, , . , , , , , . 25 , .
.. , , 1834 . 1850 16 , . . 1859 . .
1868 " ". , . . , . .
, 9 ( 63) . . .
350 . , . 1907 73 .
19- 20- .
. 100 , .
7. 0.
1. What was D. 1. Mendeleyev?
2. Where and when was he born?
3. What institute did he enter?
4. What subjects did he study at the institute?
5. When did he graduate from it?
6. When was he sent abroad?
7. In what year did Mendeleyev publish his Periodic Law of Elements?
8. What could the scientist predict thanks to his investigations?
9. Were these unknown elements discovered?
10. In what spheres of science did Mendeleyev carry out research?
11. When did he die?
1. D. I. Mendeleyev, the outstanding Russian scientist.
2. He was born in Tobolsk in 1834.
3. He entered the Pedagogical Institute in St. Petersburg.
4. In the institute it studied a chemistry.
5. Five years later he graduated from it.
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6. To continue his studies and research Mendeleyev was sent to Germany in 1859.
7. Mendeleyev published his Periodic Law of Elements in 1869.
8. Thanks to his investigations Mendeleyev was able to predict not only the existence of a few unknown elements but their properties as well.
9. Later the elements predicted were discovered.
10. Combining theory with practical activities he carried out enormous research in coal, iron and steel industries in Russia.
11. He died in 1907.
WORD STUDY
8. . , .
re-: to construct, to make, to build, to heat, to produce
super-: man, critical, low, to cool, to heat
sub-: group, way, normal, tropical, to divide
over-: to work, to boil, to produce, to value, to pay, pressure
semi-: automatic, conductor, official, circle
inter-: national, atomic, act, change, communication
9. , :
a lot of unsolved problems, under unusual conditions, inaccurate amount, irregular form, impossible situation, to misunderstand the drawing, to reassemble the model, to reread the article, supernatural phenomenon, to over cool the substance, to overheat the alloy, semiconductor materials, semiautomatic machine tools, intercontinental communication
, , , , , , , , , , , , , .
10. () ():
) big, plan, to tell, enormous, to have, way, investigation, to pay attention, protection, to build, to predict, to offer
) to give attention, tremendous, road, research, to construct, to forecast, to possess, scheme, to say, large, defence, to suggest
big large; plan scheme; to tell to say; enormous tremendous; to have to possess; way road; investigation research; to pay attention to give attention; protection defence; to build to construct; to predict to forecast; to offer to suggest.
11. () ():
) capable, to enter, behind, beginning, equal, to ask, to connect, hot, easy, before, similar
) cold, difficult, end, to answer, in front of, after, to disconnect, to graduate, different, unequal, incapable
capable incapable; to enter - to graduate; behind - in front of; beginning end; equal different; to ask answer; to connect - to disconnect; hot cold; easy difficult; before after; similar different.
12. , :
1. to make investigations; to make progress; two and fifteen makes seventeen; this apparatus is made of 280 pieces; a molecule is made of atoms
2. to develop industry; to develop the necessary properties; to develop a new type of device; the development of the economy; the development of new materials; the development of mechanisms
3. the number of students; a number of investigations; numbers of people; page number 55; in magazine number one; motor-car number
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4. to take a newspaper; to take interest (in); to take the form of a cylinder; to take into account; it takes me two hours to do this task; to take place; to take part
1. ; ; ; 280 ;
2. ; ; ; ; ;
3. ; ; ; 55; ;
4. ; ; ; ; , ; ;
13. :
) this thus; some same; there their; where were; very - vary; law low; form from; only the only; to furnish to finish; day date data; though through thought; read ready
) large largely; high highly; hard hardly; near nearly; short shortly; great greatly
) ; ; ; ; - ; ; ; ; ; ; ;
) ; ; ; ; ;
14. , :
1. Hydrogen and oxygen exist in nature both separately and in combination with other substances.
2. As one knows, there is neither air nor water on any part of the Moon.
3. Reaching the Earth the energy sent from the Sun is either absorbed or reflected, or both.
4. Matter can exist in either of the four states solid, liquid, gaseous or plasma.
1. .
2. , , .
3. , , , .
4. , , .
15. , , . .
1. The atmosphere of the Earth consists of various gases in varying amounts.
2. The total capacity of the new station amounts to 6,000,000 kilowatts.
3. These research centres are developing new kinds of polymer materials in order to meet the needs of various branches of industry.
