от условий на поверхности эмиттера. Этот эмиттер должен быть в хорошем вакууме. Мы знаем, что вакуумные лампы широко используются в технике.
6 Lesson 6
6.1 Прочтите слова согласно транскрипции
cathode, filamentary, alternating, determine , winding, channel, ceramic, advantage, uniform, refer, unimpotential, close , otherwise, affect, contribute.
6.2 Прочтите слова, обращая внимание на смещение ударения
filament -filamentary; determine - determination; possible - possibility; metal - metallic; advantage -advantageous; contribute -contribution; magnet – magnetic
6.3 Сгруппируйте эквиваленты
to reduce fluctuation, result(in), close, advantage, to cause fluctuations, affect, hum, winding, alternating(current), direct(current)
переменный ток, вызывать флуктуации, постоянный ток, приводить(к), преимущество, сокращать флуктуации, близкий, воздействовать(на), помехи, обмотка
6.4 Сгруппируйте антонимы
heat , directly , frequently , increase , use , raise , internal , harm , cool , indirectly , seldom , decrease , lower , external
6.5 Прочтите и переведите текст
Physical construction of cathode
1. Two types of cathodes are employed in vacuum tubes ,the filamentary and the indirectly heated. The filamentary cathode consists of a wire filament, usually bent in the form of a V or a W, and is heated by the passage of a current; either direct or alternating, through it. If alternating current is used for heating, as is most frequently the case today the different parts of the cathode are not at constant potential, on account of the IR drop of this current. Since the electron stream is determined by the potentials of the other tube elements with respect to the cathode, this may cause fluctuations which result in the development of hum in the tube output. To reduce these fluctuations as much as possible, it is common practice to connect the return circuit from the other tube elements to a center tap on the transformer winding which supplies filament-heating current. This point is always at the average potential of the entire filament.
19
2 The indirectly heated cathode consists of a metallic sleeve coated with emitting substance, and is heated bywlraspassing through channels in a ceramic insulating core placed the sleeve. The advantage of this construction is that entire cathode is at a uniform potential, since it carries none of the heating current. It is therefore referred to also as a unimpotential cathode. Another advantage is that the heater wires are so close together that the current in them produces practically no magnetic field, which otherwise would also affect the electron flow and thereby contribute to the hum in the tube output.
6.6 Переведите словосочетания
a) wire filament, electron stream, tube elements, tube output, transformer winding, filament-heating current;
b) this may cause fluctuations; they result in the development of hum in the tube output; as much as possible; it is common practice
6.7 Ответьте на вопросы
1 What types of cathodes are employed in vacuum tubes? 2 What is common practice to reduce the fluctuations as much possible? 3. Where is a ceramic insulating core placed? 4. What is the advantage of the indirectly heated cathode?
6.8Переведите предложения
1Не would have connected these circuits much quicker.2This might cause fluctuations which would result in the development of hum in the tube output. 3. Were the temperature increased, the velocity of the molecular motion would be increased. 4. Had the filament been heated, we should have obtained the electron emission. 5. It is essential that the entire cathode should be at a uniform potential. 6. It is necessary that a means be provided for cooling the winding 7. Provided all the requirements were met, the effciency of the apparatus would be increased. 8. If alternating current were used for heating, the different parts of the cathode would not be at constant potential.
6.9Определите, какой частью речи являются слова
frequently, constant, possible, advantage, practically ;ceramic, transformer.
6.10 Прочтите диалог в ролях
Dialogue
A.I get excited at the thought that in a week I'll take my English exam.
B.I'm sure everything will be all right. You are good at languages and you have been working hard during this term.
20
A.By the way, our English teacher said that we should be asked questions on our specialty in English.
B. I think it would be very useful to practise some questions and answers before the exam.
A.That's an idea 'Let's do it now. Here is the article: "Physical Construction of Cathodes". Can you ask me some questions?
