperature of the circuit. This effect represents a continual transformation of electric energy into heat. For instance, the current which flows through the filament of an incandescent lamp heats that filament to a high temperature.
The heat produced per second depends both upon the resistance of the conductor and upon the amount of current carried through it. The thinner the wire is, the greater the developed heat is. On the contrary, the larger the wire is, the more negligible the heat produced is. Heat is greatly desirable at times but at other times it represents a waste of useful energy. It is this waste that is generally called «heat loss» for it serves no useful purposes and decreases efficiency.
The heat developed in the electric circuit is of great practical importance for heating, lighting and other purposes. Owing to it people are provided with a large number of appliances, such as: electric lamps that light our homes, streets and factories, electrical heaters that are widely used to meet industrial requirements, and a hundred and one other necessary and irreplaceable things which have been serving mankind for so many years.
The electric current can manifest itself in some other way. It is the motion of the electric charges that produces the magnetic forces. A conductor of any kind carrying an electric current, a magnetic field is set up about that conductor.
This effect exists always whenever an electric current flows, although in many cases it is so weak that one neglects it in dealing with the circuit. An electric charge at rest does not manifest any magnetic effect. The use of such a machine as the electric motor has become possible owing to the electromagnetic effect.
The last effect to be considered is the chemical one. The chemical effect is known to occur when an electric current flows through a liquid. Thanks to it a metal can be transferred from one part of the liquid to another. It may also effect chemical changes in the part of the circuit comprising the liquid and the two electrodes which are found in this liquid. Any of the above mentioned effects may be used for detecting and measuring current.
II. Give the English equivalents for the following words:
1. выявлять, обнаруживать; 6. лампа накаливания;
2. измерять; 7. прибор;
3. заряд; 8. потеря энергии;
4. нить накала; 9. освещать;
5. тепловой эффект; 10. обнаруживаться, проявляться.
III. Guess the meaning of the following international words:
transformation, temperature, chemical, magnetic, special, practical, motor, electrode.
IV. Insert words and expressions:
1. The current flow is (выявляется и измеряется) by any of the effects that it produces.
2. There are three important effects accompanying the motion of (электрические заряды).
3. The current which flows through the (нить накала лампы накаливания) heats that filament to a high temperature.
4. Heat represents (потерю полезной энергии) at times.
5. Electric lamps (освещать) our homes, streets and factories.
6. The electric current can (проявлять) magnetic effect.
V. Choose the correct translation:
The heating effect of the current is found to occur in the electric circuit itself.
1. Установлено, что тепловой эффект электрического тока обнаруживается в самой электрической цепи.
2. Тепловой эффект электрического тока может появляться в самой электрической цепи.
3. Установлено, что тепловой эффект электрического тока должен обнаруживаться в самой электрической цепи.
Когда в любом проводнике появляется электрический ток, вокруг него возникает магнитное поле.
1. A conductor of any kind carrying an electric current, a magnetic field was set up about that conductor.
2. A conductor of any kind have been carrying an electric current, a magnetic field is set up about that conductor.
3. A conductor of any kind carrying an electric current, a magnetic field is set up about that conductor.
Последний эффект, который необходимо рассмотреть – химический эффект.
1. The last effect is considered to be the chemical one.
2. The last effect to be considered is the chemical one.
3. The last effect would be considered the chemical one.
Известно, что химический эффект возникает, когда электрический ток проходит через жидкость.
1. The chemical effect is known to occur when an electric current flows through a liquid.
2. The chemical effect is famous to occur when an electric current flows through a liquid.
3. The chemical effect may be known to occur when an electric current flows through a liquid.
Именно движение электрических зарядов порождает магнитные силы.
1. The motion of the electric charges produces the magnetic forces.
2. It is the motion of the electric charges that produces the magnetic forces.
3. The motion of the electric charges is certain to produce the magnetic forces.
VI. Answer the questions:
1. What effects does the current flow produce?
2. How is the heating effect detected?
3. What does the heat produced depend upon?
4. What is called “heat loss”?
5. How is the magnetic effect set up?
6. What is the main condition of the magnetic effect existence?
7. When does the chemical effect occur?
VII. Speak about the principal effects of an electric current, using the text and chart above
UNIT 4
I. Read the text
ELECTRIC CURCUITS
The concepts of electric charge and potential are very important in the study of electric currents. When an extended conductor has different potentials at its ends, the free electrons of the conductor itself are caused to drift from one end to the other. The potential difference must be maintained by some electric source such as electrostatic generator or a battery or a direct current generator. The wire and the electric source together form an electric circuit, the electrons are drifting around it as long as the conducting path is maintained.
There are various kinds of electric circuits such as: open circuits, closed circuits, series circuits, parallel circuits and short circuits. To understand the difference between the following circuit connections is not difficult at all. If the circuit is broken or «opened» anywhere, the current is known to stop everywhere. The circuit is broken when an electric device is switched off. The path along which the electrons travel must be complete otherwise no electric power can be supplied from the source to the load. Thus the circuit is “closed” when an electric device is switched on.
When electrical devices are connected so that the current flows from one device to another, they are said «to be connected in series». Under such conditions the current flow is the same in all parts of the circuit as there is only a single path along which it may flow. The electrical bell circuit is considered to be a typical example of a series circuit. The “parallel” circuit provides two or more paths for the passage of current. The circuit is divided in such a way that part of the current flows through one path and part through another. The lamps in the houses are generally connected in parallel.
The “short” circuit is produced when the current can return to the source of supply without control. The short circuits often result from cable fault or wire fault. Under certain conditions the short circuit may cause fire because the current flows where it was not supposed to flow. If the current flow is too great a fuse is used as a safety device to stop the current flow.
II. Guess the meaning of the following international words:
concept, potential, electrostatic generator, aluminum, parallel, typical, control.
III. Give the English equivalents for the following words and word combinations:
1) электрические цепи, 2) электрический заряд, 3) проводник, 4) сопротивление, 5) движение электронов, 6) изолятор, 7) короткое замыкание, энергия.
IV. Say whether these sentences are true or false:
1. When an extended conductor has the same potential at its ends, free electrons are drifting from one end to another.
2. The wire and the electric source together form an electric circuit.
3. A path of any material will allow current to exist.
4. Silver, copper and gold oppose very strongly.
5. The slighter the opposition is, the better the insulator is.
6. There is only one type of electric circuit.
7. We close the circuit when we switch on our electric device.
V. Complete the sentences using the text:
1. The potential difference must be maintained by …
2. Materials that offer slight opposition are called …
3. The best insulators are …
4. There are various kinds of electric circuits such as …
5. We “open” the circuit when …
6. We “close” the circuit when …
7. The “short” circuit is produced when …
8. A fuse is …
VI. Answer the questions:
1. What concepts are very important in study of electric current?
2. What forms an electric circuit?
3. What materials are the best conductors and insulators?
4. What kinds of electric circuits do you know?
5. How can we open and close the circuit?
6. When are electrical devices connected in series?
7. What is an example of a series circuit?
8. What can you say about «parallel» circuits?
9. What does the short circuit often result from?
VII. Talk on the types of electric circuits
UNIT 5
I. Read the text
ALTERNATING CURRENT
Current is defined as increment of electrons. The unit for measuring current was named in honor of A.M. Ampere, the French physicist. Thus it is called ampere. The symbol for current is I. The electric current is a quantity of electrons flowing in a circuit per second of time. The electrons move along the circuit because the e. m. f. drives them. The current is directly proportional to the e. m. f.
A steam of electrons in a circuit will develop a magnetic field around the conductor along which the electrons are moving. The strength of the magnetic field depends upon the current strength along the conductor. The direction of the field is dependent upon the direction of the current.
If the force causing the electron flow is indirect, the current is called direct (d. c.). If the force changes its direction periodically the current is called alternative (a. c.).
Alternating current is the current that changes direction periodically. The electrons leave one terminal of the power supply, flow out along the conductor, stop, and then flow back toward the same terminal. A voltage that caused current reverses its polarity periodically. This is properly called an alternating voltage. The power supply that provides the alternating voltage actually reverses the polarity of its terminals according to a fixed periodic pattern. A given terminal will be negative for a specific period of time and drive electrons out through the circuit. Then, the same terminal becomes positive and attracts electrons back from the circuit. This voltage source cannot be a battery. It must consist of some types of rotating machinery.
II. Guess the meaning of the following international words:
1) physicist, 2) ampere, 3) symbol, 4) second, 5) polarity, 6) period, 7) battery.
III. Translate into Russian the words and expression from the text:
1) increment of electrons; 2) measuring; 3) to drive; 4) directly proportional; 5) conductor; 6) strength; 7) causing force; terminal; 9) to flow; 10) to reverse.
IV. Give the English equivalents for the words below:
1) переменный ток, 2) за секунду, 3) количество электронов, 4) поток электронов, 5) магнитное поле, 6) направление, 7) зависеть, усиление, 9) источник напряжения, 10) ротационный механизм.
V. Complete the sentences using the text:
1. The electric current is …
2. The unit for measuring current is …
3. A steam of electrons in a circuit will develop …
4. The current is called direct if …
5. The current is called alternating if…
6. Alternating voltage is …
7. Alternating voltage source cannot be …
VI. Answer the questions:
1. Why do electrons move along the circuit?
2. What does the strength of the magnetic field depend upon?
3. What does the direction of the field depend upon?
4. What is the way of alternating current electrons?
5. How does the alternating voltage power supply reverse the polarity of terminals?
VI. Talk on the properties of the electric current and its types
UNIT 6
I. Read 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 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.
II. 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; cord; 9) high voltage transmission line; 10) leak off.
III. Find in the text the sentences with the following related words and translate them:
conducting – conductor – conductivity – conductance
IV. State questions to the underlined words:
1) Solid metals conduct electricity with ease.
2) Conductance depends on the four factors.
3) There are many kinds of insulation used to cover the wires.
4) Insulators keep electricity from leaking off the conductor.
5) Conductors play an important role in electrical engineering.
V. Say whether these sentences are true or false:
1) Electrical conductivity of a body depends upon its atomic constitution.
2) There is no difference in the conducting ability of various substances.
3) The longer the wire is the weaker its opposition is.
4) The kind of the insulating material depends upon the purpose it is meant for.
5) Conductors are substances through which electricity is easily transmitted.
6) Insulators do not allow the electric current to flow freely.
VI. Talk on the conducting ability of various substances and their appliance in electrical engineering.
UNIT 7
I. Read the text
SEMICONDUCTORS
There are materials that really occupy a place between the conductors of the electric current and the non-conductors. They are called semiconductors. These materials conduct electricity less readily than conductors but much better than insulators.
Semiconductors include almost all minerals, many chemical elements, a great variety of chemical compounds, alloys of metals, and a number of organic compounds. Like metals, they conduct electricity but they do it less effectively.
In metals all electrons are free and in insulators they are fixed. In semiconductors electrons are fixed, too, but the connection is so weak that the heat motion of the atoms of a body easily pulls them away and sets them free.