4. The scientist classified the elements in the order of increasing atomic weights.
5. These articles deal with the investigations and achievement world science in the field of radioactivity.
6 A great deal of attention is paid to the study of the fundamentals of physics and mathematics at our higher educational institutions.
1. .
2. 6,000,000 .
3. - , .
4. .
5. .
6 .
18. , .
19. :
1. The first university where Rutherford studied was in...
a) America; b) Europe; c) New Zealand.
2. The university was...
a) very old and well-known all over the world;
b) very small and quite new;
c) very large and rich in traditions.
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3. At the university Rutherford became interested in...
a) physics; b) history; c) social sciences.
4. In 1908 E. Rutherford was awarded Nobel Prize for...
a) his first scientific work;
b) the practical application of his investigations;
c) a number of researches in chemistry.
Revision exercise
II. , , . .
1. In order to understand the electronic theory, () to have a clear understanding of the structure of matter.
2. () to name thousands of physical and chemical changes taking place in nature.
3. () to note that the physical form of an element has no connection with the form of the compound.
4. ( ) that this polymer changes its colour when heated.
5.( ) that the preparation of the alloy did not take much time.
6. () that such tests should be carried out in a special laboratory.
it is interesting; it should be said; it is necessary; it is possible; it is said; it can be said
1. In order to understand the electronic theory, it is necessary to have a clear understanding of the structure of matter.
2. It is possible to name thousands of physical and chemical changes taking place in nature.
3. It is interesting to note that the physical form of an element has no connection with the form of the compound.
4. It should be said that this polymer changes its colour when heated.
5. It can be said that the preparation of the alloy did not take much time.
6. It is said that such tests should be carried out in a special laboratory.
.
GRAMMAR STUDY
3. , ( ):
1. The microscope enables scientists to examine very small objects. The microscope enables very small objects to be examined in details.
2. The plasticity of steel allows metallurgists to work steel either hot or cold. The plasticity of steel allows it to be worked either hot or cold.
3. The fluidity of iron permitted the worker to cast it into an unusual shape. The fluidity of iron permitted it to be cast into an unusual form.
4. The conditions of the experiment caused the.light waves to change their frequency.
5. The great heat made the engineer utilize other working conditions.
1. . .
2. . .
3. . .
4. .
5. .
4. . .
) 1. That it is possible to convert heat to energy and energy back to heat can be demonstrated in a number of ways.
2. When we shall start a new series of experiments is not yet settled.
3. Whether the spaceship will be able to leave the earth depends upon the speed of the ship.
b) 1. One of the main characteristics of plastics is that their molecules are composed of a large number of repeating molecules known as monomers.
2. The most important feature of this plant is that all its shops are equipped with automatic and semi-automatic machine tools.
3. The difficulty is whether all the processes of the production at the plant can be mechanized.
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) 1. , , , .
2. , .
3. .
b) 1. - , , .
2. - , .
3. , .
5. , , . .
1. A few pounds of uranium 235 can supply a medium-sized town with all the electricity it needs during a whole year.
2. The atomic weight of an atom is the number of protons and neutrons it contains.
3. The phenomenon Roentgen discovered is widely used in medicine.
4. This is a type of reaction you will easily understand.
5. One of the problems Kurchatov worked at was the problem of mastering controlled thermonuclear reactions.
6. Einstein gave an entirely new idea of the world we live in.
7. The problem we are dealing with is very important for our laboratory.
8. The substance they had to work with had an unpleasant odour.
1. -235 .
2. , .
3. .
4. .
5. .
6. , .
7. , .
8. .
6. , , . national, natural, total .
.
, , - , . , , 200 , . , : . , .
- , . 1984 . . , . , , , , -60C .
, 130,000 108 .
3,100 , 2,000 , 32 . .
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7. :
1. What did M. Lomonosov say about Siberia?
2. Why is the potential of Siberian power generation unique?
3. Which is one of the main objects of Siberia development?
4. When was the construction of the BAM main line completed?
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5. Why was it difficult to build this railway?
6. How many people were engaged in the construction?
7. What is the length of the BAM main line?
8. How many bridges are there on this railway?
9. What mineral resources are extracted in the BAM zone?
10. What is BAM called?
1. Mikhail Lomonosov, a famous Russian scientist, once said that the increase of Russia's power would come from Siberia.
2. Siberia is extremely rich in natural resources,1 and the potential of Siberian power generation is truly unique: cheap coal and powerful rivers are in abundance there.
3. One of the main objects of the programme of Siberia development is to transform the region into the major national fuel and base.
