IV. Translate the sentences paying attention to the Infinitives and Infinitive Constructions.

1. We supposed all the details of the plan to have been explained to you long ago.

2. Yablochkov is known to be the inventor of the electric candle.

3. The method proposed by the young engineer is considered to be very effective,

4. The best way to understand the current is to see how it acts in a circuit.

5. To build up a magnetic field requires the expenditure of some amount of energy.

6. All metals are known to consist of minute particles called molecules.

7. We want you to take into consideration that voltage, resistance and capacity are the three important properties to influence the flow of current in an electric circuit.

8. We know mica and asbestos to be used as insulating materials.

9. The quantities generally measured by d.c. meters are current, voltage, power and energy. The instruments used for these purposes are known to be an ammeter, voltmeter, wattmeter.

V. Define the functions of the words underlined.

1. The appliance received required some improvement.

2. The machine used showed good results.

3. The amount of electricity generated depended on the quality of coal.

4. The methods applied improved the quality of production.

5. The experiment described attracted everybody's attention.

Lesson 2.

Text.

The Generator

You have learned, that the magnetic lines of force radiated about an electromagnet can be picked up by a coil of wire; this is known to be the principle of the induction coil. A coil of wire revolving or turning in a magnetic field also picks up the lines of force. Figure 14 shows a coil, which is rotated in a magnetic field. The ends of the coil are connected to the wires, which are not turning by means of wheels upon which there are two insulated contact surfaces. These wheels are known to be called commutators. Two brushes are installed to rub or contact the two contact surfaces of the commutator. Thus, each time the coil turns and cuts the lines of force, a pulse of current is collected by the coil, to flow out of one of the commutator contacts, to the brush contacts, and then to return through the other brush and commutator contact. See "A" and "B", Fig. 14.

There are generators, which produce direct current and those, which produce alternating current. The flow of current from the d.c. generator is always "direct". The current always flows out of one pole and back into the second pole. The flow from an a.c. generator "alternates", the current first flowing out of one pole and back to the second, then out of the second and back to the first, etc.

Words and word combinations:

to rotate –вращать, создавать завихрение

 to revolve - вращать

pick up – подбирать

surface - поверхность

to rub – тереть, натирать

radiate – излучать

commutator – коллектор, коммутатор

Assignment:

I. Make up all types of questions to the sentences:

1.The ends of the coil are connected to the wires.

2. The current always flows out of one pole and back into the second pole.

3. The wheels are known to be called commutators.

 

II. Translate the sentences paying attention to the ing-forms.

1. The new instrumеnt being developed at this plant will be tested in two weeks.

2. Two bodies having potentials of 100 volts and 50 volts, a potential difference of 50 volts exists between them.

3. Leaving the room we turn the light off.

4. An insulator is a substance, which contains no free electrons, glass, paper, rubber being the most common nonconductors.

5. Having defined two units of power, the horsepower and the kilowatt, we may use them to define two new units of work, the horsepower-hour and the kilowatt-hour.

6. The positive pole having been brought near the negative pole, the latter attracts the positive pole.

7. When rubbing a glass rod with a piece of silk, you develop a large difference of potential.

 

Lesson 3.

Text.

          Direct Current generators and its applications

The essential difference between a d. с generator and a. c. generator is that the former has a commutator by means of which the generated e. m. f. is made continuous, i. е., the com­mutator mechanically rectifies the alternating e. m. f. so that it is always of the same polarity. This is not, however, the only difference between them.

A d. с generator as well as a motor of conventional type is made up of the following parts: outer frame, or yoke, pole cores, pole coils, armature core, armature windings, commu­tator, brushes, and bearings. Of these, the yoke, pole cores, ar­mature core and the air gap between armature and pole core form the magnetic circuit while the pole coils, armature win­dings, commutator, and brushes form the electric circuit.

Generator fields may be either of two main types — sepa­rately excited or self-excited. The self-excited type is further, classified as series-wound, shunt-wound and compound-wound.

In general practice compound-wound machines are used.

Words and word combinations:

essential difference – существенная разница

d.c. generator — генератор постоянного тока

a.c. generator — генератор переменного тока

by means of which — посредством которого

the generated e.m.f. — генерируемая Э.Д.С.

I.e. = id est. = that is — то есть  

the only difference — единственная разница      

is made up — состоит    

outer frame, or yoke — внешняя рама или ярмо 
pole cores — магнитные сердечники, сердечники                  полюсов                                       

pole coils — полюсные катушки       

armature core — сердечник якоря   

armature windings — обмотки якоря

either of — любым из

separately excited — с независимым возбуждением

self-excited — самовозбуждающиеся

series-wound generator — генератор с последовательным возбуждением

shunt-wound generator — генератор с параллельным возбуждением

compound-wound generator — генератор со смешанным возбуждением, компаунд-генератор

 

II. Find the following words and word combinations in the text:

 

Lesson 4.

Text.

Electrical Motor

The principle of the electric motor is the reverse of the generator. Trace the circuit in Fig. 15. The current travels from the battery through the field coils to one of the brushes, which allows the electricity to how to one segment of commutator. Then electricity flows through the armature and out the other segment and brush.

The armature or rotating part and Held magnets becoming electromagnets, [heir poles are attracted to make the armature revolve. The brushes then slide on the simple commutator to break the circuit. The armature poles are not now attracted to the field poles because they lost their magnetism. The armature roils on around and again brushes complete the circuit lo attract the commutator to the second set of field magnets.

The "timing" or the arrangement of the brushes so that they make and break the contacts on the commutator at the proper time is very important.

There are many ways of winding and connecting armature coils. Motors are made with varied speed. For example, the vacuum-cleaner motor runs at several thousand r.p.m. (revolutions per minute), and the usual washing machine motor runs at about 1725 r.p.m.

Words and word combinations:

Assignment:

I. Find in the text the following words and word combinations: