Электроэнергетика и электротехника

МЕТОДИЧЕСКИЕ УКАЗАНИЯ ПО ВЫПОЛНЕНИЮ ПРАКТИЧЕСКИХ РАБОТ ПО ДИСЦИПЛИНЕ

«АНГЛИЙСКИЙ ЯЗЫК»

 

Направления подготовки:

Электроэнергетика и электротехника

Бакалавриат

Изучается в 4 семестре

 

Ставрополь

2017

 

 

Методические указания по выполнению практических работ по дисциплине «Английский язык» для студентов специальности 130302  «Электроэнергетика и электротехника» / сост.: Новицкая А. В.,

Цвецих О. А.. – Ставрополь: Изд-во СКФУ, 2017. – 120 с.

 

 

Методические указания составлено в соответствии с Федеральным государственным образовательным стандартом высшего профессионального образования, рабочим учебным планом и программой. Содержит курс практических занятий, включающих тексты для чтения и перевода, вопросы и задания, словарь (предтекстовый), лексико-грамматические упражнения (послетекстовые), литературу.

Предназначено для студентов специальности 13.03.02 «Электроэнергетика и электротехника

 

 

Составители:

канд. пед. наук, доцент А. В. Новицкая,

ст. преподаватель О. А. Цвецих

 

Рецензент

канд. филол. наук, доцент Л. М. Митрофаненко

 

 

                                                                                   

	© А. В. Новицкая, О. А. Цвецих, 2017
	© ФГАОУ ВО «Северо-Кавказский               федеральный университет», 2017

 

 

Предисловие

Стремительное развитие науки и техники, а также расширение экономических и культурных связей обусловили необходимость эффективного обмена информацией между всеми странами мирового сообщества. Английский язык традиционно считался языком торговли, политики, спорта и науки, но с появлением компьютеров и всемирной сети Интернет он приобрел статус поистине международного.

Согласно статистическим данным, около 80 % Интернет-сайтов и 75 % научной литературы написано на английском языке. Стремительное развитие добычи нефти и газа, а также поиск и разработка новых запасов этого топлива создают спрос на специалистов, способных эффективно работать в любой стране. Поэтому современный специалист по бурению нефтегазовых скважин должен не только быть компетентным в своей области знаний, но и уметь получать знания и навыки путем ознакомления с новыми достижениями и разработками в этой области.

Быстрое развитие новых технологий и оборудования порождает все новые термины. Кроме того, семантика некоторых терминов со временем изменяется. Трудности перевода заключаются в выборе правильного значения многозначного иностранного термина. В данных указаниях активируются более 1000 слов и словосочетаний, которые относятся к наиболее распространенной специальной лексике.

Основной целью пособия является развитие навыков чтения и пере-вода специализированных текстов по предлагаемым темам. Оно призвано научить пользоваться общими и специальными словарями и справочниками при чтении и переводе научно-технической литературы.

Пособие способствует формированию коммуникативной компетенции, уровень которой на отдельных этапах языковой подготовки позволяет практически использовать иностранный язык в профессиональной деятельности.

Поставленная цель определяет задачи изучения иностранного языка в высшей школе, а именно:

· приобретение студентами языковой и коммуникативной компетенции, необходимой для изучения зарубежного опыта в определенной области науки и техники, а также для осуществления деловых контактов;

· формирование навыков поиска и обработки информации на иностранном языке;

· формирование навыков аргументировано и ясно строить устную и письменную речь на иностранном языке;

 

В результате усвоения тем и разделов дисциплины, работы на практических занятиях у обучающихся должна сформироваться способность к коммуникации в устной и письменной формах на русском и иностранных языках для решения задач межличностного и межкультурного взаимодей-ствия (ОК-5); способность к самоорганизации и самообразованию (ОК-7).

В результате освоения дисциплины обучающийся должен знать:

· профессиональную терминологию на изучаемом языке;

· грамматические и лексические структуры устной и письменной речи в определенном объеме;

· словообразовательную структуру общенаучного и терминологического слоя текста по специализации;

уметь:

· переводить общие и профессиональные тексты с иностранного языка,

· правильно и аргументировано формулировать мысль в устной и письменной формах на родном и иностранном языке;

владеть:

· навыками устной и письменной речи на иностранном языке.

 

При отборе текстового материала учитывалась информационная ценность текстов и их соответствие интересам студентов.

Дисциплина изучается в 4 семестре. |

 

Lesson 1. Electric Circuit

 

1. Read and learn the words:

 

Circuit - цепь, контур

Conductor - проводник

Function -  назначение

Difference - разница

Open - обрыв

Short - короткое замыкание

Trouble - повреждение

to reduce - сокращать

to supply - снабжать

to connect - связывать

to compare (with) - сравнивать (с)

to pass through - проходить через

to result in - приводить к, иметь результатом

to result from - следовать, проистекать из

2. Translate into Russian:

 

1. An open and a short are troubles in a circuit.

2. A trouble in a circuit results in no current in it.

3. What does an open in a circuit result in?

4. What does a short in a circuit result in?

5. What does a trouble in a circuit result from?

 

3.
Read and translate the text.

Electric Circuit

This is a circuit. Its elements are a voltage source, a resistor and a conductor. The circuit consists of a voltage source, a resistor and a conductor. A voltage source supplies current. A resistor reduces current. A conductor connects the elements of the circuit. Compare circuit a with circuit b. What is the difference between them? Current passes through circuit a while no current passes through circuit b. Circuit b has an open. No current through circuit b results from an open. An open and a short are troubles in a circuit. A trouble in a circuit may result in no current in it.

