Учебное пособие по английскому языку для студентов факультета «Автомобильный транспорт», обучающихся по специальности «Электрооборудование автомобилей и тракторов» icon

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И. В. Бреус, М. С. Минина




The Principles of Electronics

and Electrical Engineering




ОСНОВЫ ЭЛЕКТРОНИКИ

И ЭЛЕКТРОТЕХНИКИ


Омск  2009


Федеральное агентство по образованию

ГОУ ВПО «Сибирская государственная автомобильно-дорожная

академия (СибАДИ)»


И. В. Бреус, М. С. Минина


The Principles of Electronics

and Electrical Engineering


ОСНОВЫ ЭЛЕКТРОНИКИ

И ЭЛЕКТРОТЕХНИКИ


Учебное пособие по английскому языку

для студентов факультета

«Автомобильный транспорт», обучающихся

по специальности «Электрооборудование

автомобилей и тракторов»


Омск

СибАДИ

2009

УДК 811.11: 629.331

ББК 81.432.1: 39.3

З 97


Рецензенты:

канд. пед. наук, доц. кафедры иностранных языков

ИВМ ОмГАУ Т.А. Завелева;

канд. пед. наук, доц., зав. каф. спец. языковой

подготовки ОмГАУ Т.М. Ежкина


Работа одобрена редакционно-издательским советом академии в качестве учебного пособия.


^ Бреус И.В., Минина М.С.

З 97 The Principles of Electronics and Electrical Engineering. Основы электроники и электротехники: учебное пособие по английскому языку для студентов факультета «Автомобильный транспорт», обучающихся по спе-циальности «Электрооборудование автомобилей и тракторов» / И.В. Бреус, М.С. Минина. – Омск: СибАДИ, 2009. – 112 с.


ISBN 9785932044629


Учебное пособие содержит упражнения и тексты для студентов I, II курса факультета «Автомобильный транспорт», обучающихся по специальности «Электрооборудование автомобилей и тракторов». Тексты и упражнения способствуют знакомству с будущей специальностью студентов и направлены на развитие навыков профессионального чтения, говорения.

Библиогр.: 10 назв.


ISBN 9785932044629  ГОУ «СибАДИ», 2009


PART I


^ ELECTRICITY AND MAGNETISM


Text 1

1. Прочтите и переведите текст. Кратко передайте его содержание на английском языке.


NATURE OF ELECTRIC CURRENT


In the modern conception of the constitution of matter it is composed of atoms. The atom is made up of a positive nucleus surrounded by negative charges of electricity, called electrons, which revolve about the nucleus at tremendous speeds. The nucleus consists of a number of protons, each with a single positive charge, and, except for hydrogen, one or more neutrons, which have no charge. The atom is neutral when it contains equal numbers of electrons and protons. A negativly charged body contains more electrons than protons. A positivly charged body is one which contains fewer electrons than its normal number.

When the two ends of a conductor are connected to two points at a different potentials, such as the terminals of a battery, we say that there is an electric current in the conductor. What actually happens?

The conductor has equal numbers of positive and negative charges in its atoms, and we want to know how the charges can be made to produce a current. The atoms in metals are packed so closely that they overlap to some extent, so that it is comparatively easy for the outer electrons to pass from one atom to another if a small force is applied to them. The battery causes a potential difference between the ends of the wire, and thus provides forces that make the negative electrons in the wire move toward the point of higher potential. This electron flow toward the positive electrode is the electric current. Naturally materials differ considerably in the ease with which electrons can be made to migrate from atom to atom.

The current will not flow unless there is an electric circuit. The magnitude of the current depends simply on the rate of flow of electrons along the conductor.


^ 2. Прочтите и выучите:


nucleus – ядро

charge – заряд

to revolve – вращаться

speed – скорость

hydrogen – водород

neutron – нейтрон

conductor – проводник

terminals – зажим, конец

battery – аккумулятор; батарея

current – ток, поток

outer – внешний, отдаленный (от центра)

to cause – причинять, вызывать

wire – проволока

circuit – схема; сеть; цепь

magnitude – величина; размеры


^ 3. Прочтите слова из текста и составьте 3 предложения:


conception, surround, neutral, except, equal, contain, potential, tremendous,

actually, comparatively, provide, toward, flow, migrate, apply, higher.

4. Ответьте на вопросы.


1. What is an atom? 2. When is the atom neutral? 3. What is a negativly charged body? 4. What is a positivly charged body? 5. What is an electric current? 6. What does the magnitude of the current depend on?


^ 5. Составьте предложения, используя слова и выражения:


a negativly charged body; from negative to positive; from one atom to another; a number of protons; a single positive charge; equal number and protons; to differ in the ease.


^ 6. Прочтите следующие диалоги и найдите английские экви-валенты следующим фразам:


ядро окружено; размышлять, обдумывать, наблюдать; количество отрицательных зарядов; зафиксированный результат наблюдений; на самом деле, в действительности; насколько мне известно; положительно заряженные частицы; если кусок янтаря потереть о мех; маятник; притягивать легкие предметы; позднее было обнаружено; общеизвестный факт; различные вещества; наиболее существенная составная часть вещества; кулон; единица измерения.


-1-


- When was the first recorded observation about electricity made?

- As far as I know it was made by the Greek philosopher Thales.

- What did he state, I wonder?

- Don’t you know? He stated that a piece of amber rubbed with fur attracted light objects such as feathers and bits of straw.

- Did he make any experiments?

- No, as far as it is known Thales liked to speculate but he did not experiment systematically. Twenty two centuries elapsed before there was any progress.

- Oh, it was just about the time that Galileo discovered the laws of the pendulum and accelerated bodies. So it was at the time when the study of magnetism and of electrical phenomena began.


-2-


- How was it found out that some substances can be “electrified”?

- It is a well-known fact that having been rubbed many substances behaved like amber did.

- Can only similar substances become electrified or acquire electrical charges, being touched together and then separated?

- No. Later on it was discovered that any of two dissimilar substances could be electrified. As a matter of fact rubbing is not essential. It merely forces the two substances into close contact.


-3-


- What do you know about the nucleus, the proton and the electron?

- In the electrical system there is a nucleus containing positively charged particles. These particles are called protons. The nucleus is surrounded by lighter negatively charged units – electrons. So, the most essential constituent of matter is made up of electrically charged particles.

- When matter is neutral?

- Everybody knows that matter having equal amounts of both charges is neutral - that it produces no electrical effects.

- And what happens if the number of negative charges is unlike the number of positive ones?

- Well, then the matter will produce electrical effects. Having lost some of its electrons, the atom has a positive charge; having an excess of electrons – it has a negative charge.

- So, as a matter of fact you do know the material.

-4-


- When will electrons move?

- If given a path, electrons dislodged from the parent atom, will move.

- Well, what do you know about the electric current?

- The electric current is a quantity of electrons flowing in a circuit per second of time.

- And what is the unit of measure for current?

- The unit of measure for current is the ampere. One coulomb passing a point in a circuit per second, the current strength is 1 ampere. The apmere is therefore a rate unit.


7. Дайте полное описание природе электрического тока.


Text 2


1. Прочтите и переведите текст.


^ ELECTROMOTIVE FORCE


When free electrons are dislodged from the atoms, electrical energy is released and made available to do work. Chemical reaction, friction, heat and electromagnetic induction will cause electrons to move from one atom to another. Scientists proved electrical energy to be released from matter by chemical reaction (batteries), heat (thermocouples), electromagnetic induction (generators), and friction (static generators). Whenever energy in ahy form is released, a force is developed. Electrical energy being released, a forec called electromotive force (e.m.f.) is developed. And e. m. f. is present, then, whenever free electrons are moved from atoms, any of the abovenamed methods being used to produce such electron motion.

If the force exerts its effort always in one direction, it is called direct; the force changing its direction of exertion periodically is referred to as alternating.

The chemical reaction in a dry cell produces a negative charge or potential on the zinc. This charge being always negative, the e.m.f. is uninderectional (one way). Heat and friction, too are sources of a undirectional force. Elecromagnetic induction, however, is certain to produce an alternating force.

If the south of a bar magnet (see the figure) is passed into a coil of wire connected to a force-measuring instrument (voltmeter), the meter needle will move in one direction. If the south pole of the magnet is withdrawn from the coil, the needle will move toward the opposite side of the meter, thus showing the force to be alternating. The direction of force effort is seen to be dependent upon the direction in which the field is cut. The magnitude of the elecrical force depends on the conditions at the source, such as the number of magnetic lines of force per unit of time.

In the battery, the determing factors are kinds of electrolytes and the kind of the metals to be used for the plates. The common dry cell is found to develop 1.5 volts of electrical force regadless of the size of the cell. Large amounts of force can be obtained only by putting many cells in series.

The force developed by the generator depends on the number of coils in the armature, on the speed of the armature, and on the strength of the magnetic field from the field magnets, i.e., the number of lines of magnetic force cut by a coil per second. The volt is known to be the unit of measure for electrical force.

Wherever an e. m. f. is developed, there is also a field of energy called an electroststic field. This field can be detected by an electroscope, the strength being measured by an electrometer.


^ 2. Прочтите и выучите:

termocouple – термопара, термоэлемент

induction – индукция

e. m. f. – electromotive force – электродвижущая сила

alternating – переменный, синусоидальный (о токе)

cell – элемент

zink – цинковая пластина (аккумуляторной батареи)

uninderectional – однонаправленный

bar magnet – полосовый магнит

coil – катушка

needle – игла, стрелка (прибора)

armature – якорь (магнита или машины)

meter – счетчик; измерительный прибор

plate – анод, пластина, полоса

in series – последовательно


^ 3. Прочтите слова из текста и составьте 3 предложения:


measure, methods, heat, friction, obtain, electrolyte, source, figure, south, field, however, exertion.


4. Найдите в тексте синонимы следующим словам:


to make, substance, to name, force, to indicate, movement, to receive, amount, since, usual, to apply, velocity, dimension, to definу.


^ 5. Дайте английские эквиваленты следующим словам:


зависеть от, заставлять, при этих условиях, за единицу времени, всякий раз когда, где бы ни, независимо от, иметься в наличии, вышеупомянутый, по отношению к, больше чем.


^ 6. Найдите конструкции с инфинитивом в следующих предло-жениях и переведите предложения на русский язык:


1. A compensator allows the motor to take an exess current without putting a heavy overload on the mains. 2. We know water to flow with less resistance in a large pipe than in one of small section. 3. If we double the force pushing the electrons around the circuit, we expect them to move twice as fast, all other things being equal. 4. To produce a current of one ampere in a copper wire one millimeter in diameter we need that the average velocity of the electrons be only about 001 cm. per second. 5. The only way to stop or control the anode current is to decrease or remove the anode voltage. 6. When the temperature becomes high enough for the atoms to evaporate, the material or solid that they compose rapidly disintegrates. 7. A conducting material allows a continuous current to pass through it under the action of a continuous e. m. f. 8. To measure current we use an ammeter connected in series with the resistance. 9. The action of an e. m. f. causes electrons to move in some definite direction. 10. To break the electron loose from its atom the force tending to move it is not sufficient.


^ 7. Обсудите одну из следующих тем:


1. Different methods of releasing electrical energy from matter. 2. The development of the electromotive force. 3. The direction of the e. m. f. 4. Batteries as a source of electrical energy. 5. The force developed by the generator. 6. The electrostatic field.


Text 3


1. Прочтите текст. В каждом абзаце подчеркните ключевое предложение.


^ FLOW OF ELECTRICITY


Whenever an electric field is set up in a substance by any means whatever a displacement of the electricity in that substance always takes place, the nature of the displacement depending upon the nature of the substance. In every case the positive electricity within the substance is displaced in the direction of the field intensity, the negative electricity being in the opposite direction, until an opposing force of some kind is set up which just balances the forces due to the impressed field.

