III. Find English equivalents.

Половина, усиливать, состоять из, с помощью, поэтому, запускать, выпрямлять.

 

 IV. Add necessary letter.

Rect-fier, di-de, resi-tance, rect-fier, opera-ion, so-rce, cond-ct, cur-ents.

   

 V. Finish the sentences.

1.Alternating current is………..

2. A half-wave rectifier consists of………………

3. The rectifier passes……………

4. Since pulsations should be eliminated………….

5. When the device operates d.c. flows………..

 

VI. Draw a scheme of a half-wave rectifier and describe its operation

VII. Answer the following questions:

 

6.How are electron tubes used?

7.What type of device is called a rectifier?

8.By what means is alternating current rectified into direct current?

9.What elements does a half-wave rectifier consist of?

10.What current should be applied to put a half-wave rectifier into opera­tion?

11.When does a half-wave rectifier pass current?

12.By what means are pulsations eliminated?

 

 

ПРАКТИЧЕСКАЯ РАБОТА № 15

                            ELECTROMAGNETIC RELAY

Цели: Введение и активизация в речи лексики по теме «Электромагнитное реле».

Оборудование: комплект тестов, раздаточный материал.

 

                                   Vocabulary

I. Learn the words and expressions.

Spring Cross-section To close Close to To move To switch on To switch off Various II. Read and translate the text.

пружина поперечное сечение замыкать, закрывать близко к (от) двигать (ся), включать выключать различный, разнообразный

 

Electromagnetic devices called relays are widely used in various branches of industry.

The main parts of a relay are an electromagnet, a spring and an ar­mature. When a current starts flowing in the electromagnet winding, the armature moves and the spring closes the contacts. The primary circuit of a relay is its electromagnet circuit and the secondary circuit is the one closed by the contacts.

When there is nocurrent in the relay's primary circuit, the spring pulls the armature and the contacts open.

Shows how a relay is used to control the work of an electric motor. The relay is placed close to the motor which is connected to its secondary circuit. The armature closes the contacts of the secondary circuit, and the motor starts operating; it will stop when the relay opens.

Without a relay, conductors with a large cross-section would have to be brought to the motor. This would be very uneconomical. The current in a relay is tens and even thousands of times smaller than that used to power the motor. Therefore, the connecting wires can have small cross-sections.

  In many systems the relay primary circuit operates automatically. Every evening and morning street lights are switched on and off from the main control panel by means of a great number of relays

 

III. Find English equivalents.

 

Близко к, движение, включать, выключать, разнообразный, пружина, поперечное сечение.

  

IV. Finish the sentences.

1. The main parts of a relay are…………

2. The primary circuit of a relay is………

3. Shows how a relay is used……..

4. The current in a relay is…………..

5. The current in a relay is………………

V. Insert the missing letters.

Ele-trom-gnetic, devi-es, wid-ly, vari-us, bran-hes, ind-stry, rel-y, ar­mat-re, win- ing, seco-dary, conta-ts.

 

VI. Complete these sentences using while. Follow the model on page 13:

1. The primary circuit of a relay is its electromagnetic circuit …...

2. When there is no current in the relay's primary circuit the contacts open…….

3. Without a relay conductors with a large cross-section should be used… ….

4. Every evening street lights are switched on… ….

 

 

 VII. Answer the following questions:

1. What are the main parts of a relay?

2. How is a relay put into operation?

3. When does the spring pull the armature?

4. What wires connect the panel with the relay?

5. By what means are street lights switched on and off?

ПРАКТИЧЕСКАЯ РАБОТА № 16

                                           FUSES

 

 

Цели:  Введение и активизация в речи лексики по теме «Плавкие предохранители».

Оборудование: комплект тестов, раздаточный материал.

 

                                    Vocabulary

I. Learn the words and expressions.

Fuse Link Fault Faulty Equipment Installation To protect To utilize To equip To serve To melt Up to II. Read and translate the text.

плавкий предохранитель звено, связь дефект, неисправность неисправный оборудование установка; защищать, предохранять использовать оборудовать, снаряжать служить плавить вплоть до

Fuses are widely used nowadays as protection devices. They are utilized in various circuits, electrical equipment and installations..Fuses serve to protect them against over currents and short-circuits.

There are different types of fuses in use nowadays. Quartz-sand fuses serve for 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 commonly used in low-voltage industrial installations rated up to 1,000 V.

Fuse protection is based on a very simple principle: in case 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 by a new one.

Fuses are used both in direct current and alternating current circuits.