2.2.4 Define synonyms

failure n, purpose n, helix n, furnish v, investigation n, obtain v, apparent a, nearly adv, resemble v, chiefly adv, almost adv, mainly adv, principally adv, evident a, get v, receive v, research n, spiral n, supply v, fault n, aim n

2.2.5 Find and translate sentences with Participle I in the function of attribute (paragraph 1); with the verb in the meaning of obligation (paragraph 2); adjective in the comparative degree, give another two degrees of this adjective

CHARACTERISTIC CURVES OF TRIODES

1. The effect of grid and plate potentials on flow of plate current can be investigated by means of the circuit of Figure3. In this set up, if the plate potential E_b is held constant and the grid potential varied, one of the curves of Figure 4 is obtained. The other curves are found in the same way, by using different values of Eh. Such a set of curves, showing the relationship between the plate current and the grid potential for constant values of plate voltage, is known as the family of mutual characteristics of the tube. By use of this family, interpolating between curves where necessary, it is possible to find the plate current corresponding to any combination of grid and plate potentials.

2. The effect of temperature saturation is not apparent. The reason for the absence of saturation is that in most modern tubes the cathode is capable of furnishing many more electrons than are required for rated current. As a result, a certain amount of variation in filament or heater voltage can be tolerated without seriously impairing the tube performance, and the useful cathode life is increased. It will also be noted that the curves tend to be nearly straight lines in the upper portions, and that the curves for various plate potentials are nearly parallel. It will be shown later these properties are important where the tube is to be used as an amplifier, and where it is desirable to keep the distortion of the amplified signal as small as possible.

3. 

   Figure 3-Circuit for Obtain­ing Triode Characteristics

   Figure 4-Mutual Charac­teristics of 6Z5 Triode

   Another way of presenting the same information is shown in Figure 5. Here the grid potential is held constant for each curve, and the plate potential is permitted to vary. This set of curves is known as the family of plate characteristics, and for many purposes it is more useful than the mutual characteristics. The effect of increasing the negative grid potential is chiefly to shift the curves toward the right on the diagram, without causing much change in form.

A

Z

A

r

0 SO 160 241) 320 400 400

Figure 5-Plate Characteristics of 6Z5 Triode

2.2.6 Translate the word-combinations

1. tube performance; the family of mutual characteristics of the tube.

2. the curves tend to be nearly straight lines; by means of; by use of; in the same way; as a result; the same information, some information.

7. Answer the questions

1. What is known as the family of mutual characteristics of the tube? 2. What is the reason for the absence of saturation? 3. What is the effect of increasing the negative grid potential?

7. Define parts of speech, underline suffixes

relationship, important, chiefly, amplifier, safely, variation.

7. Learn the dialogue by heart

DIALOGUE

1. Did you pass your English exam successfully?

2. Yes, I did. I got an excellent mark.

   1. Was it difficult?

   2. Frankly speaking, it was. T was afraid that my English would fail¹ me.

      1. Is it true that they ask questions on speciality in English?

      2. Certainly. Besides, the examiner asked me also about my work in the students' scientific society.

         1. By the way who is your scientific guider ?

         2. Professor Smirnov is. Have you ever taken part in any scientific conference which are held annually in English at our Institute?

            1. Yes. Why²?

            2. You see, the "English teachers take it into consideration.

               1. Oh! That's very good. I took part in all conferences.

               2. What did your last report deal with?

                  1. It was about the effect of grid and plate potentials on flow of plate current. I even illustrated my report with drawings.

                  2. I think these conferences are very useful. They help to improve the foreign language.

                     1. I know that you translate many articles from English and American journals.

                     2. Yes, I do it with great interest because sometimes I find some new information there.

A. But doesn't it take too much time?

B. I remember when I started translating the original articles it really took me a lot of time and I made many mistakes, but now I have succeeded in translating them rather quickly and almost without mistakes.

2.2.10 Answer the questions to figures 3,4,5

1. What can be investigated by means of the circuit of Fig. 3? 2. When is one of the curves of Fig. 4 obtained? 3. What does Fig. 5 show?