B. Certainly, I can. What types of cathodes are employed in vacuum tubes?
A. Oh! It's very simple. Two types are employed: the filamentary and the indirectly heated.
B.That's correct. Here is another question. At what potential are the different parts of the
cathode if alternating current is used for heating?
A. They are not at constant potential, on account of the IR drop of the current. B. I see that all my questions are too easy for you. And now answer my last
question: what are
the advantages the indirectly heated cathode?
A. Let me think! First of all the entire cathode is at a uniform potential and the second advantages that the heater wires are so close together that the current in them produces practically nomagnetic field.
B.From my point of view you know both English and Electronics well. If I were your English teacher I should put you an excellent mark.
6.11 Переведите используя слова
rather, indirectly heated cathode, filamentary cathode, physical construction; to have advantage over something
Эта статья довольно трудная. Мне потребовалось много имени, чтобы перевести ее. В ней говорится об устройстве катодов. Известно, что два вида катодов используются в электронных лампах. Катод с косвенным подогревом имеет два преимущества перед нитевидным катодом.
7 Lesson 7
7.1 Прочтите слова согласно транскрипции
eventually, although , oven, purpose, circuit, blood, supply , lighting , maintain , copious , cease , strontium , barium , caesium, thorium
7.2 Прочтите слова, обращая внимание на смещение ударения
definite-definition; filament-filamentary; advantage –advantageous
7.3 Сгруппируйте эквиваленты
21
minute current, stream, head phones, coil, crystal detector, filament, grid, screen, plate, addition, lighting circuit, positively charged, negative potential
наушники, сетка, анод, дополнительный, катушка, нить, положительно заряженный, небольшой ток, поток, кристаллический детектор, отрицательный потенциал, экран, осветительная сеть
7.4 Сгруппируйте синонимы
end significant, filament, if, cover, come black, finally, terminal, differ, cathode, release anode, plate , especially , important, take place, return, set free, particularly , at last, occur, coat, provided , vary
7.5 Прочтите и переведите текст
The vacuum tube
1. The most important device known to radio science is the vacuum tube. Although it is true that some receivers exist which use no tubes or valves at all, and that those which are within a very short distance of broadcasting stations and those which use only head phones can get along with coil, a condenser, and a crystal detector. The greater number of receivers use tubes, some of them one, some two, many as high as high as twelve or more.
2. As we know the tube today consists of a glass valve within which are three metallic parts known as the elements. The filament which is in the corner may be made of tungsten carbon, tungsten covered with thorium, platinum or nickel coated with oxides of barium, strontium, caesium, and other chemical elements. Next to the filament is the grid, an open mesh of molibdenum (frequently) wire screen; finally is the plate which is a sheet or screen of metal, often of nickel. Some tubes have only two elements, the filament and the plate; many have an additional grid; the mechanical construction differs according to the type of a tube, its use, and its manufacture.
3.After the various elements are placed within the tube, the glass valve is attached to a pump and the gas is removed. During the pumping process the glass valve is heated in an electric oven to drive out the gas from it, and later the elements are heated by means of an induction "furnace" so that various gases bound up in these metals may be pumped out. The modern tube is a high vacuum tube
4. Electron, which is an elementary constituent of matter carries electricity. Now electron again assumes an important role. The filament is the centre of the vacuum tube; the electrons which rush about in this filament are the life blood. When the filament is dead — due to age or crossed wires — the electrons no longer move in the proper manner the tube is dead and might as well be broken up. If a filament of tungsten is heated so that an individual electron gets up a speed of 108 centimeters per second (620 miles per second) it can break through the surfacetension of the filament. Since it is negatively charged it will be attracted toward any positive body nearby.
22
5 When the electron is released from the filament it goes shooting out into the void in which the elements are situated. When it leaves the filament, it takes with it a v' charge, and thereby leaves the filament positively charged. If there is no body at a positive potential within the bulb other than the filament, the electron will eventuallyv?ts way back to the source whence it came. If, howxever,a plate is within the tube and is more positive than the filament, the electron will be attracted to it. Even when the plate is at the proper positive potential to attract many electrons, some go back to the filament, and others congregate somewhere between the filament and the plate and constitute what is called the "space charge".
