II. Answer the following questions:

1. What made it possible to transmit electric energy over hundreds of kilometres? 2. Can electric energy be reconverted into mechanical energy? 3. What are transformers used for? 4. What do you know about the longest transmission line in prerevolutionary Russia? 5. How long is the Kuibyshev-Moscow high-tension transmission line? 6. In what way can the heating losses be reduced in transmission lines? 7. How can resistance be reduced in electric wires? 8. Why are high-voltage lines used for power transmission? 9. Is it possible to use quantum generators for power transmission?

///. Complete the following sentences:

1. Owing to the transformer it became possible ... 2. It was Ampere who ... 3. The dynamo-electric machines are used for ... 4. In order to reduce resistance in a wire, it is necessary ... 5. The waste of useful energy can be decreased... 6. Coal is burned in order to ...

IV. Define the following terms:

power station, nuclear reactor, transmission line, sole­noid, electromagnet, heat losses

V. (a) Choose the right term; (b) explain the statement:

1. The coil of wire that rotates in a dynamo or a motor is known as: (a) a turbine, (b) a stator, (c) an armature, (d) a generator.

2. Running water is an illustration of: (a) potential ener­gy, (b) kinetic energy, (c) electric energy, (d) heat energy.

3. Steam generators produce electrical energy from: (a) potential energy, (b) chemical energy, (c) light energy, (d) mechanical energy.

VI. Translate the following sentences:

I. Чем сильнее магнитное поле, тем больше ток. 2. Чем больше ток, текущий по проводнику, тем выше температура проводника. 3. Чем меньше труба, тем меньше воды про­ходит через нее. 4. Чем больше скорость движения между магнитным полем и проводниками, тем больше ток. 5. Чем короче проводник, тем меньше сопротивление проходящему току.

VII. Translate the following text:

^{STORAGE BATTERIES}

Storage batteries are made up of a number of recharge- able cells, often called secondary cells to distinguish them from primary cells. Secondary cells are made of several different materials but all work on the principle of reversible chemi- cal action between two dissimilar electrodes (plates) im- mersed in an active solution (electrolyte). Particular battery designs are, of course, much more complicated and have several plates in parallel, closely packed with insulating separators. *

VIII. Retell the text.

^{LESSON TWENTY}

PASSIVE AND IMPERSONAL CONSTRUCTIONS

Transformers

The transformer is a device for cHanging the electric cur­rent from one voltage to another. As a matter of fact, it is used for increasing or decreasing voltage. A simple trans­former is a kind of induction"poll. It is well known that in its usual form it has no moving'parts. Ori the ivhole, it requires very little mtiintenaftceprovided it is not misused and is not damaged by lightning.

We may say that the principal parts of. a transformer are: two windings, that is coils, and an iron core. They call the coil which is supplied with current the "primary winding", or just "primary", for short. The winding ifrqm .which they take the current is referred to as the "secotidary wihding" or "secondary", for short. It is not new to you that the fofrqer

is connected¹ to the source of supply, the latter being con­nected to the load, .

When the number of turns of wire on the secondary is the same as the number on the primary, the secondary vol­tage is the same as the primary, and w£ get what is called a "one-to-one" transformer. In case, ^qwever, the number of turns on the secondary winding is greater than those on the primary, the output voltage is larger than the input voltage and the transformer is called a step-up transformer. On the other hand, the secondary turns being fewer in number than the primary, the transformer is known as a step-down trans­former.