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EXERCISES. 1. What does a diode characteristic show?

I. Review questions:

1. What does a diode characteristic show? 2. What is kept constant while the tube characteristic is being obtained? 3. What controls the plate current in the low plate-volt-region? 4. What is independent of the cathode tempera-ture? 5. Under what conditions is the plate current said to be space-charge limited? 6. When does the emission satura-tion take place? 7. Why are the diode tubes used as rectifiers? What current do they rectify?

II. Make up an abstract of the text basing on the answers
to the above questions.

III. Translate the international words without a dictionary:
anode, diode, effect, characteristic, constant, total

IV. Define the meanings of the prefixes in the. following
words and translate the words:

abnormal, misdirection, unheated, interchange, overload, irregular, reconvert, dissimilar, non-effective, impossible, illegal, independence, co-operate, subdivide, semicircle, su­pernatural, self-determination, post-war, pre-war, underlie, foregoing, neo-realism

V. Translate these antonyms and memorize them:

1. best (adj), worst

2. constant (adj), variable

3. never (adv), always

4. increase (v), decrease

5. obtain (v), lose

6. take (v), give

7. different (adj), similar

8. normally (adv), abnormally

9. partial (adj), total
10. many (adj), few

VI. Translate these verbs and learn them:

to take place, to become, to determine, to depend on (upon), to reach, to represent, to overcome, to establish, to follow, to fill

Test 1

Find the correct answer out of the three given to each question:

1. Which of the following tubes consists of a cathode and a
plate:

a triode tube, a diode tube, a tetrode tube

2. Which of the following charges repel each other:

like charges, unlike charges, positive and negative charges

3. Which of the following charges are emitted from the
cathode of an electron tube:

unlike charges, positive charges, negative charges

4. Which of the following charges in respect to the cathode
must have an anode to transmit the direct current:
positive charges, negative charges, neutral charges

5. Which of the following is established within the tube by
applying a potential difference:

an electric field, ionization, de-ionization

Test 2

I. Find Russian equivalents for the English words and word combinations (see p. 147):

1. as well as (а) или... или

2. both (b) относительно, в отношении

3. whether... or (с) в конце концов

4. with respect to (d) оба

5. therefore (e) друг друга

6. as long as (f) вообще, обычно

7. eventually (g) соответственно

8. each other (h) а также и

9. correspondigly (i) поэтому

10. generally (j) пока

II. Find Russian equivalents for the English verbs (see p. 32):

1. reach (а) происходить

2. follow (b) становиться

3. take place (с) устанавливать

4. become (d) достигать

5. fill (е) следовать

6. establish (f) преодолевать

7. overcome (g) представлять, изображать

8 depend on (upon) (h) определять

9 represent (i) наполнять(ся)

10 determine (j) зависеть от

Test 3

Find an antonym (a), (b), (c) or (d) to the word in bold type;

I To attract electrons — (a) produce; (b) conduct; (c) repel, (d) lose

2. To stop the plate current — (a) measure; (b) transfer; (c) convert; (d) start

3. Closed circuits — (a) open; (b) internal; (c) external;

different

4. A constant value — (a) high; (b) variable; (c) low; (d) abnormal

5. A simple structure — (a) heavy; (b) light; (с) compli-ld; (d) modern

6. To increase the stream of electrons — (a) obtain;

decrease; (c) change; (d) stop

7. The best method — (a) unknown; (b) main; (c) worst; (d) principal

8. The electrons are strongly repelled — (a) weakly;

never; (c) always; (d) quickly

9 To be connected externally—(a) indirectly; (b) di-lу; (с) strongly; (d) internally

v

10. This value never decreases — (a) sometimes; (b) nor­
mally; (с) always; (d) often

11. Similar problems — (a) well-known; (b) different;

(c) important; (d) quite understandable

12. To lose strength — (a) depend on; (b) limit; (c) gain;

(d) determine

13. A correct answer — (a) wrong; (b) good; (c) bad;
(d) clever

14. The process is continued—(a) started; (b) changed;
(c) interrupted; (d) finished

15. The same conductors — (a) different; (b) bad;

(c) good; (d) similar

16. When it remains—(a) starts; (b) gives; (9) leaves;

(d) works

17. To give an idea — (a) discuss; (b) simplify; (c) take;
(d) understand

18. The total supply of electrons — (a) steady; (b) par­
tial; (c) constant; (d) continuous

19. It can be obtained—(a) made; (b) measured;
(c) controlled; (d) lost

20. It is normal that — (a) said; (b) known; (c) abnormal;
d) found

Test 4

Finish each sentence choosing one of the three variants (a). (b) or (c) based on the texts from Section III:

1. The diode is...

(a) the simplest combination of elements constituting an electron tube; (b) the most complicated combination of elements constituting an electron tube; (c) a tube with three electrodes.