 

4. Complete these sentences, using the correct variant:

1. Circuit a consists of

a) resistors and conductors.

b) a voltage source and resistors.

c) a voltage source, a resistor and a conductor.

 

2. A voltage source

a) conducts current.

b) reduces current.

c) supplies current.

 

3. A conductor

a) connects the elements.

b) supplies voltage.

c) conducts current.

 

4. A resistor

a) connects the elements.

b) supplies current.

c) reduces current.

 

5. No current results from

a) an open.

b) a short.

 

Lesson 4. Meters

 

1. Read and learn the words:

meter - измерительный прибор

battery - батарея

scale - шкала

readings - показания на шкале (прибора)

terminal - клемма

positive - положительный

negative - отрицательный

to measure - измерять

to take into consideration - принимать во внимание

in this way - таким путем, таким образом

 

Meters

Among the most common meters used there are the ohmmeter, the ammeter and the voltmeter. The ohmmeter is used to measure the value of resistance. It consists of a milliammeter calibrated to read in ohms, a battery and resistors. The meter is connected in parallel and the circuit is not opened when its resistance is measured.

The readings on the scale show the measured value. The ammeter is used to measure the value of current. When the ammeter is used the circuit should be opened at one pointand the terminals of the meter should be connected to it. One

should take into consideration that the positive terminal of the meter is connected to the positive terminal of the source; the negative terminal - to the negative  terminal of the source. The ammeter should be connected in series. The readings on the scale show the measured value.

 

3. Complete the sentences using the correct variant:

1. The ammeter is

a) a common meter.

b) an uncommon meter.

 

2. In order to measure the value of current

a) the ohmmeter is used,

b) the voltmeter is used.

c) the ammeter is used.

 

3. A meter has

a) positive terminals only.

b) negative terminals only.

c) positive and negative terminals.

 

4. When the ammeter is used

a) the circuit should be opened.

b) the circuit should not be opened.

 

5. The ammeter should be connected

 a) in series,

b) in parallel.

 

6. One should take into consideration that

 a) the positive terminal should be connected to the negative terminal.

b) the positive terminal should be connected to the positive terminal of the source.

 

Lesson 5. Resistors

1. Read and learn the words:

capacity - емкость

power - мощность

heat - теплота, нагрев

rate - скорость, степень

to produce - производить

to change - менять(ся)

to vary - варьировать(ся)

low - низкий

high - высокий

fixed – постоянный

any - (зд.) любой

variable - переменный

the (more)... the (more) чем (больше)... тем (больше)

 

2. Translate into Russian using чем... тем:

1. The more one studies nature, the better one knows its laws.

2. The longer one learns, the more one knows.

3. The higher the atmosphere, the less is its pressure.

4. The heavier the object, the more work one has to do in order to lift it.

5. The greater the number of free electrons in any metal, the higher is its

conductivity.

 

3. Translate into Russian. Mind no.

1. There is no energy in this machine.

2. No charges move through an open circuit.

3. No material is a perfect conductor of electricity.

4. No electric machinery is used without protection.

5. No special material is needed in this case.

 

Resistors

A resistor is one of the most common elements of any circuit. Resistors are used: 1. to reduce the value of current in the circuit; 2. to produce IR voltage drop and in this way to change the value of the voltage. When current is passing through a  resistor its temperature rises high. The higher the value of current the higher is the temperature o f a resistor. Each resistor has a maximum temperature to which it may be heated without a trouble. If the temperature rises higher the resistor gets

open and opens the circuit. Resistors are rated in watts. The watt is the rate at which electric energy is supplied when a current of one ampere is passing at a potential difference of one volt. A resistor is rated as a I-W resistor if its resistance

equals 1,000,000 ohms and its current-carrying capacity equals I/1,000,000 amp, since P = E x I = IR x I = I²R where P - power is given in watts, R - resistance is given in ohms and I - current is given in amperes. If a resistor has a resistance of only 2 ohms but its current-carrying capacity equals 2,000 amp, it is rated as a 8,000,000-W resistor. Some resistors have a constant value - these are fixed resistors, the value of other resistors may be varied - these are variable resistors.

 

5. Complete the sentences using the correct variant:

1. A resistor is used

a) to measure the resistance.

b) to reduce the current.

c) to change the resistance.

d) to produce IR voltage drop.

 

2. When current passes through a resistor

 a) its temperature drops.

b) its temperature rises.

 

3. Resistors are rated

a) in ohms.

b) in volts.

c) in watts.

 

4. Power is given

a) in amperes.

b) in watts.

 

5. Fixed resistors have

a) a constant value.

b) a variable value.