Conductors of electricity. According to electronic theory, the electron is responsible for a flow of current of electricity. Good conductors are considered to be those substances in which there are present free electrons in constant but indiscriminate motion between the atoms. Under the action of an electromotive force, these free electrons move in some definite direction, resulting in a constant stream of electrons flowing at a phenomenally rapid rate in the conductor. In the case of a uni-directional or direct current, this electronic stream is always in one direction, while with alternating current the electronic stream reverses its direction of motion with regular frequency. All pure metals are good conductors of electricity, silver being the best since it offers the least resistance to a flow of current of electricity. We know copper to be very nearly as good a conductor as silver and, being very much cheaper, it is extensively used for electrical apparatus of all kinds. It is universally employed in all automobile electrical equipment.

Roughly speaking a conductor is a body which readily permits the passage of an electric current, an insulator being a body which offers a very high resistance to the passage of the current. As a matter of fact, there is no sharp distinction between conductors and insulators, however, a material which for some cases would be regarded as an insulator would, in other circumstances, be regarded as a conductor. A substance which is a good insulator at law temperatures may be a fair conductor at high temperatures.

Glass is the most striking illustration of this change of character with the change of temperature; at ordinary temperature it ranks high with the very best insulators. If glass be heated in some way to a red heat, it becomes a fair conductor and will permit the passage of enough current to melt itself.


^ 2. Прочтите и выучите:


uni-directional – однонаправленный

indiscriminate – беспорядочный, смешанный

insulator – изолятор


3. Прочтите текст повторно и выпишите ключевые слова и словосочетания, составляющие тематическую основу текста.


^ 4. Прочтите и переведите следующие слова:


responsible – responsibility, accessible – accessibility, possible – possibility, applicable – applicability, measurable – measurability, available – availability.

5. Переведите следующие пары слов, обращая внимание на значение приставок mis, dis, un, im, in, ir :


to use – to misuse, to match – to mismatch, to cover – to discover, to appear – to disappear, usual – unusual, common – uncommon, perfect – imperfect, possible – impossible, dependent – independent, discriminate – indiscriminate, regular – irregular, respectively – irrespectively, legal – illegal.


^ 6. Укажите прилагательные и наречия в приведенном списке слов:


substance, force, motion, stream, rapid, rate, since, nearly, extensively, to employ, readily, good, ordinary, permit, determination, electrical, striking, high, some, impressed.


^ 7. На английском языке опишите свойства:


a) conductors of electricity; b) insulators.


8. Используя материал текста, ответьте на вопросы.


1. What is responsible for a flow of current of electricity? 2. What substances are considered to be good conductors of electricity? 3. When do free electrons move in some definite direction and what is the result of this movement? 4. What is the stream of electrons both in a direct and alternating current? 5. At what frequency does the electronic stream reverse its direction of motion? 6. What are the best conductors of electricity? 7. What is an insulator? 8. Is there any sharp distinction between conductors and insulators? 9. What can be said about glass in this respect?


^ 9. Прочтите следующий диалог. Составьте диалог по аналогии с образцом в рамках данной устной темы:

а) но в иной ситуации;

б) при ином характере общения;

в) смене собеседников;

г) с иной задачей общения.


^ CONDUCTORS AND INSULATORS


Demonstrator: What substance is a conductor of electricity?

Student: Any substance or material which will afford continuous passage of an electric current when subjected to a difference of electric potential is a conductor of electricity.

Demonstrator: When is a conductor said to be more efficient?

Student: The greater the density of current for a given potential difference the more efficient the conductor is said to be.

Demonstrator: What substances are efficient conductors and which are poor ones?

Student: Virtually all substances in solid or liquid state possess the property of electric conductivity in some degree. The metals, for example, are the best conductors, many other substances, such as metal oxides and salts, minerals and fibrous materials being relatively poor conductors of electricity.

Demonstrator: Which of less efficient conducting materials are of great use in electricity?

Student: Some of the less efficient conducting materials such as carbon and certain metal alloys have very useful applications in electrecal arts, as well as the efficient conductors such as copper and aluminum.

Demonstrator: What substances are classed as non-conductors?

