Present Continuous

Affirmative

am/is/are + -ing

For example:

· I am plugging this device in today.

· Look! Current is flowing through the tube.

· They are placing the grid between the cathode and the plate at the moment.

Spelling

Verbs that end in –e (make) – ing: make-making

Verbs that end in –ie (lie) – ing: lie-lying

Negative

For example:

· I am not working as a physicist now.

· These devices are not heating this week.

· Look! They are not placing the grid between the cathode and the plate.

Questions

For example:

· Why aren’t these devices heating this week?

· Look! They are placing the grid between the cathode and the plate at the moment, aren’t they?

Adjectives and adverbs

1) Adjective + noun

For example:

· a modern amplifier

· a good conductor

· a precise definition

But: Look/feel/smell/taste/sound/get + adjective

2) Verb + adverb

Adjective + -ly = adverb

For example:

· to control well

· to conduct readily

· to operate quickly

3) Degrees of Comparison

But: good – better – the best

bad – worse – the worst

little – less – the least

much/many – more – the most

1. Fill in the table.

2. Read and translate the following international words:

Nouns (n): effect, function, idea, ion, material, metal, milliampere, reflector, result, secret, spiral, triode, volt

Verbs (v): compensate, control

Adjectives (adj): modern, miniature, standard

3. Write the following verbs with –ing. Mind the spelling.

Control, decrease, depend, increase, place, result, conduct, insulate, heat, emit, flow, have, apply, use.

4. Look at Fig.1 and complete the sentences with the following verbs in the correct form: attract, repel, heat, flow, emit.

Fig.1. Electron flow in a vacuum tube

1. The heater … the cathode.

2. The cathode … electrons.

3. Negative voltage on the cathode … the electrons.

4. Positive voltage on the plate … the electrons.

5. Current … from one element to the other through a gas.

5. Make up questions from these words. Use is or are and put the words in order.

1. the\in\student\the\electron\describing\a\vacuum\flow\tube.

2. the\electronics\defining\physicist.

3. the\emitting\cathode\electrons.

4. the\the\electrons\cathode\flowing\from\to\the\plate.

5. the\between\grid\being placed\the\cathode\and\the\plate.

6. the\grid\the\flow\of\electrons\controlling.

7. current\from\moving\element\to\one\the\other\a\gas\through.

8. a\small\negative\voltage\being applied\to\the\grid.

9. the\decreasing\plate\current.

10. being used\for\amplification\a\triode.

11. flowing\only\current\in\direction\one.

6. Put the verb in brackets into the correct form, Present Continuous or Present Simple.

1. This scientist (to be) never satisfied. He always (to complain).

2. In a vacuum-tube triode there (to be) three electrodes: a cathode, a plate and a grid.

3. When heated the cathode (to emit) electrons.

4. I see in Fig.1 that the electrons (to flow) from the cathode to the plate.

5. The grid (to control) the flow of electrons when the device is switched on.

6. The closer the grid (to be) to the cathode, the more influence it has on the electron flow.

7. Look! The plate current (to decrease).

8. We are decreasing the negative voltage on the grid to 8 volts, and the current gradually (to increase).

9. Due to this property of a triode, it (can) be usedfor amplification.

10. Usually he (to work) as a software maker, but he (to read) lectures now.

11. The number of electrons (to increase) very rapidly in this device.

12. It (to get) late. Let’s finish the experiment.

13. The grid (to be) placed between the cathode and the plate.

14. A: You (to work) hard today. B: Yes, I have a lot to do.

15. Even if a small negative voltage is applied to the grid, this (to result) in a large plate current.

Formulate the rules.

7. Form nouns from the following verbs using the suffix -or, -еr and translate them:

For example:

amplify — усиливать; amplifier — усилитель

conduct — проводить (ток);

control — управлять;

detect — обнаруживать, определять;

divide — делить;

learn — учить;

operate — приводить в действие;

heat — нагревать;

insulate — изолировать;

emit — испускать;

direct — направлять;

use — использовать;

rectify — выпрямлять (ток).