 

6. The value of a variable resistor

a) is fixed.

b) is varied.

 

7. A two-ohm resistor rated as a 8,000,000-W resistor

a) has a current-carrying capacity equal to 2,000 amp.

b) has a current-carrying capacity equal to 200 amp.

 

Lesson 6. Electric Cells

1. Read and learn the words:

Cell - элемент

output - емкость, мощность

bulb - электрическая лампа

to light - зажигать, освещать

to increase - увеличиваться), возрастать

to substitute - заменять

...and so on - и так далее

 

Electric Cells

An electric cell is used to produce and supply electric energy. It consists of an electrolyte and two electrodes. Electrodes are used as terminals, they connect the cell to the circuit - current passes through the terminals and the bulb lights.

Cells can be connected in series, in parallel and in series-parallel. In order to increase the current capacity cells should be connected in parallel. In order to increase the voltage output cells should be connected in series. In case a battery has a large current capacity and a large voltage output, its cells are connected in series-parallel.

When cells are connected in series the positive terminal of one cell is connected to the negative terminal of the second cell, the positive terminal of the second cell - to the negative terminal of the third... and so on.

When cells are connected in parallel their negative terminals are connected together and their positive terminals are also connected. In case a cell has a trouble it stops operating or operates badly. This cell should be substituted by another one.

 

 

3. Complete the sentences using the correct variant:

 

1. A cell is used

a) to increase the voltage output.

b) to reduce the current capacity.

c) to supply electric energy.

 

2. The terminals of a cell are used

a) to conduct current.

b) to increase voltage.

c) to connect the battery to a circuit.

 

3. When cells are connected in series

a) all the positive terminals are connected together.

b) all the negative terminals are connected together.

c) the positive terminal of one cell is connected to the negative terminal of the second.

 

4. Cells are connected in series in order

a) to increase the current capacity.

b) to increase the voltage output.

 

5. In order to increase the current capacity

 a) cells are connected in series,

b) cells are connected in parallel.

 

4. Answer the following questions:

1. What is a cell used for?

2. What does a cell consist of?

3. What is the function of the terminals?

4. In what way are cells connected in order to increase the voltage output?

5. In what way are cells connected in order to increase the current capacity?

6. In what way are the terminals of series cells connected?

7. In what case does a cell stop operating?

8. What should be done in case it stops operating?

 

Lesson 7. Capacitors

1. Read and learn the words:

capacitor - конденсатор

insulator - изолятор

frequency -  частота

distance -  расстояние

advantage - преимущество

disadvantage -  недостаток

plate - анод (лампы)

part - часть

to apply - прилагать, применять

to move - двигать(ся)

to prevent -  предотвращать

reason - причина

for this reason - по этой причине

besides - кроме того

provided that - при условии что

Capacitors

A capacitor is one of the main elements of a circuit. It is used to store  electric energy. A capacitor stores electric energy provided that a voltage source is applied to it.

The main parts o f a capacitor are metal plates and insulators. The function of insulators is to isolate the metal plates and in this way to prevent a short.

In the diagram one can see two common types of capacitors in use nowadays: a fixed capacitor and a variable one. The plates of a fixed capacitor cannot be moved; for this reason its capacity does not change. The plates of a variable capacitor move; its capacity changes. The greater the distance between the plates, the less is the capacity of a capacitor. Variable capacitors are commonly used by radiomen; their function is to vary the frequency in the circuit.

Fixed capacitors are used in telephone and radio work. 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; their advantage is their high capacity: it may be higher than 1,000 picofarad.

Besides, electrolyte capacitors are highly in use. They also have a very high capacity: it varies from 0.5 to 2,000 microfarad. Their disadvantage is that they change their capacity when the temperature changes. They can operate without a change only at temperatures not lower than -40° С.

Common troubles in capacitors are an open and a short. A capacitor stops operating and does not store energy in case it has a trouble. A capacitor with a trouble should be substituted by a new one.

 

 

 

 

3. Complete these sentences using the correct variant:

1. A capacitor is used

a) to supply voltage.

b) to increase the voltage output.

c) to store energy.

 

2. The main parts of a capacitor are

a) insulators only.

b) metal plates only.

c) metal plates and insulators between them.

 

1. The function of insulators is

a) to store energy.

b) to isolate the metal plates.

c) to prevent a short between the metal plates.

 

4. The capacity of a capacitor depends on

a) the size of the plates.

b) the distance between the plates.

c) the material of the insulators.

 

5. The capacity of a fixed capacitor

a) is constant.

b) is varied.

 

6. The plates of a variable capacitor

a) can be moved.

b) cannot be moved.

 

1. In order to charge a capacitor a voltage source is applied

a) to the metal plates.

b) to the insulators.

 

8. The greater the distance between the plates,

a) the greater is the capacity of a capacitor.

b) the less is the capacity.

 

9. Variable capacitors have

 a) air insulators.

b) paper insulators.

c) ceramic insulators.

 

10. Electrolyte capacitors have

 a) а very low capacity.

b) a very high capacity.