Minerals and crystals appear to possess some unexpected properties. It is well known that their conductivity increases with heating and falls with cooling.
As a semiconductor is heated, free electrons in it increase in number, hence, its conductivity increases as well.
Heat is by no means the only phenomenon influencing semiconductors. They are sensitive to light, too. Take germanium as an example. Its electrical properties may greatly change when it is exposed to light. With the help of a ray of light directed at a semiconductor, we can start or stop various machines, effect remote control, and perform lots of other useful things. Just as they are influenced by falling light, semiconductors are also influenced by all radiation.
Generally speaking, they are so sensitive that a heated object can be detected by its radiation.
Such dependence of conductivity on heat and light has opened up great possibilities for various uses of semiconductors. The semiconductor devices are applied for transmission of signals, for automatic control of a variety of processes, for switching on engines, for the reproduction of sound, protection of high-voltage transmission lines, speeding up of some chemical reactions, and so on. On the one hand they may be used to transform light and heat energy directly into electric energy without any complex mechanism with moving parts, and on the other hand, they are capable of generating heat or cold from electricity.
Russian engineers and scientists turned their attention to semiconductors many years ago. They saw in them a means of solving an old engineering problem, namely, that of direct conversion of heat into electricity without boilers or machines. Semiconductor thermocouples created in Russia convert heat directly into electricity just as a complex system consisting of a steam boiler, a steam engine and a generator does it.
II. Give the English equivalents for the words and word combinations below:
1) полупроводник; 2) химическое соединение; 3) сплав; 4) освобождать; 5) свойство; 6) увеличивать(ся); 7) охлаждение; чувствительный к; 9) выставлять; 10) луч; 11) направлять на; 12) дистанционное управление; 13) находить, обнаруживать; 14) защита; 15) ускорение; 16) решить инженерную проблему; 17) термоэлемент.
III. Guess the meaning of the following international words:
element, organic, mineral, crystal, phenomenon, automatic, control, process, reproduction, conversion, boiler.
IV. Join the beginnings and ends:
-Semiconductors are sensitive to … conductors of the electric current and non-conductors.
-Semiconductors convert heat into … … dependence of conductivity on heat and light.
-Semiconductors occupy a place between… … heat and light.
-Semiconductors conduct electricity …into electricity without machines.
-As a semiconductor is heated … … its conductivity increases as well.
V. Insert words and expressions:
1) Semiconductors include a great variety of (химические соединения), (сплавы металлов).
2) Minerals and crystals appear to possess some unexpected (свойства). Their conductivity increases with (нагревание) and falls with (охлаждение).
3) With the help of a ray of light directed at a semiconductor, we can effect (дистанционное управление).
4) The semiconductor devices are applied for (автоматический контроль) of a variety of processes, for the (воспроизведение) of sound, (ускорение) of some chemical reactions.
5) (Термоэлементы) created in Russia convert heat directly into electricity.
VI. Answer the questions:
1) What do semiconductors include? 2) How does the atomic structure of semiconductors influence their properties? 3) What phenomena influence semiconductors? 4) What are the semiconductor devices applied for? 5) How do semiconductors help in solving engineering problems?
VII. Talk on the properties of semiconductors and their practical application
UNIT 8
I. Read the text
ELECTRICITY AND MAGNETISM
Text 1. Electromotive force
When free electrons are dislodged from atoms, electrical energy is released.
Chemical reaction, friction heat and electromagnetic induction will cause electrons to move from one atom to another. Whenever energy in any form is released, a force called electromotive (e. m. f.) is developed. If the force exerts its effort always in one direction, it is called direct; and if the force changes its direction of exertion periodically, it is called alternating.
The chemical reaction in a dry cell, heat and friction are sources of a unidirectional force. Electromagnetic induction produces an alternating force. The direction of force depends on the direction in which the field is cut. Whenever an e. m. f. is developed, there is also a field of energy called an electrostatic field, which can be detected by an electroscope and measured by an electrometer.
Text 2 Electromagnetic Induction
An electromotive force is induced in the conductor when there is a change in the magnetic field surrounding a conductor. This induced electromotive force may be produced in several ways as follows:
a. A conductor may move in a stationary magnetic field of constant strength.
b. A stationary conductor may be exposed ‘to a moving magnetic field of constant strength.
c. The strength of the field surrounding the conductor may change without any motion of conductor or magnetic circuit.
The electromotive force induced by motion of a conductor or a magnetic flux is the same when the conductor rotates and the flux is stationary or the flux rotates and the conductor is stationary. If both, conductor and flux, rotate in the same direction at the same speed, no electromotive force will be produced, if they rotate at the same speed but in opposite directions, the electromotive force induced would be twice as that which would be induced, if one of them was stationary. An electromotive force is not induced when a conductor is moved parallel to the lines of force, but only when it moves at an angle with these lines.
Any motion across the direction of the lines, however, will produce an electromotive force in the conductor. For this reason, the conductor is said to «cut» the lines of force. The actual electromotive force induced in the conductor depends upon the nature at which the flux is cut.
Text 3 Electromotive force and resistance
The electromotive force is the very force that moves the electrons from one point in an electric circuit towards another. In case this e. m. f. is direct, the current is direct. On the other hand, were the electromotive force alternating, the current would be alternating, too. The e. m. f. is measurable and it is the volt that is the unit used for measuring it. A current is unable to flow in a circuit consisting of metallic wires alone. A source of an e. m. f. should be provided as well. The source under consideration may be a cell or a battery, a generator, a thermocouple or a photocell, etc.
In addition to the electromotive force and the potential difference reference should be made to another important factor that greatly influences electrical flow, namely, resistance. All substances offer a certain amount of opposition, that is to say resistance, to the passage of current. This resistance may be high or low depending on the type of circuit and the material employed. Glass and rubber offer a very high resistance and, hence, they are considered as good insulators. All substances do allow the passage of some current provided the potential difference is high enough.
Certain factors can greatly influence the resistance of an electric circuit.
They are the size of the wire, its length, and type. In short, the thinner or longer the wire, the greater is the resistance offered.
II. Give the English equivalents for the words below. Find in the text the sentences with these words and translate them
1) трение; 2) электродвижущая сила; 3) элемент; 4) параллельное соединение; 5) сопротивление; 6) электромагнитная индукция; 7) переменный ток; постоянное напряжение; 9) фотоэлемент.
III. Guess the meaning of the following international words and translate them:
reaction, electrostatic, electrometer, electroscope, volt, metallic.
IV. Say whether these sentences are true or false:
1. Alternating force always exerts its effort in one direction.
2. Alternating force is produced by electromagnetic induction.
3. The electromotive force is induced by motion of a conductor.
4. Resistance is an important factor that greatly influences electrical flow.
5. The type of the material employed doesn’t influence the resistance.
V. Answer the questions:
1) What factors cause the motion of electrons from one atom to another? 2) When is the electromotive force developed? 3) When does an electrostatic field appear? 4) How is the electromotive force induced? 5) What unit is used for measuring the electromotive force? 6) What are the sources of electromotive force? 7) What is called “resistance”? How do the types of circuit and material influence the resistance? 9) Name the factors that influence the resistance.
UNIT 9
I. Read the text
DYNAMOS
The term «dynamo» is applied to machines which convert either mechanical energy into electrical energy or electrical energy into mechanical energy by utilizing the principle of electromagnetic induction. A dynamo is called a generator when mechanical energy supplied in the form of rotation is converted into electrical energy. When the energy conversion takes place in the reverse order the dynamo is called a motor. Thus a dynamo is a reversible machine capable of operation as a generator or motor as desired.
A generator does not create electricity, but generates or produces an induced electromotive force, which causes a current to flow through a properly insulated system of electrical conductors external to it. The amount of electricity obtainable from such a generator is dependent upon the mechanical energy supplied. In the circuit external to a generator the e. m. f. causes the electricity to flow from a higher or positive potential to a lower or negative potential. In the internal circuit of a generator the e. m. f. causes the current to flow from a lower potential to a higher potential. The action of a generator is based upon the principles of electromagnetic induction.
The dynamo consists essentially of two parts: a magnetic field, produced by electromagnets, and a number of loops or coils of wire wound upon an iron core, forming the armature. These parts are arranged so that the number of the magnetic lines of force of the field threading through the armature, coils will be constantly varied, thereby producing a steady e. m. f. in the generator or a constant torque in the motor.
II. Fill in the gaps with the words given below:
to convert, generator, reversible, obtainable, induction, loops
1. The term “dynamo” is applied to machines which…..either mechanical energy into electrical or on the contrary electrical energy into mechanical energy.
2. A dynamo is a ….. machine capable of operation as a generator or motor as desired.
3. The amount of electricity ….. from such a generator is dependent upon the mechanical energy supplied .
4. The action of a generator is based upon the principles of electromagnetic …… .
5. The dynamo consists of two parts: a magnetic field, produced by electromagnets, and a number of …..or coils of wire.
III. Find the Russian equivalents for the following English words and word combinations:
1) to be applied to smth.; 2) to convert smth. into smth.; 3) rotation; 4) to utilize; 5) a properly insulated system; 6) internal (external) circuit; 7) capable of operation; positive (negative) potential; 9) reverse order; 10) energy conversion.
IV. Answer the questions
1. What term can be applied to machines converting mechanical energy into electrical?
2. What kind of machine is a dynamo?
3. What is the function of a generator?
4. What is the action of a generator based upon?
5. What parts does the dynamo consist of?
UNIT 10
I. Read the text
GENERATORS
The powerful, highly efficient generators and alternators that are in use today operate on the same principle as the dynamo invented by the great English scientist Faraday in 1831. Dynamo-electric machines are used to supply light, heat and power on a large scale. These are the machines that produce more than 99.99 per cent of all the world’s electric power.
There are two types of dynamos – the generator and the alternator. The former supplies d. c. which is similar to the current from a battery and the latter provides a. c. 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.
A generator is an electric machine, which converts mechanical energy into electric energy. There are direct-current (d. c.) generators and alternating current (a. c.) generators. Their construction is much alike. A d. c. generator consists of stationary and rotating elements. The stationary elements are: the yoke or the frame and the field structure. The yoke forms the closed circuit for the magnetic flux. The function of the magnetic structure is to produce the magnetic field.
The rotating elements are: true armature and the commutator. They are on the same shaft. The armature consists of the core and the winding. The winding is connected to the commutator. With the help of the brushes on the commutator that conduct the electric current to the line the winding is connected to the external circuit. The stationary element of an a. c. generator is called a stator. The rotating element is called a rotor. The essential difference between a d. c. generator and a. c. generator is that the former has a commutator by means of which the generated e. m. f. is made continuous, i. e. the commutator mechanically rectifies the alternating e. m. f. so that it is always of the same polarity.
D. c. generators are used for electrolytic processes such as electroplating. Large d. c. generators are employed in such manufacturing processes as steel making. The d. c. generator of small capacities is used for various special purposes such as arc welding, automobile generators, train lighting systems, etc. It also finds rather extensive use in connection with communication systems.