8. Choose the appropriate English equivalents:

ближе— 1. close; 2. closer; 3.the closest

лучше— 1. good; 2. better; 3. the best

больше— 1. the most; 2. more; 3. much

самый маленький— 1.small; 2. smaller; 3. the smallest

самый большой— 1. the largest; 2. large; 3. larger

выше—1. high; 2. higher; 3. the highest

Remember the spelling: big – bigger

9. Translate the following sentences. Mind the meaning of the highlighted words.

1. The farther the grid is from the cathode, the more the plate current is. 2. The wider the distance between the grid wires, the more the plate current is. 3. The higher the temperature, the lower the conductivity of a metallic conductor. 4. The lower the temperature, the better the conductivity of a metallic conductor. 5. The slower the electrons move, the easier it is to stop them and return them to the space charge. 6. The closer the grid is to the cathode, the more control it will have on electron flow to the plate. 7. The more heavily the material is doped, the lower its electrical resistance will be. 8. The hotter the cathode becomes, the more electrons it emits per unit time (в единицу времени). 9. As the electrons move out into space, they form a cloud (облако) of negative charges. The larger this cloud becomes, the more opposition it offers to additional electrons leaving the cathode. 10. The more negative the grid, the less the plate current will be. 11. The greater the load resistance of a tube amplifier, the greater is the voltage amplification.

10. Translate

A. start from the first component

anode current, electron tube, large plate current, semicoductor device, small negative voltage, large negative voltage, gas-filled envelope

B. start from the second component

electron flow, current flow, potential increase

11. Translate the following sentences. Start your translation from an adverbial modifier of place.

1. There is one grid in a triode. 2. There are two grids in a tetrode. 3. There are three grids in a pentode. 4. There is no grid in a diode.

12. Match the following sentences with their translations.

13. Choose as many words from the table оf ex. 1 as you can and form sensible sentences in Present Continuous (affirmative, negative and interrogative).

For example: In Fig. A the grid is controlling the current flow.

SPECIALIST READING

14. Read the text “Triodes” and choose its best summary.

1. The electron flow in a triode.

2. The influence of the grid on the electron flow.

3. The structure of a triode, basic principles of its operation and functions.

In a vacuum-tube triode there are three electrodes: a cathode, a plate and a grid. When heated the cathode emits electrons. Electrons flow from the cathode to the plate. The grid is placed between the cathode and the plate. It controls the flow of electrons. The closer the grid is to the cathode, the more influence it has on the electron flow. Even if a small negative voltage is applied to the grid, this results in a large plate current. If a large negative voltage is applied to the grid, the plate current decreases. For example, the plate voltage is 150 volts. A small negative voltage of 10 volts is applied to the grid. This results in a current flow of 20 m. a. But if the negative voltage on the grid is decreased to 8 volts, this will result in a current of 30 m.a. Due to this property of a triode, it can be used for amplification.

15. Read the text again and complete the sentences.

1. In a vacuum-tube triode there are…

2. When heated…

3. Electrons flow…

4. The grid is placed…

5. … the flow of electrons.

6. The closer the grid is to the cathode …

7. … this results in a large plate current.

8. If a large negative voltage is applied to the grid …

9. … it can be used for amplification.

Match the terms in Table A with their definitions in Table B

SPEAKING

16. Work in pairs. Draw a circuit of a triode and ask your partner some questions based on it. Make sure all the questions and answers are in Present Continuous.

For example:

Student A – In what direction are the electrons shown in the scheme moving?

Student B – They are moving towards the plate.

17. Summarize the text “Triodes” in 150 words using the following plan:

1. The structure of a vacuum-tube triode.

2. The principles of its work.

3. The function of a grid.

4. The influence of the distance between the cathode and the grid on the electron flow.

5. The influence of the voltage on the current flow.

6. The grid application.

18. Compare a vacuum-tube triode with a diode using appropriate degrees of comparison and the following words of comparison and contrast: both, like, whereas, unlike, but, however.

For example: 1. When heated in both tubes cathodes emit electrons.

2. A triode can be used for amplification unlike a diode which is used as …

19. Act as an interpreter. Translate the description of the operation of a semiconductor triode given by your group mates from Russian into English.