 

11. In case a capacitor has a trouble

a) it operates.

b) it stops operating.

 

Conductors and Insulators

Conductors are materials having a low resistance so that current easily passes through them. The lower the resistance of the material, the more current can pass through it.

The most common conductors are metals. Silver and copper are the best of them. The advantage of copper is that it is much cheaper than silver. Thus copper is widely used to produce wire conductors. One of the common functions of wire conductors is to connect a voltage source to a load resistance. Since copper wire conductors have a very low resistance a minimum voltage drop is produced in them. Thus, all of the applied voltage can produce current in the load resistance.

It should be taken into consideration that most materials change the value of resistance when their temperature changes.    

Metals increase their resistance when the temperature increases while carbon decreases its resistance when the temperature increases. Thus metals have a positive temperature coefficient of resistance while carbon has a negative temperature coefficient. The smaller is the temperature coefficient or the less the change of resistance with the change of temperature, the more perfect is the resistance material.

Materials having a very high resistance are called insulators. Current passes through insulators with great difficulty. The most common insulators are air, paper, rubber, plastics. Any insulator can conduct current when a high enough voltage is

applied to it. Currents of great value must be applied to insulators in order to make them conduct. The higher the resistance of an insulator, the greater the applied voltage must be.

When an insulator is connected to a voltage source, it stores electric charge and a potential is produced on the insulator. Thus, insulators have the two main functions:

1. to isolate conducting wires and thus to prevent a short between them and

2. to store electric charge when a voltage source is applied.

 

3. Find answers to these questions in the text above:

1. What materials are called conductors?

2. What is the advantage of copper compared with silver?

3. What is the most common function of wire conductors?

4. Why is a minimum voltage drop produced in copper conductors?

5. What is the relation between the value of resistance and the temperature

in carbon?

6. What materials are called insulators?

7. What are the most common insulators?

8. What are the two main functions of insulators?

 

4. Complete the sentences using the correct variant:

 

1. Insulators are materials having

a) low resistance.

b) high resistance.

 

2. Current passes through conductors

a) easily.

b) with great difficulty.

 

3.Copper and silver are

a) common conductors.

b) common insulators.

 

4. Air, paper and plastics are

a) common insulators.

b) common conductors.

 

5. In case a high voltage is applied to an insulator

a) it does not conduct current.

b) it conducts current.

 

6. Insulators are used

a) to store electric charge.

b) to reduce voltage.

c) to prevent a short between conducting wires.

 

7. Metals increase their resistance

a) when the temperature decreases.

b) when the temperature increases.

 

5. Complete the sentences using while.

1. Conductors have a low resistance..........

2. Current passes through insulators with great difficulty..........

3. Metals are common conductors..........

4. To make insulators conduct, currents of great value must be applied

5. Carbon decreases its resistance when the temperature increases....

6. Metals have a positive temperature coefficient of resistance....

 

Lesson 9. Transformers

1. Read and learn the words:

core - сердечник

winding - обмотка

turn - виток

to step up - повышать

to step down понижать

frequency - частота

due to - благодаря, из-за

 

Transformers

A transformer is used to transfer energy. Due to the transformer electric power may be transferred at a high voltage and reduced at the point where it must be used to any value. Besides, a transformer is used to change the voltage and current value in a circuit.

A two-winding transformer consists o f a closed core and two coils (windings). The primary winding is connected to the voltage source. It receives energy. The secondary winding is connected to the load resistance and supplies energy to the load. The value of voltage across the secondary terminal depends on the number of turns in it. In case it is equal to the number of turns in the primary winding the voltage in the secondary winding is the same as in the primary.

In case the secondary has more turns than the primary the output voltage is greater than the input voltage. The voltage in the secondary is greater than the voltage in the primary by as many times as the number of turns in the secondary is greater than the number of turns in the primary.

A transformer of this type increases or steps up the voltage and is called a step-up transformer. In case the secondary has fewer turns than the primary the output voltage is lower than the input. Such a transformer decreases or steps down the voltage, it is called a step-down transformer.

Compare T₁ and T₂ in the diagram. T₁ has an iron core. For this reason it is used for low-frequency currents. T₂   has an air core and is used for high frequencies.

Common troubles in transformers are an open in the winding, a short- between the primary and the secondary, and a short between turns. In case a transformer has a trouble it stops operating or operates badly. A transformer with a trouble should be substituted.

 

3. Complete the sentences using the correct variant:

 

1. A transformer is used

a) to store charge.

b) to prevent the change of energy.

c) to transfer energy.

d) to change the voltage and current value in a circuit.

 

2. Electric power is transferred at a high voltage and reduced to any value

a) due to resistors.

b) due to capacitors.

c) due to transformers.

 

3. A transformer consists of

a) cores only.

b) the primary and the secondary windings.

c) a core and the primary and the secondary windings.

 

4. The function of the primary is

a) to prevent the change of voltage.

b) to supply energy.

c) to receive energy.

 

5. The function of the secondary is

 a) to receive energy,

b) to supply energy.

c) to transfer energy.

d) to decrease the value of charge.