II. Give the Russian equivalents for the following English words and word combinations:
1) generator; 2) alternator; 3) steam turbine; 4) water turbine; 5) armature; 6) rotor; 7) stationary; commutator; 9) stator; 10) yoke; 11) brushes; 12) core; 13) frame; 14) winding.
III. Fill in the blanks
1. A generator is an electric machine, which a) —— mechanical energy into electrical energy.
2. A direct-current generator consists of b) —— .
3. The dynamo was invented by c) —— in 1831.
4. The d.c. generator is used for various purposes such as d) —— .
IV. Work out the plan of the text
V. Speak on the following points:
1. The construction of a generator.
2. The direct current generators and their industrial application.
UNIT 11
I. Read the text
MAIN STRUCTURAL ELEMENTS OF A D. C. MACHINE
A direct-current machine consists of two main parts, a stationary part, usually called the stator, designed mainly for producing a magnetic flux, and a rotating part, called the armature or the rotor. The stationary and rotating parts should be separated from each other by an air-gap. The stationary part of a d. c. machine consists of main poles, designed to create the main magnetic flux; commutating poles interposed between the main poles; and a frame. It should be noted here that sparkles operation of the machine would be impossible without the commutating poles. Thus, they should ensure sparkles operation of the brushes at the commutator.
The main pole consists of a laminated core the end of which facing the armature carries a pole shoe and a field coil through which direct current passes. The armature is a cylindrical body rotating in the space between the poles and comprising a slotted armature core, a winding inserted in the armature slots, a commutator, and a brush gear.
The frame is the stationary part of the machine to which are fixed the main and commutating poles and by means of which the machine is bolted to its bedplate. The ring shaped portion which serves as the path for the main and commutating pole fluxes is called the yoke. End-shields or frame-heads which carry the bearings are also attached to the frame. Of these main structural elements of the machine the yoke, the pole cores, the armature core and the air-gap between the armature core and the pole core are known to form the magnetic circuit while the pole coils, the armature windings, the commutator and brushes should form the electric circuit of the machine.
II. Translate the following phrases, using the given variants of translation:
to consist – состоять : to consist of a stationary part and a rotating part;
separated – отдельный изолированный: the stationary and rotating parts should be separated from each other by an air gap;
to serve – служить в качестве чего-либо: the ring shaped portion or yoke
serves as a path for the main and commutating pole fluxes.
III. Arrange synonyms in pairs and memorize them:
a) to consist of; to be separated from; to create; to be interposed between; to pass; to rotate;
в) to be divided with; to produce; to introduce into; to permeate; to roll; to revolve; to comprise.
IV. Write out the names of the machine parts and describe their operational characteristics
UNIT 12
I. Read the text
THE ALTERNATOR
The alternator is an electric machine for generating an alternating current by a relative motion of conductors and a magnetic field. The machine usually has a rotating field and a stationary armature. In a synchronous alternator the magnetic field is excited with a direct current. The direction of an induced e. m. f. is reversed each time when a conductor passes from a pole of one polarity to a pole at another polarity. Most machines of this type are used for lighting and power, but there are alternators with a revoking armature and a stationary field. They are used in small sizes mostly for special purposes.
Any electrical machine is reversible. When a machine is driven by a source of mechanical power, it works as a generator and delivers electrical power. If it is connected to a source of electrical power, it produces mechanical energy, and operates as a motor. The alternator may also be operated as a motor.
The a-c .generator, or alternator, does not differ in principle from the d. c. generator. The alternator consists of a field structure and an armature. The field structure is magnetized by a field winding carrying a .direct current. An electromotive force is generated in tine winding of the armature. In alternators the field is usually the rotating element and the armature is stationary. This construction has a number of advantages. Only two rings are needed with a rotating field. These rings carry only a relatively light field current, at a voltage generally of 125, and seldom exceeding 250. The insulation of such rings is not difficult. A stationary armature requires no slip rings. The leads from the armature can be continuously insulated from the armature winding to the switchboard, leaving no bare conductor. The alternator with a rotating field may be further divided into the vertical and the horizontal types.
The vertical type is usually applied for large water-wheel generators where it is desirable to mount the water turbine below the generator. The more common horizontal type is used with diesel and steam engine drive. A low speed alternator of this type is suitable for a diesel engine drive, a high speed alternator is suitable for a steam turbine drive.
II. Form nouns, denoting devices with the help of the suffix – or. Translate them
To alternate, to commute, to conduct, to generate
III. Read the text and write out the key words, characterizing the alternator
IV. Translate the following word combinations paying attention to the Participle 2
The leads from the armature can be continuously insulated from….., the vertical type of alternator applied for large water-wheel generator; alternators with a revoking armature and a stationary field used in small sizes mostly for special purposes; a machine driven by a source of mechanical power; the direction of an induced e. m. f. …
V. State 5 questions to the text
VI. Points for discussion:
1. The structure of the alternator;
2. The application of the alternator.
UNIT 13
I. Read the text
THE INDUCTION MOTOR
An induction motor like any other motor consists of a stationary part, the stator, and a rotating part, the rotor. The rotor of an induction motor is not connected electrically to the source of power supply. The currents which circulate in the rotor conductors are the result of voltage induced in the rotor in the magnetic field set up by the stator. The rotor is fitted with a set of conductors in which currants flow. As these conductors lie in the magnetic field produced by the stator, a force is exerted on the conductors and the rotor begins to revolve. The operation of the motor depends upon the production of a rotating magnetic field. The speed at which the field of an induction motor turns is called the synchronous speed of the field or of the motor.
The induction motor is the simplest of the various types of electric motors and it has found more extensive application in industry than any other type. It is made in two forms – the squirrel cage and the wound rotor, the difference being in the construction of the rotor.
The stator of the induction motor has practically the same slot and winding arrangement as the alternator and has the coils arranged to form a definite number of poles, the number of poles being a determining factor in connection with the speed at which the motor will operate. The rotor construction, however, is entirely different.
The squirrel-cage rotor is a simpler form and has been used in many machines.
Instead of coils the winding consists of heavy copper bars.
The wound-rotor type has a winding made up of well-insulated coils, mounted in groups whose end connections are brought out to fill in rings. The purpose of this winding is to provide for variation in the amount of resistance included in the rotor circuit.
Provision for ventilation is made by leaving passageways through the core and frame, through which air is forced by fan vanes mounted on the rotor. In main cases the motors now built in as an integral part of the machine it is to drive.
There being no electrical connection between the rotor circuits of the induction motor and the stator circuits, or supply line, the currents which flow in the rotor bars or windings correspond to the induced voltages, the action being similar to that of a transformer with a movable secondary. With but a single phase winding on the stator, however, the torques produced in the two halves of the rotor would be in apposition, and the motor would not start. With more than one set of windings two for a two-phase motor, three for a three-phase motor a resultant field is produced which has the effect of cutting across the rotor conductors and induces voltages in them. This field is considered to be revolving at uniform speed.
The term “revolving field” should not be taken to mean actual revolution of flux lines. The magnetic field from the coils of each phase varies in strength with changes in current value but does not move around the stator. The revolutions are those of the resultant of the three, or two, phases, as the case may be.
A motor with a single-phase winding is not self-starting but must be provided with an auxiliary device of some kind to enable the motor to develop a starting torque. The effect of the revolving field is the same as would result from actual revolution of a stator having direct-current poles. As voltages have been induced in the bars or windings of the rotor, currants start flowing as a result of these voltages, and a torque is produced which brings the motor up to speed.
II. Find in the text the English equivalents for the word combinations given below:
1) асинхронный двигатель; 2) неподвижная часть; 3) вращающаяся часть; 4) проводник; 5) одновременная скорость; 6) широкое применение; 7) паз; механизм обмотки; 9) трансформатор; 10) вращающий момент.
III. Complete the following sentences according to the contents of the text
1. The Induction Motor is …….. of electric motors and is more extensively applied in industry than any other type.
2. The purpose of this winding is …….. for variation in the amount of resistance included in the rotor circuit.
3. The effect of …. is the same as would result from actual revolution of a stator having direct-current poles.
IV. Answer the following questions:
1. What parts does the induction motor consist of?
2. What are the names of its rotating and stationary parts?
3. What does the motor operation depend on?
4. How can the difference between stator and rotor construction be explained?
5. What does the term “revolving field” mean?
V. Translate the sentences from the text paying attention to the Participle Constructions:
1. The induction motor is made in two forms – the squirrel cage and the wound rotor, the difference being in the construction of the rotor.
2. The stator of the induction motor has practically the same slot and winding arrangement as the alternator and has the coils arranged to form a definite number of poles, the number of poles being a determining factor in connection with the speed at which the motor will operate.
3. There being no electrical connection between the rotor circuits of the induction motor and the stator circuits, or supply line, the currents which flow in the rotor bars or windings correspond to the induced voltages, the action being similar to that of a transformer with a movable secondary.
VI. Discuss the following points:
1) The construction of an induction motor;
2) Induction motor operation principle.
UNIT 14
I. Read the text
TYPES OF INDUCTION MOTORS
Text 1 Single-Phase Motor
The single-phase induction motor differs from poly-phase type principally in the character of its magnetic field, as an ordinary single-phase winding will not produce a rotating field, but a field that is oscillating, and the induced currents and poles produced in the rotor by this field will tend to produce equal torque in opposite directions, therefore, the rotor cannot start to revolve. However, if the rotor can in some manner be made to rotate at a speed corresponding to the frequency of the current in the stator windings then the reaction of the stator and rotor flux is such as to produce a torque that will keep the rotor revolving.
In practice the starting of single-phase induction motors is accomplished by three general methods applicable to small-sized motors only.
First: the split-phase method, in which an auxiliary stator winding is provided for starting purposes only, this winding being displaced from the main stator winding by 90 electrical degrees. It has a higher inductance than the main stator winding, thus causing the currant in it to lag far enough behind the current in the main winding to produce a shifting or rotating field during the starting period, which exerts a starting torque on the rotor sufficient to cause rotation.
When nearly normal speed has been reached the auxiliary winding is out of circuit by a switch and clutch in the motor, which operates automatically by centrifugal force, and the rotor continues to run as a single-phase motor. The starting torque of such motions being limited, they are frequently constructed with the rotor arranged to revolve freely on the shaft at starting until nearly normal speed is reached, at which time the load is pitched up by the automatic action of a centrifugal clutch.
Second: an auxiliary winding may be connected to the single-phase line through an external inductance and a switch (for disconnecting the auxiliary winding from the circuit after the motor has reached normal speed), the introduction of the inductance in the auxiliary winding splitting the phase as before.
Text 2 Three-Phase Induction Motor
The three-phase induction motor is the most commonly used type. It has been widely used in recent years. Normally an induction motor consists of a cylindrical core (the stator) which carries the primary coils in slots on its inner periphery. The primary coils are arranged for a three-phase supply and serve to produce a revolving magnetic field. The stator encircles a cylindrical rotor carrying the secondary winding in slots on its outer periphery. The rotor winding may be one of two types: squirrel-cage and slip-ring for wound-rotor). In a squirrel-cage machine the rotor winding forms a complete closed circuit in itself. The rotor winding of a slip-ring machine is completed when the slip rings are connected either directly together or through some resistance external to the machine. The rotor shaft is coupled to the shaft of the driven mechanism.
