Lesson 1

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Lesson 1

Require, present-day, function, apply, demand, hence, usually, use, modern, operate, commonly, principally, mainly, consequently.

Tiny, heat, light, raise, heavy, to increase, cool, giant, reduce, confined, inside, to come out of, outside, input, to come into, slowly, to decrease, output, complicated, rapidly, simple.

Of all the component parts used in modern systems radio communication, the electron tube is the most important one. Many of the basic principles of radio were well understood for years before, they could be applied in practice, put their development and practical use had to await the discovery and improvement of the vacuum tube.

Vacuum tubes are made in all sizes from the tiny tube to the giant 100 kW water-cooled tube used in larger radio transmitters. They function as oscillators, amplifiers, detectors, rectifiers, modulators, as voltmeters, oscillograph an in any special ways. The importance of having as a good working knowledge of their properties and applications cannot be overestimated.

Metallic conductors are composed of atoms and molecules, with a great number of free electrons in continue random motion, which are not bound closely to particular atoms. If the temperature of a conductor is raised sufficiently, some of these free electrons will acquire enough kinetic energy to permit their escape by penetrating the surface of the conductor. This process is known as thermionic emission and it is found that various metals differ widely will respect to this property. In present-day tubes, the most commonly used materials for the purpose are as following tungsten, thoriated tungsten, oxide-coated emitters.

Emitters made of tungsten are used principally in large transmitting tubes, where heavy emission current, are required. Tungsten emitters must be operated at 2.500° (degrees Kelvin = degrees Centigrade +273°), and they require relatively large amounts of power for heating. The operating temperature is close to the melting point of tungsten, and consequently the heating voltage must be regulated. Within this limitation, however, tungsten emitters are rugged and long-lived, and capable of withstanding considerable overloads.

Thoriated tungsten is tungsten containing a small percentage of thorium oxide. After suitable heat treatment it is found that migration of thorium atoms produces activated layer on the filament surface, with the result the electrons are emitted at a much lower temperature (1.900°K) than for pure tungsten. This type of cathode has, therefore a great emission efficiency, but it is much more sensitive to overload than pure tungsten, as the thorium layer is stripped off or evaporated when excessive emission current and demanded.

Filaments and indirectly heated cathodes of oxide-coated type consist of an inert base, usually a nickel alloy covered with a layer of barium and strontium oxides. Cathodes of this type operate at a still lower temperature (1500°K), and the emission efficiency is very high. Almost of tubes of the small receiving type, as well as many medium size utilize cathodes of this type.

a) larger radio transmitter, filament surface, present-day tubes, thorium layer, heat treatment, emission current.

b) to apply in practice, a great number of free electrons, with respect to this property, within this limitation, as well as.

Сучасні системи радіокомунікації, ступінь випромінювання дуже високий, найбільш чутливий до перенавантажень, нитка розжарювання, покращення вакуумних ламп.

III. Give the Ukrainian equivalents for the following English word combinations:

large transmitting tubes, the discovery and improvement of the vacuum tube, large amounts of power for heating, considerable overloads, the temperature is raised sufficiently, various metals differ, produces activated layer.

1. indirectly, of, an, filaments, type, cathodes, and, heated of, oxide-coated, consist, inert, base. 2. in, tubes, are made, vacuum, sizes, all. 3. at, tungsten, Kelvin, must be, emitters, operated, 2.500° degrees. 4. is, containing, small, oxide, thoriated, tungsten, tungsten, a, percentage, of, thorium.

1. Filaments and indirectly heated cathodes of oxide-coated type …of an inert base. 2. Vacuum tubes …in all sizes. 3. Tungsten emitters … and long-lived, and capable of withstanding considerable overloads. 4. Many of the basic principles of radio … well understood for years before. 5. This type of cathode … great emission efficiency. 6. Some of free electrons … enough kinetic energy. 7. The electrons of their atoms … free to move.

1. Filaments and indirectly heated cathodes of oxide-coated type consist of ….2. Vacuum tubes are made in all sizes from … 3. Many of the basic principles of radio were well understood for….4. Metallic conductors are composed of …5. If the temperature of a conductor is raised sufficiently, some of free electrons …6. The operating temperature is close to the melting point of …7. Emitters made of tungsten are used principally in large … 8. Almost of tubes of the small receiving type, as well as many…

VII. Which of the following statements are true or false? If the statement is wrong, correct it:

1. Of all the component parts used in modern systems radio communication, the electron tube is the most important one. 2. Tungsten emitters must be operated at 273° (degrees Kelvin = degrees Centigrade +2.500°). 3. This type of cathode has, therefore small emission efficiency. 4. Vacuum tubes are made only one size. 5. Metallic conductors are composed of atoms and electrons.

1. What is the most important of all the components in modern systems of radio communication? 2. In what sizes are vacuum tubes made? 3. What are metallic conductors composed of? 4. What process is known as thermionic emission? 5. Where are emitters made of tungsten used? 6. At what temperature must tungsten emitters be operated? 7. What is thoriated tungsten? 8. When does migration of thorium atoms produce are activated layer on the filament surface? 9. What do filaments and indirectly heated cathodes consist of?

1. Many of the basic principles of radio were well understood for years before. 2. Thoriated tungsten is tungsten containing a small percentage of thorium oxide. 3. Tungsten emitters require relatively large amounts of power for heating. 4. The operating temperature is close to the melting point of tungsten. 5. Construction an electron microscope became possible after numerous experiments. 6. An electric conductor being moved in a magnetic field, an electric current is generated.

1. He likes reading English scientific books. 2. They think of applying electronic devices in their laboratory. 3. This little girl likes being read to. 4. Flying into outer space has been man’s age old dream. 5. Our government takes great care of the development of science b providing our scientist with all necessary things for their research work. 6. Before carrying out this experiment he carefully examined all the instruments. 7. Many Institutes have been established for training specialists for various branches of our national economy. 8. The idea of building artificial satellites belongs to K.Tsiolkovsky. 9. After producing the electronic equipment we raised the efficiency of some processes. 10. In our country great progress has been achieved in developing all branches of science and engineering. 11. Soviet scientists having made the great contribution to the cause of conquering cosmic space as well known in the whole world. 12. We where told about their having studied a number of problems connected with the development of radio electronics. 13. Their wish is mastering the fundamentals of radio engineering. 14. Scientists could not improve without making numerous investigations in this branch of radio engineering. 15. Look at the readings of the meter.16. The thorough mastering of English is extremely necessary for engineers.

XI. Translate the following sentences paying attention to the functions of the Gerund:

1. Encoding is the function of the transmitter. 2. Visual and audible signals are used for conveying information. 3. Коtelnikoy and Wierner's having recognized clearly the fundamental role of noise in limiting the performance of communication systems had an important influence in modulation theory. 4. Our having mastered a foreign language help us in our work. 5. We suggested the plan being discussed at the conference. 6. He prevented the letter from being sent of.

1. Він наполягав на проведенні експерименту. 2. Вимірювання температури потрібно для проведення багатьох експериментів. 3. Вчені почали працювати над конструюванням напівпровідників у кінці 19 сторіччя. 4. Ми цікавимось дослідженням в області електорніки. 5. Вивчення властивостей електронів вплинуло на створення мікроскопів.