 

6. A step-up transformer is

a) to step down or decrease the secondary used voltage.

b) to step up or increase the primary voltage

 

7. A step-down transformer is used

 a) to step down the secondary voltage,

b) to step down the primary voltage.

8. A transformer with an

a) is used for high-frequency currents, iron core b) is used for low-frequency currents.

9. A transformer with an air

a) for high-frequency currents and for lowcore is used frequency currents.

b) for high-frequency currents only.

 

10. In a step-up transformer

a) the number of turns of the secondary winding is greater than the number of

turns of the primary,

b) the number of turns of the primary winding is greater than the number of

turns of the secondary.

 

11. A transformer should be substituted

a) in case it has an open in the winding,

b) in case it has a short between the primary and the secondary,

c) in case it has a short between turns.

 

Types of Current

Current is a flow of electricity through a circuit. Let us consider two main types of current: direct and alternating. A direct current (d.c.) flows through a conducting circuit in one direction only. It flows provided a direct voltage source is applied to the circuit.

An alternating current (a.c.) 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 called the frequency of the current. In a 60-cycle alternating current circuit the current flows in one direction 60 times and in the other direction 60 times per second.

It is easy to transform a.c. power from one voltage to another by a transformer. Transformers are also used to step down the voltage at the receiving point of the line to the low values that are necessary for use.

When necessary a.c. can be changed into d.c. but this is seldom necessary.

 

3. Complete the sentences using the correct variant:

1. D.c. is a current that

a) changes its direction of flow.

b) flows in one direction.

 

2. A.c. flows provided

a) a direct voltage source is applied.

b) an alternating voltage source is applied.

 

3. In an alternating current circuit

a) current flows in one direction 60 times per second.

b) current flows in one direction 60 times and in the other direction 60 times per second.

 

4. A.c.

a) can be changed into d.c.

b) cannot be changed into d.c.

 

4. Answer the following questions:

 

1. What is current?

2. What types of current do you know?

3. When does a direct current flow?

4. What type of current is called an alternating current?

5. What type of current is called a direct current?

6. What is called the frequency of current?

7. What device is used to transform a.c. power from one voltage to another?

S. Is it often necessary to change a.c. into d.c.?

 

Lesson 1 2. Coupling

 

1. Read and learn the words:

 

Device -  прибор

field -  поле

loose - свободный, нежесткий

tight - плотный

self-inductance - самоиндукция

to couple - соединять, сцеплять

to separate - отделять

to transfer - переносить

therefore - поэтому

Coupling

When circuits are indirect-inductively coupled energy is transferred from one circuit to another using electromagnetic field of the inductance through which a varying current is flowing.

The coupling device is a transformer. It is not in series with the elements of the circuit, therefore the coupling is indirect. The transformer consists of two windings: the primary and the secondary. The primary circuit is connected to the voltage source, the secondary - to the load circuit. The coupling may be tight and loose. In case the coils of the coupling element are close together, the coupling is tight.

In case the coils are separated the coupling is loose. In the loose coupling the mutual inductance is small compared with the self-inductance.

 

3. Complete the sentences using the correct variant:

1. The circuit connected to the voltage source is called

a) the secondary circuit.

b) the primary circuit.

 

2. The circuit receiving its energy through a coupling is

a) the primary circuit.

b) the secondary circuit.

 

3. The function of a coupling element is

a) to separate the circuits.

b) to transfer energy.

c) to prevent a short between the circuits.

 

4. When the coupling is tight

a) the coils are separated.

b) the coils are close together.

 

5. When the coils are close together

a) the coupling is loose.

b) the coupling is tight.

 

6. The circuits are indirectly coupled when

a) the coupling element is common to both circuits and is in series with their

other elements.

b) the coupling element is not common to the circuits and is not in series with

their other elements.

 

4. Complete these sentences using while.

1. The circuit receiving energy is the secondary circuit....

2. The coupling is loose when the coils are separated..........

3. When the coupling element is not common to the circuits and not in series

with their elements, the circuits are indirectly coupled..........

 

5. Answer the following questions:

 

1. What type of circuit is called the primary?

2. What type of circuit is called the secondary?

3. What is the function of a coupling element?

4. What type of coupling is called loose?

5. What type of coupling is called tight?

6. In what case are the circuits directly coupled?

7. In what case are the circuits indirectly coupled?

8. What is the difference between a tight and loose coupling?

9. In what case should a coupling element be substituted?

 

Pair work.

 Draw a scheme of 1) a loose coupling, 2) a tight coupling.

Describe the schemes to your groupmate.

 

 

Lesson 1 3. Filters

 

1. Read and learn the words:

 

filter - фильтр

bypass - шунт

choke - дроссель

high-pass - высокопроходной

low-pass - низкопроходной

to oppose - оказывать сопротивление

on the other hand - с другой стороны

choke coil - дроссельная катушка

bypass coil - шунтовая катушка

bypass condenser - шунтирующий конденсатор

high-pass filter - фильтр верхних частот

low-pass filter - фильтр низких частот

opposing coils - противодействующие витки

opposed current – противоток

Filters

This filter is used to separate direct current from alternating current. It consists of a capacitor and a choke coil. Direct current cannot flow through the capacitor since its insulators oppose the flow of direct current. Therefore, it flows through the choke coil. Its windings easily pass direct current through them. Alternating current, on the other hand, passes through the capacitor, since it cannot easily pass through the choke coil. In this way the direct and the alternating currents are separated.