The rotor is stationary at some instant of time. The revolving magnetic field of the stator winding cuts across the stationary rotor winding at synchronous speed and induces an e. m. f. in it. The e. m. f. will give rise to a current which sets up a magnetic field. The rotor starts rotating.
It is the interaction between the rotor current and the revolving magnetic field that has created torque and has caused the rotor to rotate in the same direction as the revolving magnetic field. Tine speed of the rotor is 98–95 per cent of the synchronous speed of the revolving magnetic field of the stator.
Hence another name for this type of motor is the asynchronous motor. As a matter of fact, the speed of the rotor cannot be equal to synchronous speed. If it were equal to the latter, the revolving magnetic field would not be able to cut the secondary conductors and there would not be any current induced in the secondary winding and no interaction between the revolving field and the rotor current, and the motor would not run.
II. Translate the sentences, paying attention to the translation of the word -one-
1. One should distinguish between single-phase and three-phase induction motors.
2. The new device is better the old one.
3. The three-phase induction motor type is the most commonly used one.
4. The rotor winding may be one of two types.
5. As a matter of fact the speed of the rotor cannot be equal to synchronous one.
III. Translate the sentences from the text paying attention to the Participle Constructions:
1. In the split-phase method an auxiliary stator winding is provided for starting purposes only, this winding being displaced from the main stator winding by 90 electrical degrees.
2. The starting torque of such motions being limited, they are frequently constructed with the rotor arranged to revolve freely on the shaft at starting until nearly normal speed is reached.
3. An auxiliary winding may be connected to the single-phase line through an external inductance and a switch, the introduction of the inductance in the auxiliary winding splitting the phase as before.
IV. Answer the following questions:
1. What way does the single-phase motor differ from the three-phase one?
2. What is the starting of single-phase induction motors accomplished by?
3. How can an auxiliary winding be connected to the single-phase line?
4. What parts does an induction motor consist of?
5. What are the two types of the rotor winding?
V. Work out the plan of the text
VI. State 5 questions to the text
UNIT 15
I. Read the text
TRANSFORMERS
One of the great advantages in the use of the alternating current is the ease with which the voltage may be changed by means of a relatively simple device known as a transformer. Although there are many different types of transformers and a great variety of different applications, the principles of action are the same in each case.
The transformer is a device for changing the electric current from one voltage to another. It is used for increasing or decreasing voltage. So the function of a transformer is to change voltage and current of an alternating system to meet requirements of the equipment used. It is known to be simple in elementary principle, and in construction that is it involves no moving parts.
Transformers change voltage through electromagnetic induction.
The principle parts of a transformer are: an iron core and, usually, two coils of insulated windings. One of them is called primary, another is called the secondary. The primary coil is connected to the source of power. The secondary coil is connected to the load. Thus, the primary is the coil to which power is supplied. The secondary is the coil from which power is taken. In scientific terms to produce an alternating magnetic flux in the iron core an alternating current must be passed through the primary coil. This flux is considered to induce electromotive force in both primary and secondary coils. The secondary coil is open – circuited. Current flows in the secondary coil when the latter is connected to the external circuit or load. The flow of current in the secondary coil tends to reduce the flux in the core. Transformers are placed inside a steel tank usually with oil to improve the insulation and also to cool the device.
II. Guess the meaning of the following international words:
1) transformer; 2) type; 3) principle; 4) electric; 5) function; 6) elementary; 7) construction; induction.
III. Translate into Russian the words and expressions from the text:
1) advantage; 2) voltage; 3) relatively simple; 4) application; 5) increase; 6) to decrease; 7) to meet requirements; moving parts; 9) iron core; 10) insulated windings; 11) load; 12) electromotive force; 13) to induce.
IV. Give the English equivalents to the words below:
1) переменный ток; 2) прибор; 3) принцип работы (действия); 4) электромагнитная индукция; 5) катушка; 6) первичная (вторичная) обмотка; 7) источник питания; магнитный поток; 9) стальной контейнер; 10) остужать.
V. State questions to the underlined words:
1. Voltage may be changed by a transformer.
2. Transformers change voltage through electromagnetic induction.
3. Transformer is used for increasing or decreasing voltage.
4. The primary winding is connected to the source of power.
5. Transformers are placed inside a steel tank.
VI. Answer the questions:
1. What kind of device is a transformer?
2. What are the functions of a transformer?
3. What are the principle parts of a transformer?
4. What is the primary coil connected to?
5. What is the secondary coil connected to?
6. What are the principles of action of a transformer?
7. Where are transformers usually placed?
VI. Topics for discussion:
1. Transformer as an electric device;
2. Main parts and principles of a transformer action.
UNIT 16
I. Read the text
TYPES OF TRANSFORMERS
There are different types of transformers. By the purpose they are classified into step-up transformers and step-down transformers. In a step-up transformer the output voltage is larger than the input voltage, because the number of turns on the secondary winding is greater than that of the primary. In a step down transformer the output voltage is less than input voltage as the number of turns on the secondary is fewer than that on the primary.
By the construction transformers are classified into core-type and shell type transformers. In the core-type transformers the primary and the secondary coils surround the core. In the shell type transformers the iron core surrounds the coils. Electrically they are equivalent. The difference is in the mechanical construction.
By the methods of cooling transformers are classified into air – cooled, oil – cooled and water – cooled transformers.
By the number of phases transformers are divided into single – phase and polyphase transformers.
Instrument transformers are of two types, current and potential.
A current transformer is an instrument transformer used for the transformation of a current at a high voltage into proportionate current at a low voltage.
Current transformers are used in conjunction with a.-c. meters or instruments where the current to be measured must be of low value. They are also used where high – voltage current has to be metered. A voltage transformer, which is also called a potential transformer, may be defined as an instrument transformer for the transformation of voltage from one value to another. This transformer is usually of a step – down type because it is used when a meter is installed for use on a high – voltage system.
Transformers operate equally well to increase the voltage and to reduce it.
The above process needs a negligible quantity of power.
Transformers are widely used in our everyday life. 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.
II. Guess the meaning of the following international words:
1) to classify; 2) method; 3) phase; 4) instrument; 5) system; 6) process; 7) radio; television.
III. Give the English equivalents for the words below:
1) цель; 2) повышающий / понижающий трансформатор; 3) выходящее / входящее напряжение; 4) число витков; 5) механическое устройство; 6) монофазные / полифазные трансформаторы; 7) высокое / низкое напряжение; определять; 9) работать; 10) незначительное количество.
IV. Translate into Russian the words and expression from the text:
1) core-type / shell-type transformers; 2) air-cooled / oil – cooled / water – cooled transformers; 3) current / potential transformers; 4) in conjunction with smth.; 5) to reduce; 6) electronic equipment.
V. Complete the sentences using the text:
1. By the purpose transformers are …
2. By the construction transformers are …
3. By the methods of cooling transformers are …
4. By the number of phases transformers are …
5. Transformers operate equally well…
6. Process of voltage changing needs…
7. Familiar examples of transformer applications are …
VI. Answer the questions:
1. What voltage is larger in a step-up transformer and why?
2. What voltage is less in a step – down transformer and why?
3. What is the construction of a core – type transformer?
4. What is the construction of a shell – type transformer?
5. What are the two types of instrument transformers?
6. What are current transformers used for?
7. What are potential transformers used for?
VI. Topics for discussion:
1. Types of transformers;
2. Use of transformers in everyday life.
UNIT 17
I. Read the text
MEASUREMENTS OF ELECTRIC VALUES
The measurement of any physical quantity applies a determination of its magnitude in terms of some appropriate unit. In the case of simple fundamental quantities such as length, mass or time, the units themselves are simple.
Electrical and magnetic quantities are, however, much less simple than length, mass or time and cannot be measured directly by comparison with a material stand. The units in which these quantities are expressed have to be defined in terms of their observable affects obtained in experimental work, e.g. the weight of silver deposited in one second by a current when it is passed through a solution of silver nitrate is a measure of the magnitude of this current.
Electrical measurements can be classified broadly as neither absolute measurements, nor secondary measurements, but the first class of such measurements is rarely undertaken.
II. Guess the meaning of the following international words:
1) physical; 2) system; 3) fundamental; 4) material; 5) experimental; 6) absolute; 7) class.
III. Give the English equivalents to the words below:
1) измерение; 2) определение; 3) соответствующая единица; 4) быть соответствующим; 5) сравнение; 6) достигать; 7) серебро; широко; 9) заботиться; 10) длина.
IV. Translate into Russian the words and expressions from the text:
1) magnitude; 2) electrical and magnetic quantities; 3) to define; 4) observable affects; 5) to deposit; 6) secondary measurements; 7) to undertake.
V. Insert the words:
1. Magnitude of any … (физическая величина) must be determined in terms of some appropriate … (единица).
2. … (единицы) are simple for simple … (основных) quantities.
3. … (электрические) and (магнитные) quantities cannot be measured simply.
4. These units must be … (определены) in terms of their … (наблюдаемые) effects obtained in… (экспериментальная работа).
5. Absolute … (измерения) are … (редко) undertaken.
VI. Answer the questions:
1. What do we need to measure any physical quantity?
2. What simple units for measuring of simple fundamental quantities do you know?
3. Can electrical and magnetic quantities be measured directly by comparison with a material stand?
4. How can we get units for defining electrical and magnetic quantities?
5. What types of measurement do you know?
VII. State questions to the underlined words:
1. Before we can measure, we must decide upon a system of units.
2. Electric and magnetic quantities are much less simple than fundamental quantities.
3. These quantities cannot be measured directly by comparison with a material stand.
4. Electrical measurements can be classified as neither absolute, nor secondary measurements. (Question-tag)
VIII. Topics for discussion:
1. Measurement of any physical quantity;
2. Measurement of electric and magnetic quantities.
UNIT 18
I. Read the text
MAIN TYPES OF AMMETERS AND VOLTMETERS
Ammeters and voltmeters are made to operate on the same principle. The two principle kinds are the moving coil and moving iron types.
The electro-magnetic effect of the current is the one chiefly made use of for measuring purposes. Moving iron instruments employ this effect. The moving- iron instrument consists of a fixed coil of wire carrying the current which magnetizes a small piece of soft iron mounted on the instrument spindle. In construction there are two varieties: the repulsion type having two pieces of iron; and the attraction type having only one.
In the attraction type of the instrument the bobbin carrying the wire is oblong instead of circular, and has only a narrow slot-shaped opening in the center.
A thin flat piece of iron, which is mounted on the instrument spindle, is sucked into this opening by magnetic attraction when the current flows. Either gravity or spring control can be used on moving-iron instruments and damping is usually by means of an air-dash-pot.
A moving-coil instrument may be compared to a miniature direct-current motor in which the armature never moves more than about a quarter of a revolution.