Student: Certain substances are known to possess so little conductivity that they are classed as non-conductors, a better term being insulators or dielectrics.

Demonstrator: Define a conductor, please.

Student: A conductor is a body so constructed of conducting material that it may be used as a carrier of electric current. In ordinary engineering usage a conductor is a material of relatively high conductivity.

Demonstrator: Could you define a circuit, please.

Student: An electric circuit is the path of an electric current or, more specifically, it is a conducting part or a system of parts through which an electric current is intended to flow.


^ 10. Прочтите и выучите следующие слова:


density – плотность alloy – сплав, сплавлять

solid – твердый, сплошной dielectric – изоляционный

liquid – жидкий path – путь, траектория

fibrous – волокнистый application – применение

oxide – окись, окисел aluminum – алюминий

carbon – углерод conductivity – удельная проводимость,

электропроводимость


Text 4


1. Прочтите текст, разделите его на смысловые части, подберите названия к каждой из них.


^ DIFFERENCE BETWEEN CONDUCTORS AND INSULATORS FROM

THE ELECTRON VIEWPOINT


When a conductor is carrying an electric current, the electrons are moving gradually along through the substance of the conductor. Now in a solid body, such as a metalic conductor, the atoms or molecules comprising the substance are known practically to be fixed in position. They are not actually stationary in space at ordinary temperature, of course; as a matter of fact, the atoms have an irregular to-and fro-motion similar to that of the electrons. But there cannot be a progressive motion of the atoms as there may be of the electrons. The reason for this is more or less evident. Suppose a current to be flowing along a copper wire. The electrons move all the way around the circuit through the wire, connections, solution in the battery, etc.

The atoms of copper being charged positively after an electron has left them, it might seem that as the electrons move from И to A through the wire the atoms would move from A to B, then into and through the battery and so back to the wire. But the atoms are thу real substance of the wire, and hence if the atoms should progress one way or the other it would result in the copper itself being carried from one end of the wire to the other and then through the battery. This state of affairs is not possible in solid bodies like metals, it would result in the mixing of metalswherever a current left one metal and went into another.

In chemical solutions, e.g., copper sulphate in water, the salt molecule breaks up into two parts, one of which has one electron more than its proper number, the other part lacking one electron. The two parts of the molecule are called ions; the metallic ion (in above case, copper) lacks one electron and so is charged positively. If now a current is passed through such a solution, the metallic ion does move through the solution and is carried from the solution to one of the wires by which the current is led into the solution. Here copper itself is transported by the current and we have the process of electro-plating.

From what has been said it follows that the molecules of a body clinging to the electrons so tightly that none of them are free to move away from the molecule, there can be no current in such a substance. As long as the mplecule keeps all the electrons, it remains electrically neutral, and so has no tendency to move in an electric field. This is the essential difference between insulators and conductors; in one the electrons cannot move from the atom or molecule and in the other the electrons are perfectly free to leave the atom.

^ 2. Прочтите и выучите:


substance – вещество

stationary – неподвижный, стационарный, постоянный

irregular – неравномерный, неправильный

connection – связь, присоединение

solution – раствор, разрешение (вопроса, проблемы)

sulphate – сульфат, соль серной кислоты; sulphate of copper (of iron, of

zinc) медный (железный, цинковый) купорос

electro-plating – гальванопокрытие

cling – цепляться, прикреплять

tightly – плотно, без зазоров, тесно


^ 3. Найдите в тексте английские эквиваленты следующих слов:


такой, как; конечно; по сути; взад и вперед; причина этого в том; более или менее приводить к (чему-либо); где бы ни; например; пока; следовательно.


^ 4. Переведите с русского на английский язык, используя данные выражения to some degree (extent), the...the, both...and :


1. Все вещества в твердом или жидком состоянии обладают до некоторой степени электрической проводимостью. 2. Как проводники, так и изоляторы имеют очень широкое применение в электротехнике. 3. Чем больше приложенное напряжение, тем ярче свет электрической лампы.