I. A high-pass filter is used to pass high frequencies and to prevent the flow of low frequencies. It consists of a condenser and an inductance coil. The condenser passes currents of high frequencies and opposes the flow of low frequency currents. Low frequencies must be returned to the source and the inductance coil is used for a bypass.

II. A low-pass filter is used to pass low frequencies and to prevent the flow of high frequencies. It consists of an inductance coil and a condenser. The inductance coil passes low frequencies and opposes the flow of high frequencies. To return the high frequencies back to the source, a condenser is used for a bypass. Its capacity opposes the flow of low frequencies through it.

 

Lesson 1 4. Electron Tubes

 

1. Read and learn the words:

tube - электронная лампа

bulb - баллон

grid - сетка

screen - экран

to contain -  вмещать

to collect -  собирать

to emit - излучать

to suppress - глушить, подавлять

control circuit - контрольная цепь

control grid - управляющая сетка

screen grid - экранирующая сетка

screen grid tube - экранированная лампа

suppressor grid - защитная сетка

counter flow - противоток

oscillatory circuit - колебательный контур

Electron Tubes

Let us consider electron tubes. Among the electron tubes in use nowadays there are a diode, a triode, a tetrode and a pentode. The main parts of electron tubes are electrodes. Electrodes are placed into a glass or metal bulb.

A diode contains the cathode and the plate. When a diode operates the cathode emits electrons, the plate collects them.

A triode contains the cathode, the plate and the control grid. When the tube operates the cathode emits electrons, the plate collects them and the grid controls the flow of electrons. Therefore, the grid is called a control grid.

A tetrode contains the cathode, the plate, the control grid and the screen grid.

When a tube operates it may oscillate. The function o f the screen grid is to eliminate oscillations. Therefore it is called a screen grid.

A pentode contains two electrodes and three grids: the control grid, the screen grid and the suppressor grid. When a pentode operates the suppressor grid eliminates the secondary emission.

Common troubles in tubes are an open heater and low emission. These troubles result from constant use or from some other reason.

In case a tube has a trouble it stops operating or operates badly. A tube with a trouble should be replaced by another one.

 

3. Complete the sentences using the correct variant:

 

1. A pentode contains

a) the cathode, the plate, two screen grids and the suppressor grid.

b) the cathode, the plate, the control grids, the screen grid and the suppressor grid.

 

2. A tetrode contains

a) the cathode, the plate, the suppressor grid and the screen grid.

b) the cathode, the plate, the screen grid and the control grid.

 

3. A triode contains

a) the cathode, the plate and the screen grid.

b) the cathode, the plate and the control grid.

 

4. The function of the cathode is

a) to collect electrons.

b) to eliminate the secondary emission.

c) to emit electrons.

 

5. The function of the plate is

a) to eliminate oscillations.

b) to emit electrons.

c) to collect electrons.

 

6. The function of the control grid is

a) to emit electrons.

b) to control the electron flow.

c) to eliminate secondary emission.

 

7. The function of the screen grid is

a) to collect electrons.

b) to reduce the capacity.

c) to eliminate oscillations.

 

8. The function of the suppressor grid is

a) to control the electron flow,

b) to eliminate secondary emission.

c) to eliminate oscillations.

 

9. Constant use of a tube results in

a) high emission,

b) low emission.

c) an open heater.

 

4. Answer the following questions:

 

1. What types of electron tubes are used nowadays?

2. How many electrodes does a diode (a triode, a tetrode, a pentode) contain?

3. What is the function of the cathode (the plate, the control grid, the screen grid, the suppressor grid)?

4. What does the constant use of a tube result in?

5. What does low emission result from?

6. When must a tube be replaced?

 

Pentode

When in an operating tube the screen-grid voltage is high, secondary emission does not return to the plate and passes to the screen grid. This results in a counter flow of electrons. To eliminate this counter flow, a third grid was placed between the plate and the screen grid and connected to the cathode. This grid is called a suppressor grid. Since the suppressor grid has a negative potential it returns the secondary emission back to the plate and thus eliminates it in the tube. The tube containing electrodes - the cathode, the plate, the control grid, the screen grid and the suppressor grid - is called a pentode. The cathode emits electrons, the plate collects them, the control grid controls the flow of electrons, the screen grid helps the plate to collect electrons and reduces the capacity between the control grid and the plate, the suppressor grid eliminates the secondary emission.

 

Use of Electron Tubes

Let us consider some cases of electron tube application. Tubes are common elements of radio and electronic devices. Tubes are used as rectifiers - to convert a.c. into d.c., as oscillators - to produce oscillating waves and as amplifiers - to amplify the input voltage and current.

Half-Wave Rectifier

Alternating current is converted into direct current by means of a rectifier.

