Translate the following sentences and change them according to the model given below.

Model: It is the sun that is an unlimited source of almost all kinds of energy.

The sun is an unlimited source of almost all kinds of energy.

1. Ii is in the electrical appliance that the electric energy is changed into heat.
2. It is the increase in temperature that increases the molecular motion. 3. It was Ampere who showed the difference between the current and the electrical charges. 4. It is at the power station that electricity is produced. 5. This the magnetic effect of the current that is the subject of this article. 6. It is the unit of current that is named after Ampere.

 

3.  Fill in the blanks with where, which, when, who, that:

1. We know … Oersted established the connection between an electric flow of current and a magnetic needle. 2. The great scientists Volta, Ampere and Yablochkov may be named among those … have greatly contributed to electrical engineering.
3. The end … the lines of force leave the coil after passing through its core will act like a north magnetic pole. 4. … there is a certain connection between electricity and magnetism was proved by experiments. 5. … he placed the wire parallel to the needle he saw … the needle deflected. 6. A wire … is wound in the form of a solenoid acts like a magnet as long as it is carrying a current.

 

Fill in the blanks with suitable prepositions, make up sentences with the following infinitives.

To equip …; to depend …; to compare …; to consist …; to contribute …;
to be interested …; to be familiar ….

6. Form nouns of the following verbs and translate them:

To invent, to connect, to discover, to achieve, to observe, to state, to contribute, to conduct, to produce, to operate, to deflect.

Compare:

1. Potential energy and kinetic energy.

2. A serious circuit and a parallel circuit.

3. A conductor and an insulator.

4. The magnetic effect of an electric current and the heating effect of an electric current.

 

Look at Fig. 8 and describe Oersted’s discovery.

UNIT 14

Generators

Vocabulary

to rotate |rə(ʊ)ˈteɪt| – вращать(ся)	such as |sʌtʃ| – такой как
more than – больше, чем	to operate |ˈɒpəreɪt| – управлять
to be able to – быть способным	armature |ˈɑːmətʃə| – якорь
although |ɔːlˈðəʊ| – хотя	in order to |ˈɔːdə| – для того, чтобы
cell |sel| – ячейка, батарея	revolutions per minute (r. p. m.) |ˌrevəˈluːʃənz pɜː ˈmɪnɪt| – обороты в минуту
to be unlikely |ʌnˈlʌɪkli| – маловероятно	voltage |ˈvəʊltɪdʒ| – напряжение
to supply |səˈplʌɪ| – снабжать, поставлять	to suppose |səˈpəʊz| – предполагать
purpose |ˈpəːpəs| – цель	it goes without saying – само собой разумеется
by means of |miːnz| – посредством, с помощью	irreplaceable |ɪrɪˈpleɪsəb(ə)l| – незаменимый
namely |ˈneɪmli| – а именно	to do without |wɪðˈaʊt| – обходиться без

 

Great generators in our power stations, which rotate at a constant speed day and night, summer and winter, are able to generate electric energy only because of the electromagnets. It is calculated that these machines produce more than 99.99 percent of all the world’s electric power.

Although used to operate certain devices requiring small currents for their operation, batteries and cells are unlikely to supply light, heat and power on our modern large scale. It is dynamo-electric machines that are used for this purpose. These are machines by means of which mechanical energy is turned directly electric energy with a loss of only a few per cent.

There are two types of dynamos, namely, the alternator and the generator. The former provides a. c. while the latter supplies d. c., similar to the current from a battery. Both of them must be turned by some outside source of mechanical energy, such as water power, for example. Where cities are far from water power, the mechanical energy for the generator mostly come from burning coal which operates a steam turbine which turns the generator.

Both generators and alternators consist of the following principal parts: an armature and an electromagnet. The former generally serves as a rotor in d. c. generators while it is the magnetic system that serves this purpose in alternators. The latter is usually called a stator for it is in a static condition. In order to get a strong e. m. f., the rotors in large alternators rotate at a speed of thousands of revolutions per minute (r. p. m.). In this connection one could add that the speed of rotation will control the output voltage of the generator in the following manner:

1. The faster the armature is rotated, the more voltage the generator will produce.

2. The slower the rotation, the less the output voltage.

 

Fig. 10. A modern generator

 

Electric power stations which supply electricity over long distances are at present always equipped with large alternators. These supply us with much greater quantities of current than anything ever supposed by Volta, Oersted and Ampere.

In order to produce electricity under the most economical conditions, the generators must be as large as possible. In addition to it, they should be kept as fully loaded as possible all the time.