Vacuum tube

The introduction of vacuum __________ at the beginning of the 20th century was the starting point of the rapid growth of modern _____________. With vacuum tubes the manipulation of signals became possible, which could not be done with the early _________ and telephone circuit or with the early transmitters using high-voltage sparks to _________ radio waves.

The simplest vacuum tube, the diode, contains two ___________: the cathode, a heated filament or a small, heated, metal tube that emits electrons through thermionic emission; and the _________, or plate, which is the electron-collecting element. In diodes, the _________ emitted by the cathode are attracted to the plate only when the latter is ________ with respect to the cathode. When the plate is negatively _________, no current flows through the tube. If an alternating potential is applied to the plate, the tube passes current only during the positive halves of the cycle and thus acts as a __________.

The introduction of a third electrode, called a grid, interposed between the cathode and the anode, forms the triode, which for many years was the basic tube used for _________ current. The function of the grid is to control the current flow. At a certain negative _________, the grid, because it repels electrons, can impede the flow of electrons __________ the cathode and the anode. At lower negative potentials, the electron flow ________ on the grid potential. The grid usually consists of a network of fine _______ surrounding the cathode. The capacity of the triode to amplify depends on the small changes in the _________ between the grid and the cathode causing large changes in the number of electrons reaching the anode. Thus, the basic components of a triode _________ tube are comparable to those of the transistor which include the emitter corresponding to the heated ________ of the triode tube as the source of electrons.

Grid Anode

Cathode Anode

Grid

Heated Cathode

Appearance Electrodes (the glass tube Circuit symbol

Is broken)

Fig. 28. Vacuum triode.

Vacuum tubes have now been almost entirely replaced by transistors, which are cheaper, smaller, and more _________. Tubes still play an important role in certain applications, however, such as in power stages in radio and television transmitters, and in scientific and military __________ that must resist strong voltage pulses which destroy transistors. The cathode ray ________ is still a base of some kind of displays, e.g. in radar equipment.

Exercise 2. Answer the following questions.

1. What is the diode used for?

2. What is the function of the additional electrode, the grid, in the vacuum triode?

3. Which devices of mentioned above are used for rectification of a direct current into alternating one?

4. What kinds of rectifying circuits with transistors or vacuum tubs do you know?

5. Do vacuum tubes have any advantages over transistors?

6. Are transistors more reliable than vacuum tubes?

7. What adjectives can be used with the noun “tube”?

Exercise 3. Decide whether the following statements are true or false in relation to the information in the text in the Exercise 1. If you think the statement is false, change to make it true.

1. Any vacuum tube has at least three electrodes.

2. The electric current in the vacuum tube is a flow of positively charged ions.

3. The greed in a vacuum tube needs to be heated.

4. In certain condition the greed and the plate can emit electrons by themselves.

5. The intercity of electron stream in the vacuum tube always depend on voltage between the cathode and plate.

6. Transistors usually consume more power than vacuum tubes.

7. Nowadays most of people have never seen any vacuum tube.

Граматичні відомості

Місце прийменника у реченні. Збіг за формою деяких прийменників та прислівників

Зазвичай, як і в українській мові, прийменник в англійському реченні стоїть перед іменником чи займенником:

Ann studies at the university.

You must talk to him.

Якщо перед іменником є означення, то прийменник ставиться перед цим означенням:

I live in a big house.

Однак у деяких випадках, особливо це характерно для усного мовлення, прийменник також може відокремлюватись від іменника або займенника та розташовуватись у кінці речення:

Whom do you speak to? (To whom do you speak?)

The place which he is going to (to which he is going) seems very distant.

Таке відокремлення прийменника від об’єкта також характерно для деяких пасивних та інфінітивних зворотів, що були розглянуті раніше:

The priest was sent for. В активному стані: They sent for the priest.

I have no tools to work with.

Слід зауважити, що ті самі слова у різних ситуаціях можуть виконувати роль як прийменника, так і прислівника:

Tim had climbed up a tree to get a better view. – Тім зібрався на дерево, щоб побачити кращій краєвид. – Прийменник.

Tim climbed up to see better. – Тім забрався вгору, щоб краще бачити. – Прислівник.

Часто такі слова нерозривно пов’язані з дієсловами, утворюючи так звані подвійні (інколи потрійні) дієслова (two/three-word verbs): to turn on (off) – вмикати (вимикати), to put on (off) – одягати (знімати), to cross out – закреслювати, to drop out of – припиняти щось відвідувати). Як правило, слова on, off, out і т. ін. виконують роль прислівника, оскільки характеризують процес, дієслово, а не просто виконують роль зв’язки між дієсловом та іменником.

Остання частина подібного подвійного дієслова може відокремлюватись і переноситись на кінець речення:

Please turn off the light. = Please turn the light off. – Будь ласка, вимкніть світло.

Оскільки на практиці питання про приналежність слів до певної частини мови не дуже важливе для більшості людей, у словниках і фразеологічних посібниках вищезгадані прийменники-прислівники розглядаються разом. Таким чином це зроблено й у додатку 2 цього посібника, де поруч з прийменниками надані приклади і для прислівників, що збігаються за формою з прийменниками.