^ 5. Переведите следующие предложения, обращая внимание на различные значения и употребление глагола to be :


1. Such an instrument as the moving iron attraction type is suitable for use with both alternating as well as direct currents. 2. It is necessary to take into account that some instruments have a scale which does not start at zero. 3. One method of detecting the presence of a current in a wire is to measure the rise in temperature of the wire due to the current. 4. Iron, nickel or other magnetizable substances are to be thought of as composed of molecules or groups of molecules each of which is a perfect little magnet with its two opposite magnetic poles. 5. There is always something of the nature of a resistance or opposition which has to be overcome. 6. The armature is at rest, and in the absence of any back e.m.f. the low armature resistance would allow a very heavy current to flow in it.

^ 6. Определите форму и функции герундия и переведите сле-дующие предложения:


1. Before switching on current for a test the circuit should be thoroughly checked over to see that it is in accordance with the circuit diagram, particular care being take that ammeters are not directly across the mains. 2. If the atom should progress one way or the other, it would result in the copper itself being carried from one end of the wire to the other and then through the battery. 3. On joining the upper ends of the metals with a metal wire we caused the current to flow through the wire. 4. The use of a cooling medium prevents the device from overheating. 5. The most common method of magnetizing permanent magnets is to insert the magnets in a suitable exciting coil and to cause a large current to flow in the coil. 6. The new method could be used with great advantage without the machine being overheated. 7. The meter being highly accurate is of the greatest importance for getting the necessary experimental data. 8. We know of silver and copper being very good conductors of electricity. 9. Breaking the circuit causes sparking as a result of the coil current flow. 10. Not stopping the machine will prevent too rapid cooling with subsequent freezing of the bearings or warping of the shaft. 11. The dynamomotor is compact, light and highly efficient because of the armature reaction being small. 12. When a bar of iron is thrust into a fire it becomes heated due to the atoms comprising the bar becoming agitated.


^ 7. Прочтите текст 4 еще раз и передайте его основную идею несколькими предложениями.


Text 5


1. Прочтите заглавие следующего текста и скажите, о чем, по вашему мнению, будет идти речь в тексте.


^ SOME FACTS ABOUT THE MAGNETS


Being heated a magnet loses some or all of its magnetism. A magnet being broken in two, each piece becomes a magnet with its own pair of poles. This subdivision could be carried on until we were down to the smallest particle of iron, a molecule. Conversely, two identical bar magnets being brought end to end with opposite poles in close contact, the poles touching seem to disappear and we have but two poles at the extreme ends. A tube of iron filings may be magnetizid by stroking it with a magnet in the usual way. The filings being shaken, the magnetism disappears.

These facts give rise to the very plausible theory of magnetism generally accepted. We know iron molecules to be magnets at all times. When they are arranged in a bar oа steel or iron so that the fields of force of all or most of the molecules are in the same direction, their fields are added to one another and the bar is a magnet. The little magnet molecules form chains, their poles disappearing except at the ends of the chain. This condition is not an equilibrium condition because of the like poles in adjacent chains repelling each other. The rigidity of steel holds the molecules in this position. In soft iron, however, as soon as we take the bar out of the magnetizing field, the molecules adjust themselves on account of the repulsions of like poles of molecules in adjacent chains, leaving the iron unmagnetized. We can see why hard steel makes permanent magnets and soft iron dors not.

We can also explain why soft iron has a higher permeability than steel. When placed in a magnetic field, the molecules of steel do not readily turn around in the direction of the lines of force. But this alignment is necessary if the body is to absorb lines of force. Heating which increases molecular motion, or jarring causes a magnet to be demagnetizid due to its permitting the molecules to adjust themselves to the equilibrium position.


^ 2. Прочтите и выучите:


bar magnet – полосовой магнит

filing – наполнитель, прокладка

plausible – вероятный, правдоподобный, благовидный

equilibrium – равновесие

adjacent – смежный, примыкающий, соседний

repel – отталкивать

rigidity – жесткость

pole – полюс, like (opposite(unlike)) poles – одноименные

(разноименные) полюсы

alignment – выравнивание, выверка, настройка, регулировка


^ 3. Составьте цепочку из основных фактов текста, в которой ключевые слова были бы связаны по смыслу.