A half-wave rectifier consists of a diode in series with a resistance. In order to put a rectifier into operation, a source of a.c. should be applied to it. When an a.c. source is applied the diode begins to conduct.

The rectifier passes currents during positive half-cycles of the applied voltage. That is why it is called a half-wave rectifier. When the device operates d.c. flows in the same direction. It is a pulsating current. Since pulsations should be  eliminated, a filter is applied. Pulsations are eliminated by means of this filter.

 

3. Complete the sentences using the correct variant:

1. Electron tubes are used

a) as amplifiers only.

b) as oscillators only.

c) as rectifiers, amplifiers and oscillators.

 

2. A.c. is converted into d.c.

 a) by means of a rectifier.

b) by means of an amplifier.

 

3. A half-wave rectifier consists of

a) a diode in series with a transformer.

b) a diode in series with a resistor.

 

4. In order to put a rectifier into operation

a) d. c. is applied.

b) a.c. is applied.

 

5. A half-wave rectifier passes currents

a) during positive and negative half-cycles.

b) during positive half-cycles of the applied voltage.

 

6. Rectified current is

a) direct oscillating current.

b) direct pulsating current.

 

7. Pulsations are eliminated

a) by means of a choke coil.

b) by means of a filter.

 

4. Answer the following questions:

1. How are electron tubes used?

2. What type of device is called a rectifier?

3. By what means is alternating current rectified into direct current?

4. What elements does a half-wave rectifier consist of?

5. What current should be applied to put a half-wave rectifier into operation?

6. When does a half-wave rectifier pass current?

7. By what means are pulsations eliminated?

 

Read and learn the words:

End - конец, конечный

Tap - отвод, ответвление

Filament - нить накала

Lower - нижний

Upper - верхний

Secondary - вторичный

end capacity - конечная емкость

end coils - концевые витки

filament battery - батарея накала

filament current - ток накала

secondary circuit - вторичный контур

secondary resistance - дополнительное сопротивление

secondary battery - аккумуляторная батарея

frequency waves - длинные волны

Full-wave Rectifier

In a full-wave rectifier two diodes are used. They are connected to a common load resistance. The secondary of the transformers has a centre tap to which the load is connected. Current flows through the tubes from their plates to their cathodes. When the upper end of the highvoltage winding is positive, current flows through the upper tube.

During the opposite half cycle the lower end of the high voltage winding becomes positive. The plate of the lower tube becomes positive and the plate of the upper tube - negative. Thus now the lower tube conducts current. Current flows through the filament winding to its centre tap, then through the load to the centre tap of the high-voltage winding and to the tube plate which is positive.

3. Complete the sentences using the correct variant:

 

1. A full-wave rectifier contains

a) one diode.

b) two diodes.

 

2. The load is connected to

a) the centre tap of the primary.

b) the centre tap of the secondary.

 

3. Current flows through the tubes

a) from the plates to the cathodes.

b) from the cathodes to the plates.

 

4. When the upper end of the highvoltage winding is positive

a) current flows through the upper tube.

b) current flows through the lower tube.

 

5. During the negative half-cycle

a) the plate of the lower tube becomes positive.

b) the plate of the lower tube becomes negative.

 

6. During the positive half-cycle

a) the lower tube conducts current.

b) the upper tube conducts current.

 

4. Complete the sentences using while.

 

1. A half-wave rectifier contains one diode..........

2. When the upper end of the high-voltage winding is positive, current

flows through the upper tube..........

3. During the negative half-cycle the lower tube conducts current..........

 

5. Pair work. Put these questions to your groupmate and let him/her answer them.

 

1. How many diodes does a full-wave rectifier contain?

2. What element is the load connected to?

3. What is the direction of current in the tubes?

4. During which cycle does the plate become negative?

5. When does the lower tube conduct current?

6. When does the upper tube conduct current?

7. What is the difference between a half-wave and a full-wave rectifier?

8. What is the difference in their construction?

9. In what way does a full-wave rectifier operate?

10. In what way does a half-wave rectifier operate?

11. What are the main parts of a half-wave rectifier?

12. What are the main parts of a full-wave rectifier?

 

Read and learn the words:

  to feed (fed) - питать

to include - содержать, заключать (в себе)

to remain - оставаться

to push - толкать

to pull - тянуть

push-pull - пушпул, пушпульный

push-pull amplifier - двухтактный усилитель

push-pull circuit - двухтактная схема

push-pull transformer - пушпульный трансформатор

feedback - обратная связь

feedback amplifier - регенеративный усилитель

feedback coil - катушка обратной связи

feeding transformer - силовой трансформатор

Push-pull Amplifier

An amplifier is used to produce the output voltage greater than the input voltage. A push-pull amplifier includes two tubes. Their control grids are connected to the opposite ends of the input transformer secondary winding. The centre of this winding is connected to the tube cathodes. When maximum grid voltage is produced in one tube, minimum grid voltage is produced in the other tube. Thus, the sum of the plate currents remains constant.

The plate currents are fed into the opposite ends of the output transformer or a choke coil. It has its centre connected through the plate current supply to the cathodes. Thus direct current plate components are eliminated but alternating current components add in the circuit.