Exercise 1. Translate the sentences into English.

1. Над ким він сміявся?

2. Кого вона шукає?

3. Запитайте його, від кого він щойно отримав повідомлення.

4. Проблема, над якою вони зараз працюють, дуже актуальна.

5. У мене нема олівця, щоб я міг писати.

6. Він вчиться в університеті, добре відомому в усьому світі.

Exercise 2. Listen to an introduction of a teacher at a beginning of a class. Find out in the text two word verbs. Pay attention that in all cases the object is between the verb and preposition. Then try to read the text in another way, putting the object after the preposition. After reading check yourself listening to the text again.

Good morning for everybody. Today I’m going to explain you how to use a new program. First of all I want you to take your pens and notebooks off and be ready to write all I say down. Nick, please pull the windows shades down: today the sun shines too brightly. And Ann, please pick all these things up. Maybe the previous group left them. Peter, try the computer out. Don’t forget to turn the main switch on. Ann, turn your mobile phone off. Now, let’s start. Peter, put the CD in and run the program.

Комунікативна практика

Порівняння об’єктів

First listen to the following conversation as an example and then practice your own conversation with you partner. Use adjectives and adverbs including comparative and superlative forms as often as you can.

A: What city do you like, Ann?

B: Kyiv is the best.

A: Why?

B: It's exciting. It's bigger. The buildings are taller. The people are livelier.

A: I understand what do you mean, but I like Poltava better.

B: Why is that?

A: Well, it’s slower, it’s smaller, and it’s cosier.

B: OK. You know as they say, “The east, the west, the home is best”.

Exercise. Practice conversation with you partner following example. Use adjectives and adverbs including comparative and superlative forms.

Вправи для самостійної роботи

Exercise 1. Translate the text from pages 195-196 into Ukrainian (Russian).

Exercise 2. Find out in the text words with opposite meaning.

cathode accelerate cooled absorb positively constant bigger weak negligible partly attract

Exercise 3. Fill in the spaces with appropriate prepositions if need be.

1. In 1720 Euler entered ... the University of Basel.

2. Euler took D. Bernoulli's place ... the head ... the department ... mathematics.

3. ... that period he wrote his famous book ... mechanics.

4. The book had a great influence ... subsequent developments ... mechanics.

5. He devoted all his time ... mathematical research.

6. He was approaching ... complete blindness.

7. This enabled ... the assistants to continue the research.

8. They put the results ... writing ... Euler's approval.

Lesson 6

ВИВЧЕННЯ ТЕРМІНОЛОГІЇ ЗА ТЕМОЮ МОДУЛЯ

Exercise 1. Answer the following questions.

1. What gives the transistor an advantage over the vacuum tube?

2. What does simple transistor consist of?

3. How is it possible to regulate semiconductors’ conductivity?

4. Which additives can be used to stimulate conductivity of n- and p-types in different semiconductors?

5. Do you know something about rectifiers on semiconductors? How do they work?

6. Which common household appliances and instruments use transistors and integrated circuits?

7. Why is low consumption of energy important for modern electronic equipment and devices?

Exercise 2. Insert the words the best suited to the sentences using the list below. Each of words in the list is used only once. Then listen and check your guesses.

Semiconductor materials may be divided into two _________ groups: intrinsic and extrinsic. An intrinsic semiconductor is chemically very pure, and its __________ is poor. Some common intrinsic semiconductors are single ________ of silicon, germanium, and gallium arsenide. These may be converted into the more useful extrinsic _____________ by the addition of small amounts of impurities. This process, known as doping, alters the ___________ properties of the semiconductor and _______ its conductivity.

For example, the atom of an intrinsic semiconductor such as _________ silicon has four electrons in its outermost shell. These electrons attach the ________ atom to its neighboring atoms and so are not free to move through the solid. Accordingly, since electric ________ relies on charge motion, pure silicon is a poor _________ of electricity. If arsenic atoms, with five outer electrons, are _________ for some of the silicon atoms, the fifth electron is not needed for binding to adjacent atoms and is free to move through the solid. Thus, ________ silicon with arsenic improves the silicon’s conductivity. On the other hand, if a silicon atom is _______ by an indium atom, which has three valence________, an electron is missing from one covalent bond, _______ an empty space, so-called hole. This hole can move about, just as the free electron could. A region with such indium ___________ is called p-type silicon because the holes act like carriers of positive charges, and thus they also serve to _________ the silicon’s conductivity. An extrinsic semiconductor is commonly _________ as n- or p-type, depending on whether the impurity added has an excess of negative charge (n-type) or a deficiency of negative _________ (p-type).

In the p-n-p type transistor, the first part, ___________ the emitter, is doped to give it an excess of positive charges; the second, the base, is doped to give it _______ negative charges; and the third, the collector, is doped like the first part to give it an excess of _________ charges.

substituted general classified leaving positive crystals conductivity excess electrical improves elemental silicon current conductor doping replaced electrons increase charge semiconductors called impurities

binding covalent extrinsic semiconductor intrinsic semiconductor

зв’язування (хімічне) ковалентний напівпровідник із домішковою провідністю напівпровідник із власною провідністю