2. A diode consists of...

(a) an anode alone; (b) a cathode alone; (c) a cathode and a plate.

3. The cathode serves as...

(a) a collector of electrons; (b) a source of electrons; (c) a source of positive particles.

4. The anode serves as...

(a) a source of electrons; (6) a collector of electrons; (c) a source of uncharged particles.

5. A basic law of electricity states that...

(a) like charges repel each other; (b) like charges at­tract each other; (c) unlike charges repel each other.

6. Electrons emitted from the cathode of an electron tube are... (a) positive electric charges; (b) positively charged particles; (c) negative electric charges.

7. An electric field is established by applying to the electro­
des...

(a) heating energy; (b) a potential difference; (c) light energy.

8. Electron current flows in the diode only when...

(a) the plate is made negative; (b) the plate is made positive; (c) the plate has no charges.

9. Electron current flows in the diode only when...

(a) the cathode is made positive; (b) the cathode has no charges; (c) the cathode is made negative.

10.. At a given operating temperature the total number of
electrons emitted by the cathode of a diode is always...

(a) different; (b) the same; (c) increasing.

11. The cloud of electrons formed in the space between the
cathode and the plate is called...

(a) a space charge; (b) an interelectrode space; (с) а positive external charge.

l2. The space charge is...

(a) negative; (b) positive; (c) neutral. 13. The space charge has...

(a) an attracting effect on electrons; (b) no effect at all; (c) a repelling effect on electrons.

14. The flow of electrons to plate is an electric current cal­led...

(a) an alternating current; (b) an internal current; (c) a plate current.

15. The amount of plate current depends on...

(a) the interelectrode space; (b) the space charge; (c) the negative plate voltage.

16. The plate current is space-charge limited when...

(a) at low plate voltage the negative space charge lim­its the flow of electrons; (b) the plate current reaches saturation at high plate voltage; (c) the negative space charge has an attracting effect on electrons.

17. The plate current is said to be emission-limited in the high plate-voltage region when...

(a) the plate current has variable value, (b) the emit­ted electrons are repelled from the plate; (c) the emission saturation takes place.

18. In general, electron tubes are operated in...

(a) the high plate-voltage region; (b) the space-charge limited region; (c) the saturation region. 19. The principal advantage of the diode tube is that it per­mits the flow of current in...

(a) one direction only; (b) two directions; (c) no direc­tion. 20. The diode tubes are often used as...

(a) stabilizers; (b) amplifiers; (c) rectifiers.

(See keys to the tests on p. 147.)

Translate into Russian without a dictionary:

TEXT

1. A diode is a two-element electron tube that consists
of a cathode and an anode or plate acting as an electron col­
lector. By applying a positive voltage to the plate of a diode,
an electric field is established between cathode and plate
that attracts electrons emitted from the cathode to the plate.

2. Plate current is the flow of electrons from cathode to
the plate and their return to the cathode through the external
circuit. Plate current flows in a diode when the plate is made
positive with respect to the cathode. No current flows when
the plate is negative with respect to the cathode. This is
called unidirectional conduction.

3. The cloud of electrons formed in the space between ca­
thode and the plate is called space charge. The space charge
is negative and hence has a repelling effect on electrons emit­
ted from the cathode. The amount of the plate current de­
pends on the space charge and the relative strength of the
electric field set up (создаваемого) by the positive plate
voltage.

4. At low plate voltages the negative space charge limits
the flow of electrons and the plate current is completely con­
trolled by the plate voltage and is independent of cathode
temperature. The plate current is space-charge limited. At
high plate voltages the space charge is drawn off (исчезает)
and the plate current reaches saturation at a value equal to
the total emission current. It is then independent of the
plate voltage and is said to be emission-limited for a specific
cathode temperature. As the diode tube permits the flow of

current in one direction only it is often used as a rectifier to change alternating current to direct current.

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