ВИВЧЕННЯ ТЕКСТУ ЗА ФАХОМ. ВИКОНАННЯ ЛЕКСИКО-ГРАМАТИЧНИХ ВПРАВ ДО ТЕМИ

2.7 Heating the Wire

A wire is known to be heated by a current flowing in it. In the process, the di fference in temperatures of the wire and the ambient atmosphere changes. At first the temperature of the wire is equal to the ambient temperature and the heat produced is spent to heat the wire. As the temperature of the wire increases, more heat is given up by the wire to the ambient atmosphere, the difference in temperatures changing.

When the heat produced by the current flow becomes equal to the heat given up, the wire temperature reaches what is known as a steady-state value. The period needed for this process depends on the devices used. For example, the' filament of an incandescent lamp reaches this value in a moment while an electric machine may reach it in several hours.

Exercises

You should spend not more than 15 min on these exercises.

I. Translate the words:

since, etc., addition, important, moving, movable, moved

II. Translate the word-combinations:

Extremely high cmrent-carrying capacity, constantly heated loads, comparatively short length of copper wire

III. Put questions to these answers:

1.1 suppose, protection should be used in any circuit. 2.1 don't know the resistivity of bronze.

IV. Use English words instead of the Russian ones:

1. Loads (используют) electric power. 2. Electric power (подается) from electric sources. 3. (Чем больше) the distance between the plates (тем меньше) is the capacity of the capacitor.

Вправа 1

Дайте відповіді на питання:

- What foreign language do you study at college?

Вправа 2

Прочитайте та перекладіть текст. Знайдіть у тексті речення з неозначеними часовими формами дієслова.

ВИВЧЕННЯ ТЕКСТУ ЗА ФАХОМ

2.8 FUSES

Fuses are widely used nowadays as protection devices. They are utilized in various circuits, electrical ecprigjnent and installations. Fuses save to protect them against overcurrents and short-circuits.

There are different types of fuses in use nowadays. Of them, quartz-sand fuses serve tor voltages up to 500 volts: fuses of this kind are produced with current ratings of 15 to 60 amp and of 100 to 350 amp.

Fuses are commonlv used in low-voltage industrial installations rated up to 1,000 v.

Fuse protection is based on a very simple principle: in ease of a short-circuit or overcurrent, when the maximum value of current has been exceeded, the fusible link, of a fuse is heated to its melting point. This opens the circuit and disconnects the circuit from the power source. In case of a fault, one should replace the faulty fusible element bu a new one.

Fuses are used both in direct current (d.c.) and alternating current (a. c.) circuits.

Exercises

I. Listen to the tape recorder and train the following words:

equipment, quartz, sand, rating, case, link, fault; sim-. pie, faulty, direct, alternating; to serve, to base, to place

II. Translate the words. Mind the prefixes:

to place-to displace-displacement; to charge-to discharge; to move-to remove; to equip-to reequip; movable-removable

III. Translate the word-combinations in writing:

quartz-sand fuse, fusible link, faulty fusible element, faulty protection device

IV. Fill in the verbs "to serve", "to reequip", "to replace":

1. The lab should be... with modern equipment. 2. This fuse cannot... as a protective element since it is faulty. It should be... with a new fuse.

V. Have a talk with your groupmate. Use in your answers "certainly", "I suppose", "I don't know":

1. Are fuses common protective devices? 2. Are they utilized in a high-voltage line? 3. Is their construction simple? Is it complex?

VI. Translate the sentences. Mind "both... and", "in case", "up to":

1. Both solid and gaseous insulators are in use nowadays. 2. In case an element gets open it should be replaced by a new one. 3. Capacitors of extremely high capacity (up to 1000 mF) are produced nowadays.

VII. Choose the correct variant:

1. A fuse serves a) as a load, b) as a protection device. 2. Fuses are used a) for d.c. only, b)for both a.c. and d.c.

3. In case of a fault a) the whole fuse should b-. replaced, b) the faulty link should be replaced.

4. Fuse protection is based on a) a simple principle, b a complex principle

VIII. Memorize the questions. Use them in a talk with your groupmate:

1. What does a fuse seive for? 2. For what type of current are fuses used? 3. What should be done in case of a faultu fuse? 4. On what principle is fuse prootection based?

Вправа 1

Дайте відповіді на питання:

- What foreign language do you study at college?

Вправа 2

Прочитайте та перекладіть текст. Знайдіть у тексті речення з неозначеними часовими формами дієслова.

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