When a current flows through the coil of a moving-coil type ammeter, it becomes a magnet, one face being of north, and the other of south polarity.
These poles are attracted by the poles of opposite polarity of the permanent magnet, and the coil tends to turn until its axis is parallel with the line joining the pole pieces of the permanent magnet. This movement is proportional to the current flowing and is opposed by the control springs. A pointer fixed to the coils moves over a graduated scale and indicates the current flowing in amperes. The scale of this type of instrument is evenly divided, but the positive terminal must be connected to the positive terminal of the supply or the instrument tends to read backward. Such an instrument is only suitable for d. c. circuits.
Moving-coil instruments are more accurate and sensitive, but more expensive than those of moving-iron types.
II. Give the English equivalents for the following words and word combinations:
1) электромагнитный тип; 2) магнитно-электрический тип; 3) ось; 4) репульсионный тип; 5) притягивающий тип; 6) продолговатый; 7) устанавливать; втягивать; 9) воздушный успокоитель.
III. Translate into Russian:
1) purpose; 2) employ; 3) slot-shaped; 4) magnetic attraction; 5) damp; 6) revolution; 7) pole; axis; 9) pointer; 10) graduated scale.
IV. Answer the questions:
1. What are the two principle kinds of ammeters and voltmeters?
2. What is the construction of a moving iron instrument?
3. What are the two types of moving iron instrument?
4. How does a moving coil instrument work?
5. What instrument is suitable only for d.c.?
6. What instruments are more expensive and sensitive: moving coil or moving iron instruments?
V. Insert the words:
1. In the attraction type of the … (механизмы) the bobbing is … (продолговатый) instead of … (круглый).
2. A small piece of … (железо) is mounted on the instrument … (ось).
3. … (Амортизация) is usually by means of an … (воздушный успокоитель)
4. The … (якорь) never moves more than about a quarter of a … (полный оборот) in a miniature d. c. motor.
5. … (катушечный) movement is proportional to … (движение тока) and is opposed by the … (пружинный механизм).
6. … (Стрелка) indicates the … (ток) flowing in … (ампер).
7. The … (положительный) terminal must be connected to the … (положительный) terminal of the … (питание) or the … (механизм) tends to read … (наоборот).
VI. Topics for discussion:
1. Moving iron instruments;
2. Moving coil instruments.
UNIT 19
I. Read the text
ELECTRICAL MEASURING INSTRUMENTS AND UNITS
Any instrument which measures electrical values is called a meter. An ammeter measures the current in amperes. The abbreviation for the ampere is amp. A voltmeter measures the voltage and the potential difference in volts.
The current in a conductor is determined by two things – the voltage across the conductor and the resistance of the conductor. The unit by which resistance is measured is called the ohm. The resistance in practice is measured with the ohm-meter. A wattmeter measures electrical power in watts. Very delicate ammeters are often used for measuring very small currents. A meter whose scale is calibrated to read a thousandth of an ampere is called a micro ammeter or galvanometer.
Whenever an ammeter or voltmeter is connected to a circuit to measure electric current or potential difference, the ammeter must be connected in series and the voltmeter in parallel. To prevent a change in the electric current when making such an insertion, all ammeters must have a low resistance. Hence, most ammeters have a low resistance wire, called a shunt, connected across the armature coil.
A voltmeter, on the other hand, is connected across that part of the circuit for which a measurement of the potential difference is required. In order that the connection of the voltmeter to the circuit does not change tire electric current in the circuit, the voltmeter must have high resistance. If the armature coil does not have large resistance of its own, additional resistance is added in series.
The heating effect, electrostatic effect, magnetic and electromagnetic effects of electric current are used in order to produce the defleting torque. The resulting measuring instruments are called: (a) hot wire, (b) electrostatic, (c) moving iron, (d) moving coil, and (e) induction. Various types are used with both d. c. and a. c., but the permanent-magnet moving coil instrument are used only with d. c., and the induction type instruments are limited to a. c.
All, except the electrostatic type instruments, are current measuring devices, fundamentally ammeters. Consequently, most voltmeters are ammeters designed also to measure small values of current directly proportional to voltage to be measured.
II. Guess the meaning of international words:
1) instrument; 2) fact; 3) abbreviation; 4) voltmeter; 5) ohm; 6) ohmmeter; 7) wattmeter; galvanometer; 9) shunt.
III. Give the Russian equivalents to the words below:
1) resistance; 2) to offer; 3) scale; 4) to prevent; 5) armature; 6) connection; 7) heating effect.
IV. Give the English equivalents to the words and word-combinations:
1) амперметр; 2) разница потенциалов; 3) определят; 4) чувствительный; 5) градуировать; 6) вставка; 7) катушка; переменный ток (второй термин).
V. Answer the questions:
1. How are electrical values measuring instruments called?
2. How must the ammeter and the voltmeter be connected?
3. What resistance must the ammeter and the voltmeter have?
4. What resulting measuring instruments do you know?
5. What types of instruments are used with both d. c. and a. c.?
6. What instruments are used only with d. c. and limited to a. c.?
VI. Make up sentences corresponding to the contents of the text:
1. A meter the potential difference in volts
2. An ammeter the resistance
3. An ohmmeter measures very small currents
4. A voltmeter electrical values
5. A galvanometer the current
1. The voltage in ohms
2. The current is measured in volts
3. The resistance in amperes
VII. Describe different types of measuring instruments and units, using the table in Task V
Список использованных источников
Основная литература
- Агабекян И.П. Английский язык для бакалавров. – Изд. 2-2, стер. – Ростов н/Д : Феникс, 2012.
- Эккерсли, К.Э. Самоучитель английского языка. – М. : Эксмо, 2011.
- Кравцова Л.И.Английский язык для средних специальных учебных заведений. Учебник. – М. : Высшая школа, 2010.
Дополнительная литература
- Бахчисарайцева М.Э., Каширина В.А., Антипова А.Ф. Пособие по английскому языку для старших курсов энергетических вузов. – М.: Высшая школа, 1983.
- Иванова К.А., Английский язык для студентов-электротехников. – Ленинград, 1983.
- Четвертакова М. М. Сборник текстов по электротехнике – Санкт-Петербург, 1999. – 48 с.
Интернет-ресурсы
- Wikipedia, Wikibooks
- English.language.ru
- www.nonstopenglish.com
- www.macmillan.ru
- www.enhome.ru
- www.study.ru
- enghelp.ru
А.С. Ефимова
13.02.11 Техническая эксплуатация и обслуживание электрического и электромеханического оборудования
Учебно-практическое пособие «Сборник профессионально-ориентированных текстов с упражнениями» для специальности 13.02.11 Техническая эксплуатация и обслуживание электрического и электромеханического оборудования (по отраслям)
2. Find in the text the sentences with the following related words and translate them:
conducting – conductor – conductivity – conductance
3. 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.
4. 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.
CAPACITORS
A capacitor is one of the main devices widely used in electrical engineering. It is used to store electric charges. Its main parts are metal plates and insulators. y S-
The insulators isolate the plates which store electric the plates. The insulators isolate the plates which store electric charges.
Capacitors are rated in farads (F). In practice units smaller than a farad are commonly used — the microfarad (mF) and the picofarad (pF).
In Fig. 2 one can see two common types of capacitors: a fixed capacitor (a) and a variable one (b). The plates of a fixed capacitor do not move. Thus its capacity does not change.
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Fig. 2 – Capacitors; a) fixed; b) variable |
The plates of a variable capacitor can be moved and its capacity changes.
The value of capacitance depends on the size of the plates and the properties of the dielectrics. It also depends on the distance between the plates: the greater the distance the less is the capacity of a capacitor.
Capacitors are produced in different sizes: from ones with extremely low capacities (1 pF) up to capacitors of extremely high capacity (1000 mF). Fixed capacitors have insulators produced of paper, ceramics and other materials. Variable capacitors have air insulators. Paper capacitors are commonly used in radio and electronics.
1. Choose the correct variant:
1. A capacitor is used a) to produce electric charges. b) to store electric charges.
2. The main parts of a capacitor are a) insulators. b) metal plates and insulators.
3. Capacitors are rated a) in farads, b) in volts, c) in microfarads.
4. The plates of a variable capacitor a) cannot be moved. b) can be moved.
5. The value of a capacitor depends on a) the size of the metal plates. b) the distance between the plates. c) the properties of the insulator.
6. Capacitors are produced a) in a few sizes. b) in many sizes.
2. Complete the sentences:
1. The plates of a fixed capacitor do not move while … . 2. The capacity of a variable capacitor varies while … . 3. The less the distance between the plates the greater the capacity … .
3. Translate the article in writing. Mind “It is … that”. Use a dictionary:
The Capacity of a Capacitor
The capacity of a capacitor is measured in farads. A capacitor has one farad capacity when a charge of one coulomb increases its potential by one volt. The farad is a very large unit. That is why it is the microfarad that is used to measure the value of capacity.
The microfarad equals one millionth of a farad. If a farad of charge is applied to the capacitor its capacity goes higher by one farad. If charges of equal values are applied to conductors of different sizes, the smaller the conductor the higher becomes its voltage.
RESISTORS. RHEOSTATS. HEATERS
A resistor is one of the most common devices used in electric circuits. Resistors are used to change the value of current and thus to change the value of voltage.
Resistors are produced in different sizes and divided into fixed and variable ones. Fixed resistors have a constant value while the value of variable resistors can be varied. When current flows through resistors their temperature increases; the higher the value of current the greater is the increase in the temperature of a resistor. Any resistor has a maximum temperature to which it may be heated. If this temperature is increased the resistor gets open and opens the circuit.
A device used in the circuit in order to regulate its current is called a rheostat. A rheostat is a wire-wound device; wires for rheostats are produced of materials having high resistivity. Commonly a comparatively short length of wire is used; it is wound on a ceramic or on some other insulator.’ «A slider moving across the windings of the rheostat changes the value of resistance between its terminals.
Another wire-wound device is a heater. Heaters, electric motors, and incandescent lamps are common loads. They are connected into the circuit in parallel since they operate at a constant voltage.
1. Translate the following words:
increase, rheostat, length, slider, winding, terminal; short, incandescent; to increase, to regulate, to call, to wind (wound, wound)
2. Translate the following word-combinations:
rheostat slider, rheostat terminals, load resistance, incandescent lamps, great increase, short lengths, long wire, circuit load; heating element, heated parts, heatable unit, reduced load, reducing value, reduceable resistance
3. Translate the following word-combinations in writing:
current-heated unit, wire-wound devices, current-carrying parts; constantly regulated voltage value, comparatively long steel wire
4. Fill in the verbs «to increase», «to regulate», «to operate», «to call»:
1. What devices are used … the value of power in the circuit? 2. Devices regulating the value of current are … rheostats. 3. When the resistor is heated its temperature … . 4. Motors should … at a constant voltage.
5. Translate the sentences. Mind «since»:
1. Porcelain is widely used as insulating material since its mechanical strength is rather high. 2. Since the temperature of the resistor had greatly increased it got open.
