Lesson 3

Text: “The electron tubes”

Pre-text exercises:

I. Arrange synonyms in pairs:

involve, govern, amplify, vacuum tube, basic, association, main, increase, include, control, connection, valve

II. Read and translate the text: “the electron tubes”

For the last half century, electron tubes have been the dominant devices in the electronic field. Two basic phenomena are involved in electron tubes: electron emission and physical interaction between free electrons and associated circuitry. The active medium of the “material” responsible for the energy transfer is the free electron, which does not manifestate until emitted from a suitable material under the proper conditions. To move an electron in a metal from the Fermi level to “infinity”, a certain amount of work is necessary. This work, together with the kinetic energy of the electron, is given in the Richardson-Dushman equation which governs electron emission.

Electron emission has been found to be dependent upon the surface conditions of the emitter particularly as far as surfaces films and nonuniform surfaces are concerned. To achieve satisfactory emission, the emitter must be in a good vacuum. Much progress has been made in vacuum techniques in the last half century, contributing greatly to the advancement of vacuum tube technology.

From the standpoint of the physical interaction between free electrons and associated circuitry, vacuum tubes as active devices may be classified into two groups: one employs lumped-constant circuits; the other, parametric distributed lines. Conventional diodes, triodes, tetrodes and pentodes belong to the former; magnetrons and traveling waves tubes, fall into the later group.

Vacuum tubes have numerous applications in engineering, the most important being high-power high-frequency generators, and low-level signal amplifiers and detectors.

Post-text exercises:

I. Translate the following word combinations into Ukrainian:

a) electron tubes, physical interaction, energy transfer, parametric distributed lines, high-frequency generators, proper conditions, modern techniques.

b) to involve a phenomenon, to involve a problem, the problem involved, as far as radio electronics is concerned.

II. Translate the following word combinations into English:

Електронні прилади, лампа накалу, світовий промінь, поверхня приладу, електронний випромінювач, високочастотний генератор, взаємодія вільних електронів.

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

the dominant devices in the electronic field, responsible for the energy transfer, the advancement of vacuum tube technology, free electrons and associated circuitry, the kinetic energy of the electron, active devices may be classified into two groups.

IV. Put the words in order:

1. electron, and, and, electrons, emission, interaction, physical, free, associated, circuitry, between. 2. plays, an , radio, role, important, life, our, in. 3. electrons, light, causes, be, to, out, knocked, the , from, into, the, metal, ray, cathode, tube, coating. 4. penetrates, electronics, economy, the, national, of, branch, every, into.

V. Fill in the blanks with the following words:

takes place, would be increased, will be expanded, emission, makes

1. Electron … and physical interaction between free electrons and associated circuitry. 2. Electron conduction … only when the plate is positive, given pulses of current going in just this one direction. 3. Where the temperature increased, the velocity of the molecular motion … 4. Ultrasonic … use of “sound” waves above the range of human hearing. 5. The use of electronics … in all branches of science.