Exercises
2. (A) Give headings to each paragraph of the text; (b) explain why you have given such headings.
3. Translate the following sentences:
1. The stronger the magnetic field, the greater is the current in the armature winding. 2. The greater the speed of motion between the magnetic field and the conductors, the greater is the current in wires. 3. The thinner the wire, the greater is the developed heat. 4. The greater the number of turns of the wire, the greater is the m. m. f. 5. The faster the molecules of a substance move on heating, the farther they jump away from each other. 6. The slower the armature is rotated, the less is the output voltage.
4. Define the non-finite forms of the verb met in the text.
5. Put 10 questions to the text.
6. Translate the following sentences:
1. After studying the properties of solids we shall deal with the properties of liquids. 2. The problem to be dealt with will require much time. 3. Thermodynamics is the subject the scientist will deal with in the next article. 4. Before dealing with this new device one should study all its parts. 5. The next problem the professor dealt with was connected with the application of semiconductor lasers. 6. The work the students deal with is difficult but interesting. 7. Under ordinary conditions the only current one could deal with is a. c.
7. Speak on:
The uses of new sources of energy.
The tidal electric stations.
8. Translate the following text:
Both primary and secondary batteries and fuel cells convert chemical energy directly into electricity. In view of their limited range of application, and also the relatively low power which they supply, primary batteries will not be considered in this paper. The principles of operation of these energy-conversion devices differ basically from those in electric power stations. The main part of our electric power is derived from the combustion of coal and oil. A multi-stage process is involved. First the oxidation of the fuel produces heat, which through the steam-turbine is converted into mechanical energy and this, in its turn, drives a generator, which produces electricity.
LESSON TWENTY-FIVE
CAN SUN POWER BE USED?
Hold out your hand towards a sunbeam. It feels warm, does it not? No wonder, for only a little more than eight minutes ago it left the sun's surface whose temperature is assumed to be about 6000° С In that short period of time it has travelled about 93 million miles on its way to the earth in order to light your room, to cause the trees to grow, to produce wind energy and to create a lot of irreplaceable and wonderful things.
The
energy the earth constantly receives
from
solar radiation
is
about 35,000 times the annual energy consumption
of
mankind.
However, only a minute part of it is being utilized so far. As a
matter of fact, the conversion of solar radiation directly
into electric power by some efficient means has been the
aim
of Russian and foreign scientists, inventors, and engineers
for at least one hundred years.
Sun energy can be employed on the one hand directly as heat for space heating, water heating and certain other purposes and on the other hand it might be utilized for the production of electricity. In the latter case, electric current can be obtained as follows: 1) by using fuel for thermal power plants since the Sun is known to be the primary source of all energy stored in fuel; 2) by heating boilers or air-heaters in thermal power plants with sunbeams concentrated by collectors; 3) by converting radiation into electric voltage by means of thermocouples or photo-voltaic cells.
Generally speaking, sun energy can be utilized, too, through falling or moving water. The heat of the Sun annually evaporates millions of tons of water from the oceans, seas, and rivers, lifting it high in the air. The water vapour is then carried away to various parts of the earth where some of it falls as rain, the latter (now, water again), in its turn, flowing into rivers and back into oceans. Provided we construct a dam across the river, we create a reservoir, a so-called man-made sea. From the reservoir or waterfalls water may be directed to the hydro-electric station which houses the turbines, the generator as well as other suitable and necessary equipment. The force of the falling water rotates the blades of the turbine, the latter driving the electric generator. In this manner, the mechanical energy in running water, sometimes called white coal, is turned into electrical energy. However, we have just observed that it receives its power from the sun.
In the southern countries there are lots of solar installations. Sun heaters are used in both town and country to provide heat for various purposes. Soviet scientists designed and created valuable instruments and appliances to be operated by solar heat and light. Semiconductor photoelectric devices find a wide application both in our science and industry. As the reader is certain to remember, devices of this kind and solar batteries are usually installed in the Soviet sputniks and other spaceships.
For want of space it is impossible to mention here all our achievements in this important field of science.
Scientists all over the world will continue, of course, to look for ways of making semiconductors even more efficient. At the same time, they will do their best to find new methods of converting sun energy directly into electricity. Who knows, you or a friend of yours will perhaps be the one to come out with the best possible answer to the problem under consideration.