6. Choose the correct variant:
A resistor is used a) to reduce the value of current, b) to store electric charges.
The value of a fixed resistor is a) variable, b) fixed.
Devices used to regulate the value of current are called a) capacitors, b) rheostats.
In a wire-wound device the wire has a) low resistance, b) high resistance.
5. Different loads operate a) at a constant voltage, b) at a variable voltage.
6. The value of resistance between the terminals of a rheostat a) varies, b) does not vary.
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.
1. Translate the following words:
installation, cost, cross-section, loss, line, efficiency, per cent; certain, efficient; to ignore, to exceed; nowadays
2. Translate the words and distribute them into four columns (what? what kind? what to do? how?). Mind the suffixes:
efficiency, efficiently, to install, installation, ignorance, to ignore, ignorant, length, wide, width, widely, equal, to equal, equally, equality, to exceed, exceedingly, exceeding
3. Translate the words. Mind the prefixes:
connection-interconnection; to act-to interact; efficient-inefficient; dependent-independent; current-over-current, load-overload
4. Translate the word-combinations in writing:
inconvertible units, interdependent cross-sections, inefficient loss, interchangeable loads, overcharged cells, overheated motor, exceedingly low power losses, constantly changing power efficiency, commonly produced porcelain fuses
5. Fill in the verbs «to exceed», «to interconnect», «to ignore»:
1. Power loss in the line is extremely high; it … a certain value. 2. Various parts of this installation should be … . 3. Power loss in the line is so low that one can … it.
6. Choose the correct variant:
1. Aluminium is used due to its a) high cost. b) low cost and high efficiency.
Cross-section of different conductors a) varies. b) is the same.
Power loss can be ignored a) in short wires. b) in long wires.
A certain value of loss a) can be exceeded. b) should not be exceeded.
Electric lines nowadays are a) efficient. b) inefficient.
Installations are protected a) by switches. b) by fuses.
7. Translate the article in writing:
How to Reduce Heating Losses
When electric energy is produced at the power station, it is to be transmitted over electric wires to the consumer. Wire conductors are known to offer resistance to the current flow; the longer the wire the greater is its resistance to the current flow. Accordingly, the higher the offered resistance the greater are the heating losses in the wire.
One can reduce these undesirable losses in two ways-by reducing either the resistance or the current. To reduce the resistance, it is necessary to make use of a better conducting material and thick wires. But such wires can have a very high cost and, thus, they are considered to be inefficient.
And how can the current be reduced? One of the possible ways to do it is to utilize transformers in the transmission line.
FUSES
Fuses are widely used nowadays as protection devices. They are utilized in various circuits, electrical equipment and installations. Fuses serve to protect them against overcurrents and short-circuits.
There are different types of fuses in use nowadays. Of them, quartz-sand fuses serve for voltages up to 500 volts; fuses of this kind are produced with current ratings of 15 to 60 amp and of 100 to 350 amp.
Fuses are commonly used in low-voltage industrial installations rated up-to 1,000 V.
Fuse protection is based on a very simple principle; in case of a short-circuit or overcurrent, when the maximum value of current has been exceeded, the fusible link of a fuse is heated to its melting point. This opens the circuit and disconnects the circuit from the power source. In case of a fault, one should replace the faulty fusible element by a new one.
Fuses are used both in direct current (d.c.) and alternating current (a.c.) circuits.
1. Translate the following words:
equipment, quartz, sand, rating, case, link, fault; simple, faulty, direct, alternating; to serve, to base, to place
2. Fill in the verbs «to serve», «to reequip», «to replace»:
1. The lab should be … with modern equipment.
2. This fuse cannot … as a protective element since it is faulty. It should be … with a new fuse.
3. Translate the sentences. Mind «both … and», «in case», «up to»:
1. Both solid and gaseous insulators are in use nowadays. 2. In case an element gets open it should be replaced by a new one. 3. Capacitors of extremely high capacity (up to 1000 mF) are produced nowadays.
4. Choose the correct variant:
A fuse serves a) as a load, b) as a protection device.
Fuses are used a) for d.c. only, b) for both a.c. and d.c .
In case of a fault a) the whole fuse should be replaced, b) the faulty link should be replaced.
Fuse protection is based on, a) a simple principle, b) a complex principle
5. Translate the article in writing. Use a dictionary:
Types of Fuses in Use Nowadays
Fuses are used to protect circuits against overcurrents. In case of an overcurrent, the fuse link made of copper, zink or lead melts and opens the circuit. Zink, lead and their alloys are known to melt at a rather low temperature (200° to 240°C). These metals having a low conductivity, fuse links made from them must have a large cross-sectional area. Copper fuse links have a good conductivity, but they melt at a rather high temperature. As to silver fuse links, they are rather expensive and are known to be used at voltages over 1,000 V and low currents. Most commonly, use is made of copper fuse links silvered for protection against oxidation.
There are several types of fuses in use nowadays. Of them, a plug-type fuse has a porcelain container. Fuses of this type are used for voltages up to 380 V and currents up to 60 amp.
As to a sand fuse, it is used for voltages up to 500 V at currents from 100 to 600 amp.
6. It is interesting to know…
that the efficiency of a heat-power plant is less than half that of a water-power plant.
DIRECT CURRENT AND ALTERNATING CURRENT
We know that current is the flow of electricity through a circuit. Let us consider two main types of current: direct and alternating. A direct current flows through a conducting circuit in one direction only. It flows provided a direct voltage source is applied to the circuit.
An alternating current is a current that changes its direction of flow through a circuit. It flows provided an alternating voltage source is applied to the circuit. Alternating current flows in cycles. The number of cycles per second is termed the frequency of current. In a 60-cycle alternating current circuit the current flows in one direction 60 times per second and in the other direction 60 times per second.
Two frequencies are in use nowadays: the standard for Europe is 50 cycles per second while the standard for the USA is 60 cycles per second. A standard frequency has a great advantage since different electrical systems can be interconnected.
1. Choose the correct variant:
1. Direct current a) changes its direction of flow. b) flows in one direction.
2. Alternating current flows provided a) a direct voltage source is applied. b) an alternating voltage source is applied.
3. The frequency of the current is a) the number of cycles per minute. b) the number of cycles per second.
4. A standard frequency has a) great advantages. b) disadvantages.
5. Different systems can be interconnected a) due to various frequencies. b) due to the standard frequency.
2. Translate the extract in writing. Use a dictionary:
Current densities have greatly increased in the last two decades, due to the invention of new and better insulating materials. Besides, the methods of cooling has also changed.
Ohmic losses disappear when the windings are super cooled. Thus one can use practically any current density in the line. This technology is undergoing a test.
MEASURING DEVICES. AMMETER
According to the electrical quantity being measured, measuring devices are classed into ammeters, voltmeters, wattmeters, etc. Let us first consider the ammeter.
The ammeter serves to measure the value of current in the circuit. When the ammeter is used the circuit should be opened at one point and the terminals of the meter should be connected to it. The ammeter is connected to the circuit in series. One should take into consideration that in the process of measuring the positive terminal of the meter is connected to the positive terminal of the source.
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Fig. 3 – Connection of an ammeter in circuit |
The main part of the ammeter is its movement (зд. движущаяся часть). It has the fixed coil and a movable iron core. When the meter is used indications on the scale show the value being measured.
Ammeters are manufactured in different types. Each type serves for a certain range of measurement. In case the quantity being measured exceeds this range, faulty indications result. In such cases the measuring range of the device can be extended by a shunt or by a current transformer.
Moving-coil Ammeter. This meter is used provided the measured quantities are small. Overloading results in faulty indications. Among moving-coil ammeters are galvanometers, microammeters, and milliammeters. In them the movement is connected in parallel with the shunt. Meters of this type are widely used nowadays for engineering measurements. Their advantages are their low cost and their simple construction.
1. Translate the following words:
quantity, consideration, measurement, coil, core, indication, scale, range, shunt; to measure, to take into consideration, to extend, to result (in, from)
2. Fill in the verbs «to exceed», «to result in», «to result from», «to indicate», «to extend»:
1. The range of the meter is small; let us use a shunt to … it. 2. Overloading … faulty indications. 3. A fault in the device may … its constant use. 4. Overcurrent … faulty measurements. 5. Measured quantities should not … a certain range; in case they … this range the meter gives faulty indications.
3. Translate the following sentences:
Let us measure the current in the circuit. Take into consideration the range of the meter. Read the indications off the scale.
4. Choose the correct variant:
1. The ammeter is used to measure a) the value of current. b) the value of power.
2. The main part of the meter is a) its scale. b) its coil. c) its movement.
3. Faulty indications result from a) short-circuits. b) overcurrents.
4. Overcurrents result in a) power loss. b) faulty indications.
5. A shunt is used in order to a) extend the range. b) indicate the range.
VOLTMETER
Voltmeter is used to measure the value of voltage in the circuit. When the voltmeter is being used its positive and negative terminals are connected to the circuit in parallel.
The voltmeter movement is similar in its construction to the ammeter movement: it includes a coil and a high resistor. The scale is calibrated in volts.
In a.c. circuits, in addition to series resistors, the range of measurement is extended by an instrument voltage transformer.
In d.c. circuits, moving-coil meters are commonly used. Their accuracy does not depend either on the value of the external of a voltmeter in magnetic fields or on the temperature.
Fig. 4 – Connection of a voltmeter in circuit
It depends only on the load. Overloading of the meter results in faulty indications. In order to extend the range of measurements either moving-coil or moving-iron devices are applied.
Moving-iron devices are used in a.c. circuits at power (commercial) frequency. They are produced in accuracy classes 0.1-2.5. Their advantages are a low cost, simplicity of construction and reliability of operation.
1. Translate the following words:
accuracy, field; similar, external, reliable; to calibrate, to rely on (upon)
2. Translate the words and distribute them into three columns (what? what kind of? what to do?). Mind the suffixes:
to rely on, reliability, reliable, unreliable, simple, simplicity, accurate, accuracy, similarity, similar, external, inaccurate, dissimilarity, advantageous, disadvantage
3. Translate the word-combinations in writing:
reliable simplicity, unreliable inaccuracy, internal similarity, disadvantageous position, externally interconnected installations, similarly constructed cells, low accuracy class meters, magnetic field range, instrument voltage transformer
4. Translate the sentences. Mind «either … or»:
1. Measuring devices should be connected to the circuits either in series or in parallel. 2. The measuring range of the meter can be extended either by a shunt or by a current transformer.
5. Choose the correct variant:
1. The voltmeter movement a) is similar to the ammeter movement. b) is different from the ammeter movement.
The accuracy of the meter depends on a) the external magnetic field. b) the load.
Low cost and reliability are a) advantages. b) disadvantages.
6. Complete the sentences:
1. The ammeter is used to measure the value of current while … . 2. The ohmmeter is connected to the circuit in parallel while … . 3. High cost and unreliability are disadvantages while … .
7. Answer the questions:
1. What part of the voltmeter is similar to that of the ammeter? 2. What does the accuracy of a moving-coil meter depend on? 3. What does overloading in the circuit result in? 4. What are the advantages of moving-coil devices?