6 Every electron which hits the plate constitutes a minute electric current and when enough electrons arrive per second a measurable current is attained. It is this current by the electron from the filament which constitutes the tubes plate current which is used in so many ways. The symbol for plate current is I; the plate current is usually measured and expressed in milliamperes.
7.The source of the electrons is usually called the filament although some modern tubes get their supply of electrons in another manner. This filament is heated by a battery, called an A-battery or by a small step-down transformer from the a.-c. lighting circuit. A-battery inserted between part of the filament system and the plate maintains the plate positive with respect to the filament. It is called the B-battery.
8.When the filament is heated to a proper temperature a copious stream of electrons is emitted. Some of the electrons are attracted to the positive part of the filament, that is, to the side of the filament, a few electrons will get through the fog called the space charge but if it is at a higher potential than the filament it attracts many more electrons. It is usually so maintained by means of the B-battery and in some cases may be as high as 10 000 volts above the potential of the filament. This B-battery may be attached to the filament in several ways. Its negative end may be connected to the negative end of the A-battery or to the positive end of the A-battery. It is standard practice in the telephone plant to connect A-plus and B-minus together; in other places it is common practice to connect the two negative leads together. The most negative part of the filament in the case of d.-c. tubes, or the center of the filament in the case of tubes run from a.c., is considered as the point to which all other voltage are referred.
9.The experiment above shows that the effect of increasing the positive potential of the plate is increasing the flow of electrons. The filament temperature, too, has an important effect upon the flow of electrons. The hotter the filament, the more electrons per second will be released into the space surrounding the heated element. If, however, the voltage on the plate is low, there will soon be reached a definite plate current which cannot be exceeded no matter how hot the filament becomes. In other words the plate is taking all the electrons it can get through the space charge. It is true that more electrons leave the filament at higher temperatures but they simply add to the space charge or return to the filament. If the plate buttery voltage is increased, a greater plate current will flow. But again a point will be reached where passing more current the filament ceases to increase the plate current
7.6 Переведите словосочетания
23
according to this broadcasting station,crystal detector, glass valve, due to crossed wires , surface ,tension, space charge, minute current, a step down transformer, lighting circuit, copious stream, plate current, by means of modern receivers, the plate battery voltage, with respect to the additional grid, a step up transformer
7.7 Ответьте на вопросы
1. What is the most important device known to radio science? 2. Do all the existing receivers use tubes? 3. How many tubes do most of receivers use? 4. What does the vacuum tube consist of? 5. What material may the filament be made of? 6. What is next to the filament? 7. What happens during the pumping process? 8. What do you call the modern tube?
7.8 Переведите предложения
1. The longer rheostat wire included in the circuit, the greater the resistance. 2. The higher the value of current, the higher is the temperature of a resistor.
7.9 Прочтите диалог в ролях
Dialogue
A. Would you mind telling me, what a vacuum tube is?
ВIt is the most important device known to radio science. A. Are there any receivers which do not use tubes at all?
B. Yes, there are some, but the greater number of receivers use tubes. A. And what do receivers use instead of tubes?
B. They can get along with a coil, a condenser, and a crystal detector. A. What does a vacuum tube consist of?
ВIt consists of a glass valve within which are three metallic parts known as the elements.
A. Where is the filament?
B. It seems to me that it is in the corner of a glass valve. A. What material is it made of?
B. It may be made of tungsten, carbon, tungsten covered with thorium and other chemical elements.
A.What is next to the filament?
B.A grid is next to the filament.
AHave all the tubes three elements?
B.No, some of them have only two elements, the filament and the plate.
A.According to what does the mechanical construction of a tube differ?
B.It differs according to the type of a tube.
24