4. The construction of the BAM main line was completed in 1984.
5. It runs through the taiga, huge marshes rivers.
6. When the construction work on BAM was at its height about 130,000 people of 108 different nationalities were engaged in building it.
7. The BAM main line is 3,100 km long, the total length of the tunnels is 32 km.
8. There are over 2,000 bridges on it.
9. Coking coal and iron ore, oil and gas, copper, nickel, cobalt and some other minerals are being extracted here.
10. Called here an "artery of life".
WORD STUDY
8., , :
To transform () transformer (.) transformation(.); to accelerate () accelerator (.) acceleration(.); to convert(.) converter () conversion() convertible (); to compare (.) comparison () comparative (.) comparatively (); to construct (.) constructor () construction () constructive () constructively (); to electrify () electric () electrical () electricity () electrician () electrification ()
; ; ; ; ;
9. () ():
) to finish, famous, to obtain, to convert, to apply, different, thanks to, to transmit, to permit
) to broadcast, to allow, various, to use, to transform, to complete, well-known, due to, to get
to finish - to complete; famous - well-known; to obtain - to get; to convert - to transform; to apply - to use; different various; thanks to - due to; to transmit - to broadcast; to permit - to allow.
10. () ():
) solid, increase, cheap, natural, fast, light, rich, unknown, to begin, to connect, different
) liquid, same, to complete, famous, decrease, poor, man-made, expensive, dark, to disconnect, slow
Solid - liquid, increase - decrease, cheap - expensive, natural - man-made, fast - slow, light - dark, rich - poor, unknown - famous, to begin - to complete, to connect - to disconnect, different - same
11. , :
1. The high level of nuclear physics research made it possible for Russia to become the first country to start using atomic energy for peaceful purposes.
2. The economic development of the BAM zone permits a whole series of problems to be solved.
3. The construction of the Baikal-Amur railway allowed new towns settlements and cultural centres to be built in Siberia.
4. It is necessary to have a force to cause electrons to move from their orbits.
5. It is important to find effective methods to make our star, the Sun, serve mankind.
6. The new railway lines will allow effective exploration of natural resources to be conducted in Siberia and Far East.
1. , , .
2. , .
3. - , , .
4. , .
5. , , , .
6. , .
12. , make cause.
) 1. It is obvious that if an electron absorbs energy, this energy will make it pass from one orbit to another.
2. While making calculations the engineer made some mistakes.
3. Russian physicists made some interesting reports at the last inter, national symposium of physicists.
4. This part of the device should be made of aluminum since it is to be light.
) 1. Heating can cause chemical changes.
2. Pressure causes ice to melt.
3. All her life she was devoted to the cause of women's rights.
4. Pressure in any fluid is due to one of the two causes: either compression by some sort of mechanical pumping device or the weight of the fluid itself.
) 1. , , .
2. .
3. " ", .
4. .
) 1. .
2. .
3. .
4. : - .
14. , :
1. The energy a body possesses represents its capacity to do work.
2. It is quite evident BAM will draw into economic activity vast new areas rich in natural resources.
3. The programme Russian scientists have worked out for Siberia development deludes all aspects of life in this vast region.
4. The TV programme "Vremya" Russian people watch every evening has become one of the main sources of political information in our country.
5. We may say every matter possesses energy.
1. .
2. , , .
3. .
4. "", .
5. , .
15. :
1. An important factor of Siberian power generation is that cheap coal and powerful rivers are in abundance there.
2. That the accelerated development of railroads is a requirement of our time is a well-known fact.
3. A transformer cannot be called a machine for it has no moving parts.
4. A.S. Popov invented a device which received electrical signals at great distances without any wires.
5. That Mendeleyev was right in his predictions is proved by the discovery of new elements.
6. For an electrician the most important question is whether a solid is a conductor of electricity or not.
1. .
2. - .
3. - .
4. .. , .
5. , .
6. , .
16. due to. .
1. Owing to new railway lines built in Siberia and the Far East much more natural resources will be extracted in those regions.
2. Aluminium and its alloys are very useful because of good corrosion resistance combined with their light weight.
3. Thanks to new railway lines built in Siberia its economy has been successfully developing over the last years.
1. , , .
2. .
3. , .
17. , .
18. :
1. What is the purpose of the traffic control electronic system?
a) to drive trains;
b) to improve traffic routes;
c) to make the work of traffic controllers easier.
2. What information will the computer give the controller?
a) the information on the weather conditions;
b) the full information on the conditions on the line;
c) the information on the wind direction.