8. Translate the text in writing:
Electrodynamic Voltmeter
This type of meter includes an electrodynamic movement. Its coils are connected to a series resistor, which serves to extend the range of the instrument and to minimize the effect of temperature variations.
The voltmeter is used both in a.c. and d.c. circuits ; its accuracy class is from 0.1 to 0.5.
OHMMETER
Ohmmeters are widely used nowadays for measuring the value of resistance. The main part of the meter, as in any other direct-indicating device, is its movement. In the ohmmeter’s movement either an external or an internal permanent magnet is used.
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Fig. 5 – Parallel-circuit ohmmeter whose indications depend on supply voltage |
The operation of the device either depends on the supply voltage or does not depend on it. Accordingly, the meters are classed into two groups. 1. Meters having a moving-coil movement with two coils on a common shaft. The currents in these coils flow in the opposite directions and, accordingly, two torques are produced. These torques also act in the opposite directions. In the meters of this type a generator serves as a supply source. 2. Devices having a moving-coil movement with a series resistor. In them a battery serves as a supply source.
1. Fill in the verbs «to supply», «to serve as», «to consider», «to act»:
1. Measuring devices are … in units 13-16. 2. Voltage sources … circuits with electric power. 3. The shaft … a base for the coils. 4. The torques produced … in the opposite directions.
2. Translate the sentences. Mind «accordingly»:
1. Meters are used to measure the values of current, voltage, resistance, etc. Accordingly, they are classed into ammeters, voltmeters, ohmmeters, etc. 2. The ohmmeter includes a moving-coil movement with a series resistor; accordingly, in it a battery is used as a supply source.
3. Choose the correct variant:
The ohmmeter serves to measure a) power. b) resistance.
Its movement a) does not include a permanent magnet. b) includes a permanent magnet.
A moving-coil movement has a) coils on two different shafts. b) coils on one common shaft.
In the coils a) two torques are produced. a) one torque is produced.
The currents in the coils flow a) in one direction. b) in two opposite directions.
4. Answer the questions:
1. What does the ohmmeter serve for? 2. What type of magnet does its movement include? 3. How many shafts has the meter? 4. How many torques are produced in the coils? 5. In what directions does the current in the coils flow?
5. Translate the text in writing. Use a dictionary:
Three-Unit Wattmeter
The active power in a four-wire three-phase network is measured by three wattmeters.
These devices are connected as shown in Fig. 6, each wattmeter measuring the power in one phase.
It is advantageous to use a three-unit wattmeter since it includes three fixed coils and three movable coils driving a common shaft. The power in a three-phase network can, in this case, be read directly off the device scale.
The power of a symmetrical three-phase -network is found by measuring the power in one phase and multiplying it by three.
6. Render the text in Russian:
Lamps for Music-Making
Lamps for music-making? Certainly. There is a group of gas-discharge lamps, called neon glow lamps, whose lights are used as components in electrical circuits. In electronic organs, for example, glow lamps are used as switches that produce light when energized by a key. The light is then modulated to the proper frequency. This «note» is then converted into an electrical signal which is amplified; so in effect the lamp is producing light that we hear rather than see.
MEASUREMENT OF INSULATION RESISTANCE
According to the code for operation of electrical installations, the minimum insulation resistance is 0.5 megohm. The insulation resistance of lighting and power circuits is measured with a megohmeter. When it is done all the fuses should be removed and the circuit breakers or relays deenergized. The resistance is measured between fuses, or any other protective devices, between any wire and earth and also between any two wires. In the process of measurement one terminal of the megohmeter is connected to the wire and the other terminal to the earthing system. The indications are read off the scale.
The insulation resistance of electrical installations should be checked regularly. If a fault is detected, the faulty part should be eliminated and replaced by a new element.
A fault in the protective part is dangerous for the attending personnel since it may result in an electric shock. For protection against shocks a safety earthing system is used.
1. Choose the correct variant:
The insulation resistance should be checked a) regularly. b) sometimes.
The circuit breakers should be a) energized. b) de-energized.
One terminal should be connected a) to the fuse. b) to the wire.
The other terminal should be connected a) to the protective device. b) to the earthing system.
The faulty part should be a) energized. b) removed.
2. Answer the questions. Use them in a talk with your groupmate:
1. What device is used to measure the insulation resistance? 2. How often should the insulation resistance , be checked? 3. Why should the circuit breaker be deenergized? 4. To what parts should the terminals be connected? 5. What should be done with faulty parts? 6. Why is faulty resistance dangerous for attending personnel?
3. It is interesting to know that…
a man can get an electric shock when he comes into contact with the electric fish. One of this kind is found in the tropical waters of South America: it is the electric eel. Small electric eels, one inch long, give a small shock. When the fish is 6 inches long its internal battery gives as much as 200 volts. A very big fish can generate 600 volts! When it is short-circuited, a current of one ampere can be obtained. A two-meter long eel can light a dozen 50 watt lamps. The eel’s head is positively charged and the opposite end is negatively charged.
4. Read the following statements; say whether they are true or false and compare your answers with those given below:
An ammeter is used properly when its terminals are connected to the battery supply. Is it true or false?
One should use an ammeter’s lowest current range during reading indications in order to keep the meter’s internal resistance to a minimum. Is it true or false?
Cleaning a meter face with dry cloth may reduce reading accuracy. Is it true or false?
5. Translate the words and word-combinations:
unreliability, interchange, externally, decentralize; oil-supplied installation, indirectly proportional value, external and internal magnetic fields
6. Use English words instead of the Russian ones:
1. One should (проверять) electric equipment regularly.
2. Electric shock is (опасен) for attending personnel.
3. Faulty elements should be (устранены).
CIRCUIT-OPENING DEVICES. SWITCHES
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Fig. 9 – Quick-break knife-blade switch: a) “on” position; b) “off” position |
Any circuit can be divided into an internal and an external part. The internal part consists of the energy source while the external includes the load and the wires.
In addition to these three components, electric circuit utilizes various circuit-opening devices. These devices are classed into non-automatic and automatic. To non-automatic or manually operated devices, belong, switches and controllers. There are different types of switches: knife-switches, packet-switches and others.
The knife-switches are used to start electrical machines. D.c. and a.c . electric circuits are opened and closed by means of knife-switches under normal conditions; they are disconnected by knife-switches under abnormal conditions at no load.
As to packet-switches, they are used to switch on and off electric motors and to close or open electric circuits rated up to 380 V.
Controllers are used in special starting conditions. A controller brings resistors in and out of circuits in order to start, stop or reverse motors. It closes and opens different circuits at different times.
After a switch or a controller is installed it should be given a test. It should be also checked for faultless operation. The device is checked in the on-position and in the off-position. In case the device being checked produces noise or fails to operate, it should be rechecked. The faulty part should be detected and eliminated.
1. Choose the correct variant:
A switch serves a) to start motors, b) to open and close circuits.
The resistance of the switch in the on-position a) is extremely high, b) is rather low.
The external circuit consists of a) the energy source and the wires, b) the load and the wires.
Knife-switches belong to a) manual devices, b) automatic devices.
Motors are started, stopped and reversed a) by means of controllers, b) by means of switches.
Electrical devices should be checked a) in the on-position, b) in the off-position.
2. Complete the sentences:
1. The internal circuit includes the energy source: as to … . 2. Switches belong to non-automatic devices; as to … . 3. The knife-switches can operate under abnormal conditions; as to … .
3. Answer the questions:
1. What does а switch serve for? 2. What is the resistance of the switch in the on- and in the off-position? 3. What elements does the external (internal) circuit consist of? 4. What devices belong to manually operated ones? 5. What do controllers serve for? 6. In what position should the devices be checked for faultless operation?
4. Render the extract in English. Demonstrate the operation of а switch while rendering:
Switches are commonly used to open and close circuits. Closed is the on-position; open is the off-position. The switch is in series with the voltage source and its load. In the on-position the closed switch has а very low resistance, which results in maximum current in the load with zero voltage loss across the switch. When the switch is off it has very high resistance and no current flows in the circuit.
5. Translate the text in writing. Use а dictionary:
Disconnecting switches
Application. Indoor disconnecting switches are devices that are intended to make and break electric circuits rated at 6 to 10 kV, a.c. with no load currents. The single-pole disconnecting switches are controlled manually, by means of an insulated rod. The triple-pole disconnecting switches are controlled by means of manual lever-type operating mechanisms.
Mounting Instructions. 1. Clean the switch from dust and dirt. 2. Inspect it on the outside. 3. When insulating the switch, see that the bolts and switch terminals are reliably protected.
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Fig. 10 – Schematic positioning of the different contactor components: 1 — fixed bar; 2- magnetic circuit; 3- auxiliary contacts; 4 — poles |
6. Translate the article. Describe Fig. 10:
Contactors Туре 370
These contactors consist of the following main parts:
— one fixed bar;
— one magnetic circuit which may be either a.c. оr d.c.;
— one or more auxiliarly contacts (the maximum number of auxiliary contacts is 4);
— one or more poles for use with a.c. or d.c. loads.
These components are to be installed.
Their functions are as follows: fixed bar has the function of supporting all the stationary parts of the contactor. At both ends it is provided with holes for mounting the contactor. Moving shaft is made of steel. It is insulated for the installation of both main pole and auxiliary moving contacts.
RELAYS
Relays are electromagnetic devices widely used in various branches of industry. Relays are designed for rather low currents and for operation in control circuits at low voltages.
Ву means of а relay electric current flowing in one circuit can open or close а second circuit and thus control the switching on and off of а circuit.
The main components of а relay are an electromagnet, an armature and а spring. As to contacts, they belong to its auxiliary elements. When а current starts flowing in the electromagnetic winding, the armature moves and the spring closes the contacts. When there is no current in the primary circuit, the spring pulls the armature and the contacts open.
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Fig. 11 – Electromagnetic relay in operation |
Fig. 11 shows how а relay is used to control the work of an electric motor. The relay is placed close to the motor which is connected to its secondary circuit. The armature closes the contacts of the secondary circuit, and the motor starts operating. It stops when the relay opens.
The primary circuit is operated either manually or automatically. Every evening and morning street lights are switched on and off from the main panel by means of relays.
As to thermal relays, they use а bimetallic thermal elements. This element consists of two metals differing in thermal coefficients. When the element is heated it actuates the device. It can be heated either directly by the current flowing in it or indirectly by а heater.
1. Translate the sentences. Mind «no»:
1. No heating element can actuate this device. 2. No auxiliary springs were utilized to pull the armature. 3. The switches are faultless; they produce no noise in operation. 4. The operators used no additional springs since no additional components were needed to actuate the relay.
2. Choose the correct variant:
1. Relays are designed for а) low currents. b) high currents.
2. А relay consists of а) а spring and an armature. b) an electromagnet, an armature and а spring.