4. Изучите следующие синонимичные группы слов и выражений. Составьте предложения, употребляя данные выражения:


conversely, on the contrary; under consideration, in question; at hand, in point; to meet the requirements, to fill the requirements; meet the demands,to fill the demands; thanks to, due to, owing to, because of, on account of, by virtue of.


^ 5. Найдите в тексте антонимы к следующим словам. Составьте с ними предложения:


to appear, different, to attract, hard, low, to decrease, to acquire, up, likewise, unlike.


6. Изучите употребление и значение слова take в различных комбинациях. Переведите следующие предложения:


1. The escape of neutrons from any quantity of uranium is a surface effect depending on the area of the surface, whereas fission action takes place throughout the body and is therefore a volume effect. 2. The varying current from the television takes the place of the voice currents from the microphone. 3. The discovery of the atomic battery may take its place alongside with nuclear reactors in providing the world with new sources of electricity. 4. Many radio amateurs take advantage of radio transmitters with one vacuum tube only. 5. It would take 100 million of small thimble sized atomic batterirs to produce enough electricity to light a 100-walt bulb, but its discovery is a very important one. 6. In atomic power plants special safety precautions must be taken to protect the workers from the danger of radioactivity. 7. It will take not very much time to see the widespread use of semiconductors in every-day life. 8. In metals conduction takes place through the motion of electrons.


^ 7. Прочтите текст повторно и ответьте на вопросы.


1. What happens to a magnet: a) when it is heated or broken in two? b) when two indentical bar magnets are brought end to end with opposite poles in close contact? 2. When does a bar become a magnet? 3. When do the molecules adjust themselves? 4. Why does hard steel make permanent magnets and why has soft iron a higher permeability than steel?


^ 8. Переведите на английский язык текст.


Нагревание магнита приводит к потере им магнетизма. Если разделить магнит на две части, то каждая из них остается магнитом, т.е. каждая часть будет иметь свою пару полюсов. И наоборот, если соединить два магнита, то в результате получится один большой магнит. Общепринятая теория магнетизма легко объясняет ряд очень интересных явлений. Например, почему твердая сталь обладает постоянными магнитными свойствами, в то время как мягкое железо лишено их. Также на основании этой теории можно объяснить более высокую магнитную проницаемость мягкого железа по сравнению со сталью.

^ 9. Прочтите диалог, восстанавливая отдельные реплики одного из собеседников.


ELECTROMAGNETISM


Demonstrator: What would happen if a freely suspended needle (compass) were brought near a conductor carrying a current?

Student: In this case the needle would tend to place itself at right angles to the conductor.

Demonstrator: Well, --------------------------------------------------------?

Student: This indicate that a field about the conductor is reacting upon the field about the magnetized needle.

Demonstrator: Why is the field ---------------------------------------------?

Student: We know the magnetic lines of force to tend not to cross over each other. That’s why, the field about the conductor must be of a circular nature.

Demonstrator: All right. And how is a stronger magnetic field about the conductor created?

^ Student: The conductor being wound into a coil, the fields about each tern combine and create a strong magnetic field.

Demonstartor: How ----------------------------------------------------------?

Student: If a piece of iron is placed in the coil, the iron will become magnetized by the electromagnetic field and an electromagnet is produced.

Demonstrator: When would the iron be demagnetized?

Student: If the electron flow through the coil ceased, the magnetic field would collapse and the iron would no longer be magnetized.

Demonstrator: What can you say about permeability and retentivity in soft iron and steel?

Student: Well, the soft iron has high permeability and low retentivity, while steel has low permeability and high retentivity.

Demonstrator: -------------------------------------!!!


^ 10. Прочтите и выучите следующие слова:


needle – игла, стрелка (прибора)

cease – прекращать (-ся), переставать, приостанавливать

collapse – рушиться, сплющиваться, обваливаться

permeability – проницаемость

retentivity – остаточный магнетизм


^ 11. Воспроизведите в ролях диалог, сократив его и используя только основную информацию.






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