3. Complete these sentences, using the correct variant:

 

1. An amplifier is used

a) to separate a.c. from d.c.

b) to change the value of the input voltage.

 

2. The input voltage is increased

a) by means of a rectifier.

b) by means of an amplifier.

 

3. A push-pull amplifier includes

a) only one tube.

b) two tubes.

 

4. When maximum grid voltage is produced in one tube

a) maximum grid voltage is produced in the other tube.

b) minimum grid voltage is produced in the other tube.

 

5. The sum of the plate currents

a) changes.

b) remains constant.

 

6. D.c. components

a) are eliminated.

b) add in the circuit.

 

7. A.c. components

a) add in the circuit.

b) are eliminated.

 

4. Complete the sentences using while.

1. An amplifier is used to increase the value of the input voltage..........

2. When maximum grid voltage is produced in one tube..........

3. Direct current plate components are eliminated.........

 

5. Answer the following questions:

 

1. What is an amplifier used for?

2. By what means is a greater output voltage produced?

3. What are the main parts of a push-pull amplifier?

4. In what way are the tubes and the transformer connected?

5. Why does die sum of the plate currents remain constant?

6. Where are the plate currents fed?

7. What type of current is amplified by a push-pull amplifier?

8. What is the difference between a rectifier and an amplifier?

6. Say a few words about an amplifier and a rectifier. What do they have in common? What is the main difference between them?

 

Read and learn the words:

 

bias - дополнительное (смещающее) напряжение

stage - каскад, ступень

to follow - следовать (за)

stage of amplification - ступень (каскад) усиления

grid bias - напряжение смещения

grid bias battery - сеточная батарея

grid plate capacitance - емкость анодной сетки

Amplifier Stages in Series

Amplifiers in use nowadays contain several stages. Sometimes their number is very great. Let us consider an amplifier including three stages. Its circuit uses three triodes connected in series. The circuit has a resistance as the plate load. A common plate voltage supply and a common grid bias are employed. The grid of each tube is insulated from the direct current component of the plate voltage by means of a capacitor. When the amplifier operates the voltage operation of the load

of one tube is applied to the grid of the next tube. The voltage variation is  transferred to the grid of the following tube through a capacitor. A change of  voltage on the first grid circuit results in an amplified plate current in the third stage.

 

3. Complete these sentences, using the correct variant:

1. Amplifiers in use nowadays

a) include only one stage,

b) include several stages.

 

2. A three-stage amplifier uses

a) three triodes connected in parallel.

b) three triodes connected in series.

 

3. The grid of each tube is insulated

a) by means of a coil.

b) by means of a capacitor.

 

4. The voltage variation is transferred

a) through a tube.

b) through a capacitor.

 

5. The circuit uses

 a) a different grid bias.

b) a common grid bias.

 

4. Answer the following questions:

 

1. How many stages do amplifiers include?

2. What are the main parts of a three-stage amplifier?

3. By what means are the grids of the tubes insulated?

4. What type of grid bias is employed?

5. In what way is the voltage variation transferred?

 

Read and learn the words:

 

Spring - пружина

cross-section - поперечное сечение

to close - замыкать, закрывать

close to - близко к (от)

to move - двигаться, приводить в движение

to switch on - включать

to switch off - выключать

various - различный, разнообразный

 

Electromagnetic Relay

Electromagnetic devices called relays are widely used in various branches of industry.

The main parts of a relay are an electromagnet, a spring and an armature. When a current starts flowing in the electromagnet winding, the armature moves and the spring closes the contacts. The primary circuit o f a relay is its electromagnet circuit and the secondary circuit is the one closed by the contacts.

When there is no current in the relay’s primary circuit, the spring pulls the  armature and the contacts open.

Fig. shows how a 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 will stop when the relay opens.

Without a relay, conductors with a large cross-section would have to be brought to the motor. This would be very uneconomical. The current in a relay is tens and even thousands of times smaller than that used to power the motor. Therefore, the connecting wires can have small crosssections. In many systems the relay primary circuit operates automatically. Every evening and morning street lights are switched on and off from the main control panel by means of a great number of relays.

3. Complete the sentences using the correct variant:

 

1. The main parts of a relay are

a) an electromagnet, a capacitor, and a spring,

b) an electromagnet, an armature, and a spring.

 

2. When current starts flowing

a) the spring opens the contacts,

b) the spring closes the contacts.

 

3. The spring pulls the armature

a) when there is current in the primary circuit,

b) when there is no current in the primary circit

 

4. The wires connecting the panel with the relay

a) have a large cross-section,

b) have a small cross-section.

5. Street lights are switched on and off

a) by means of relays.

b) by means of electric motors.

 

4. Complete these sentences using while.

 

1. The primary circuit of a relay is its electromagnetic circuit..........

2. When there is no current in the relay’s primary circuit the contacts open...........

3. Without a relay conductors with a large cross-section should be used

4. Every evening street lights are switched on..........

 

5. Answer the following questions:

 

1. What are the main parts of a relay?

2. How is a relay put into operation?

3. When does the spring pull the arm