20. Divide into 2 groups. Group 1 translates Extract A and group 2 – extract B of the text “Heat Transfer and Appearance of Tubes” with a dictionary in writing.

Highlighted words are international. Try to guess their meaning without a dictionary.

Extract A

Any types of vacuum tubes can be recognized from their appearance. A considerable amount of heat is produced when tubes operate. In most circuits the tube is about 30-60% efficient depending on the class of operation (classes A, B, or C), which means that 40-70 % of input power is lost as heat. The requirements for heat removal significantly change the appearance of high-power vacuum tubes.

Most tubes contain two sources of heat when operating. The first one is the filament or heater. Some types contain a directly heated cathode. This is a filament similar to an incandescent electric lamp and some types glow brightly like a lamp, but most glow dimly. (The "bright emitter" type possesses a tungsten filament alloyed with 1-3 % thorium which reduces the work function of the metal, giving it the ability to emit sufficient number of electrons at about 2000 degrees Celsius. The "dull emitter" types also possess a tungsten filament but it is coated by a mixture of calcium, strontium and barium oxides, which emit electrons easily at much lower temperatures due to a monolayer of mixed alkali earth metals coating the tungsten when the cathode is heated to about 800-1000 degrees Celsius.)

The second form of cathode is the indirectly heated form which usually consists of a nickel tube, coated on the outside with the same strontium, calcium, barium oxide mix used in the "dull emitter" directly heated types, and fitted with a tungsten filament inside the tube to heat it. This tungsten filament is usually uncoiled and coated by a layer of alumina, (aluminium oxide), to insulate it from the nickel tube of the actual cathode. This form of construction allows for a much greater electron emitting area and, because the heater is insulated from the cathode, the cathode can be positioned in a circuit at up to 150 volts more positive than the heater or 50 volts more negative than the heater for most common types. It also allows all the heaters to be simply wired in series or paralleled rather than some requiring special isolated power supplies such as specially insulated windings on power transformers or separate batteries.

Extract B

For small-signal tubes such as used in radio receivers, heaters are rated from 50 mW to 5 watts, (directly heated), and about 500 mW to 8 watts for indirectly heated types. Once filament/heater power is included in total power consumption, small tubes have very poor efficiencies. A 6BM8/ECL82 audio stage consumes a total power of some 15 watts for 3.5 watts of useful audio power, giving an efficiency of around 23%. Some signal amplifiers, particularly high-frequency amplifiers such as the 6BA6, consume some 5.9 watts of power in normal operation and deliver only 1.1 watts of power at the plate.

The second source of heat is generated at the anode, when electrons, accelerated by the voltage applied to the anode, strike the anode and impart a considerable fraction of their energy to it, raising its temperature. In tubes used in power amplifying or transmitting circuits, this source of heat will exceed the power dissipated in the cathode heater. (The plates or anodes of 6L6 devices used in guitar amplifiers can sometimes be seen to reach red heat if the bias is set too high, they should not emit any visible radiation when driven at maximum ratings.) No tubes in domestic, music, or studio equipment should operate with glowing anodes.

This heat usually escapes the device by (black body) radiation from the anode/plate as infra red light. Some is conducted away through the connecting wires going to the base but none is convected in most types of tube because of the vacuum and the absence of any gas inside the bulb to convect.

For devices required to radiate more than 500 mW or so, usually indirectly heated cathode types, the anode or plate is often treated to make its surface less shiny, (see black body radiator), and to make it darker, either gray or black. This helps it radiate the generated heat and maintain the anode or plate at a temperature significantly lower than the cathode, a requirement for proper operation.

Other internal elements of high-power tubes, such as control grids and screen grids, may also dissipate heat if carrying large currents. Limits to grid dissipation are listed for such devices to prevent distortion and failure of the grids.

21. In Russian write a content-based summary of the text you have translated.

22. Translate into English the summary made in ex.21 of the text you haven’t read.

23. Make a reverse written translation (from Russian into English) of the Extract you have translated.

24. Serve as simultaneous interpreter. Make an oral reverse interpretation of the text.

25. Find more information about vacuum tubes and tell your group mates.

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