3. The relay is placed а) close to the motor. b) far from the motor.
4. The motor is connected to а) the primary circuit. b) the secondary circuit.
5. Street lights are switched on and off а) by means of relays. b) by means of controllers.
6. The bimetallic element is heated а) directly. b) indirectly. с) both directly and indirectly.
3. Answer the questions:
1. For what value of current are relays designed? 2. What main parts does а relay consist of? 3. То which circuit is the motor connected? 4. By what means are street lights switched on and off? 5. How is the bimetallic thermal element heated?
4. Translate the text in writing. Use а dictionary:
Magnetic Thermal Relay
Application. This relay is designed for the overload protection of motors connected to а single-phase or to а three-phase a.c. supply. The thermal unit matches the motor temperature and protects it against overloads.
Construction. The relay consists of two main parts: the magnetic unit and the contact box. The magnetic unit includes two coils on а horizontal shaft. А primary coil – for the current to be controlled and а secondary coil connected to а bimetallic bar. The parts of the relay are installed close to each other on а base of insulating material.
Operation. The current to be controlled flows through the primary coil and produces both а magnetic field and а current in the secondary coil. This current flows through the bimetallic bar and heats it. When the current increases above the maximum value, the bar warps. The contaet on the shaft is opened.
TRANSFORMER
А transformer is used to transfer energy; due to the transformer electric energy may be transferred at а high voltage and reduced at the point where it must be used to any value. Besides, а transformer is used to change the voltage and current value in а circuit.
А two-winding device consists of а closed core and two windings (coils). The primary winding is connected to the voltage source; it receives energy. The secondary winding is connected to the load resistance; it supplies energy to the load.
The value of voltage in the secondary winding depends on the number of turns in it. In case the secondary winding has more turns than the primary, the output voltage is greater than the input voltage. А device of this type steps up the voltage and is termed а step up transformer (see Fig. 12). In case the secondary winding has fewer turns than the primary, the output voltage is lower than the input. This device decreases or steps down the voltage. It is termed а step down transformer.
Let us compare Т1 and Т2. Т2 has an iron core: it is used for low frequency currents. T1 has an air core and is used for high frequencies.
The core and the windings are placed in а metal tank. The tank contains the insulating oil, which protects the device from overheating and cools its parts. The higher is the capacity of the device the greater is the cooling required.
Each transformer has а nameplate attached to the tank. It bears the transformer’s ratings, its type, its capacity, number of phases, group of winding, frequency, duty ratings, method of cooling, indoor or outdoor, mass, the name of the plant and some other data.
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Fig. 12 – Transformers: a) step-down T b) step-up T |
Fig. 13 – Transformers: a) air-core T b) iron-core T |
When the new transformer is installed its tank is earthed. After that the device is given а test to check its operation. During the test one should listen to its noise by means of а bakelite tube, 1 meter long. In the case of the abnormal noise or in the case of oil decrease in the tank, the device should be switched off and examined.
Common faults in а transformer are an open in the winding, а short between the primary and the secondary, and а short between turns. Shorted turns are due to periodic overloads or dynamic stress. An open may result from overheating. Stresses result from short circuit currents.
In case а transformer has а fault, it stops operating or its operation is poor. А faulty element should be eliminated and replaced by а new one.
The transformer forms one of the main parts of а substation.
1. Translate the following words:
winding, turn, input, output, tank, nameplate; poor; to transfer, to receive, to step up, to step down, to contain, to cool, to require, to attach
2. Translate the word-combinations in writing:
а) input voltage, voltage output, step up transformer, step down transformer, regular operation, poor results
b) modern network protection relay, high-voltage current transformer, faultlessly operating step up transformer, poorly operating step down transformer, external hard porcelain insulator
3. Fill in the verbs «to attach», «to contain», «to receive», «to supply», «to require»:
1. Any operating transformer … cooling; thus its tank … cooling liquid. 2. The new apparatus is to be … to the panel; this attachment is not simple. It … experience. 3. The Т windings … and … electric energy. 4. Any device … testing.
4. Choose the correct variant:
1. А transformer is used а) to reduce power. b) to receive power. с) to transfer power.
2. The primary winding а) receives energy. b) supplies energy.
3. А step down transformer а) increases the voltage. b) decreases the voltage.
4. А transformer with an iron core is used а) for low frequency currents. b) for high frequency currents.
5. The nameplate is attached а) to the frame. b) to the tank.
6. The tank contains а) air. b) oil.
7. Faults in а transformer result from а) overheating. b) stresses. с) short-circuits.
5. Complete the sentences:
1. The primary winding receives energy while … . 2. А step down transformer decreases the voltage while … . 3. А transformer with an air core is used for high frequencies while … . 4. In a step up transformer the number of turns in the secondary winding is greater that the number of turns in the primary while … . 5. The greater is the quantity of heat the greater is the cooling required while … .
6. Answer the questions:
1. What is а transformer used for? 2. What parts does it consist of? 3. What is the function of the primary (secondary) winding? 4. What is the difference between а step up and а step down Т? 5. What frequencies is an air (iron) core Т used for? 6. Where are the core and the windings placed? 7. What liquid does the tank contain? 8. Why does а Т require cooling? 9. What are the common faults in а Т? 10. What do they result from? 11. То what part is the nameplate attached? 12. What data does it bear?
7. Translate the text in writing. Use а dictionary:
High-Voltage Transformer
А great number of different types of transformers are in use nowadays. А high-voltage transformer is one of the newly constructed ones.
This transformer is intended for outdoor installation. Its highest system voltage is 75.5 to 525 kV; maximum number of cores is 6 and frequency – 50 and 60 Hz.
The transformer is applied in high voltage installations and for energization of network protection relays. The device has unlimited electrodynamic short-circuit strength of the primary conductor. Protection cores are suitable for overcurrent requirements as well as for reliable transformation of short-circuit currents. For external insulation hard porcelain is used and for the main insulation paper / oil insulation is used.
8. Translate the words and the word-combinations:
disappearance, overproduction, uselessness, outdoor, indoor, poorly operating relay, manually-operated switch, unearthed live tank
BATTERIES
An Italian scientist Alessandro Volta made a lot of experiments with electricity. Batteries as sources of electrical energy are the result of his experiments.
Today battery cells are produced in two common forms: dry cells, used in flashlights, portable radios, clocks, cameras and (well) wet cells, used in automobiles, airplanes, boats.
The voltaic cell is composed of three parts: a pair of dissimilar metal plates called electrodes, a dilute acid solution called electrolyte, and a nonconducting container called the cell. In a glass container filled with sulphuric acid there are two plates: one copper and are connected by a copper wire, electricity will flow through it from the copper plate to the zinc plate.
For the voltaic cell the copper plate is the positive electrode and the zinc plate the negative electrode a copper wire will convey electricity and is called an electrical conductor. Copper, aluminium and silver are good conductors. They must be surrounded by protective material which does not conduct electricity. Such materials are called electrical insulators (glass, wood, rubber, some plastics, insulation tape)
Remember that faulty insulation is dangerous and leads to unwanted electrical flow and probably to local overheating.
Vocabulary:
Страницы работы
Фрагмент текста работы
Recollect the sentences from the text in which these expressions were used or make up sentences of your own.
Make acquaintance … smb, … … the
ordinary, … … office, admiration …, akin …, prevent smb …, be indifferent …, to
deal …, say smth … the subject, passion …, distinguish smb/smth …, eke …, …
regard …, have an eye …, ferret …, throw discredit … smb.
V. Insert the necessary key words or expressions to complete the sentences below:
1. The headteacher gave a … speech about 'the values of learning'.
2. Let us come before him with thanksgiving and … him with music and song.
3. The almond cake is particularly ….
4. See if you can solve this ….
5. The Lorrimores had arrived, each wearing yesterday's expression: pleasant, aloof, …, sulky.
6. To the … all these plants look pretty similar.
7. She had a great … for absorbing information.
8. Within families filial … was the keystone of morality and it led logically to an absolute obedience to the household head.
9. The public is willing to forgive him for his ….
10. So a government scientist, whom out of modesty I … to name, had to expose the fraud.
11. Abusing a child is a … act.
12. The movie's special effects are absolutely ….
13. The problem which immediately strikes one is that much of the material is …, fragmented, and lacking unity.
14. People are still … because they are miserable.
VI. Give the English equivalents of the following expressions and reproduce the situations in which they were used.
Предмет насмешек, необычный,
удовлетворять эстетическое чувство, пробуждать интерес, невежество, талантливый
писатель, исчерпывающе анализировать, привлечь внимание, подлинный гений,
удовлетворять любопытство, дар, мало-помалу, пламенный поклонник, опозорить.
VII. Translate these sentences into English by using the words and word combinations from the text.
1. А сейчас вряд ли кто станет отрицать его величие.
2. Величие Чарлза Стрикленда было подлинным величием.
3. Прошли времена, когда оно было предметом насмешки.
4. Нелепейшее заблуждение - почитать искусство за ремесло, до конца понятное только ремесленнику.
5. Искусство - это манифестация чувств, а чувство говорит общепринятым языком.
6. В человеке заложена способность к мифотворчеству.
7. Меня, например, очень огорчила бы мысль, что Антония и Клеопатру не связывало ничего, кроме экономических интересов.
8. Ни одному мистику не удавалось лучше прозреть скрытый смысл в обыденном.
9. Это было увлекательное занятие: следить, с каким рвением ученый автор выискивал малейшие подробности, могущие опозорить его героя.
10. Трудолюбие его достойно изумления.
VIII. Answer the following questions.
1.
Who do you think
are going to be the main characters of the novel? What makes you think so?
2.
Is the story
produced by the narrator the first one dedicated to Charles Strickland? What
for does he mention other authors? What is the author’s attitude to those
books?
3.
Do the books show
their readers a real Strickland? Support your answer with the text.
4.
What do we get to
know about Charles Strickland? Underline sentences and phrases that can be used
for Strickland’s character sketch. Is there anything that doesn’t let you
respect that person? Comment on the phrase “Nothing was too small to escape
him”.
5.
Speak on the
author’s idea of art and artists. Do you support it?
IX. Comment on the following statements:
1.
Greatness which
is achieved by the fortunate politician or the successful soldier is a quality
which belongs to the place he occupies rather than to the man; and a change of circumstances
reduces it to very discreet proportions.
2.
His faults are
accepted as the necessary complement to his merits.
3.
To my mind the
most interesting thing in art is the personality of the artist; and if that is
singular, I am willing to excuse a thousand faults.
4.
The layman can
understand nothing of painting, and that he can best show his appreciation of
their works by silence and a cheque-book.
5.
Art is a
manifestation of emotion, and emotion speaks a language that all may
understand.
6.
The faculty for
myth is innate in the human race.
Chapter 2
I.
Work
with a dictionary to learn the meaning of the following words.
Superfluous
Precept
Tedium
Censure
Hollow
Chasten
Sate
Clamor
Scorn
Pendulum
Stir
Realm
Desultorily
Fervid
Ethereal
Felicity
Stomach (v)
II. Reproduce the situations in which the active vocabulary is employed.
III.
Find pairs of synonyms among the following words (12
pairs
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