3. What will the computer advise the drivers?
a) to choose necessary variants of train formation;
b) to drive freight trains;
c) with which speed they should drive trains.
19. , , :
1. The train operation system will make it possible () and regulate train traffic.
2. Computer centres exist on each ( ).
3. The computer will advise the drivers with which speed they should ( ).
4. Computers will help to () reduce the intervals of train ().
5. Traffic controllers () the movement of trains on the most intensive lines.
Considerably, railway line; drive trains; to control; movement; direct
1. The train operation system will make it possible to control and regulate train traffic.
2. Computer centres exist on each railway line.
3. The computer will advise the drivers with which speed they should drive trains.
4. Computers will help to considerably reduce the intervals of train movement.
5. Traffic controllers direct the movement of trains on the most intensive lines.
Revision Exercises
I. , one:
1. One can hardly find a sphere where power is not required.
2. One of the most useful applications of Ohm's law is the measuring of resistance.
3. Scientists develop new processes and improve old ones to produce better kinds of steel.
1. , .
2. .
3. , , .
II. , that:
1. Atomic energy can serve people but one should never forget that that energy can also destroy the world.
2. That research in the field of converting solar energy into electricity is very important today is quite evident.
3. The BAM area is nearly equal to that of Western Europe.
4. The main factor of Siberia industrial development is that large territorial production complexes are being built there.
5. It is heat that causes many chemical changes.
1. , , .
2. , , .
3. .
4. , - .
5. , .
.
GRAMMAR STUDY
2. . :
) , that, :
it is necessary
it is important -
it is desirable
it is required
1. It is important that this substance should remain liquid at the lowest temperature.
2. It is required that many new alloys having great resistance to various loading conditions (should) be developed.
3. It is necessary that the number of machine tools at our plant should be increased.
4. It is desirable that the engine should combine high efficiency and lightness.
1. , .
2. , , .
3. , .
4. , .
6) , that , :
, to order, to demand, to require
to suggest, to propose
to wish, to desire
1. They suggested that the question of applying a new method in their research should be discussed at once.
2. The engineer demanded that the materials which are to be used in the construction (should) be carefully tested.
3. We wish that you would tell us what this substance consists of.
1. , .
2. , , .
3. , , .
3. . capital, contribution, co-operation, department .
, .
TEXT A. PULKOVO RUSSIA'S MAIN OBSERVATORY
Two great observatories, Greenwich and Pulkovo, occupy a leading place among the observatories of the world.
Pulkovo is situated in a hilly area some kilometres from St. Petersburg. You can't get to Pulkovo by train: when the railway was being built the astronomers specially asked that it should be kept several kilometres away so that there should be no vibration to affect the sensitive instruments.
The work started in 1839, when the observatory was opened, and it is being continued now. This is the eternal work of astronomers to define the precise co-ordinates of the stars, to find out the exact "addresses" of heavenly bodies.
But today the scientists also conduct a time service, they study activity of the Sun, follow the flights of the Earth sputniks and calculate their orbits. The scientists of the observatory have made a valuable contribution to the study of the cosmos by observing artificial Earth satellites, man-made moons. The study of their orbits is very important for the flights of manned spaceships.
The Pulkovo observatory has a radioastronomy department equipped with modern apparatus. The big radio telescope installed there is stronger than any other telescope in the world. With the help of this powerful device the scientists of the Pulkovo observatory carry out a number of observations of Venus, Jupiter and other planets. It is necessary that before flying to other planets scientists should get the greatest possible information about the heavenly bodies.
The astronomers have obtained extremely surprising results due to radioastronomical observation. By means of the radio telescope some remarkable studies of the surface of the Sun and of solar activity have been made and a method of investigating the movement of planets has been worked out.
Astronomical observation and cosmic experiments are spheres of scientific research in which broad co-operation of scientists of various countries would be most effective.
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1839 , , . - , "" .
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. , .
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4. :
1. What two observatories occupy a leading place in the world?
2. Where is Pulkovo situated?
3. Why did the astronomers ask to keep the railway away from Pulkovo?
4. What is die eternal work of astronomers?
5. What other kinds of work do astronomers conduct now?
6. Why is it important to study the orbits of man-made satellites?
7. How do scientists at the Pulkovo observatory carry out observations of Venus, Jupiter and other planets?
1. Two great observatories, Greenwich and Pulkovo, occupy a leading place among the observatories of the world.
2. Pulkovo is situated in a hilly area some kilometres from St. Petersburg.
3. When the railway was being built the astronomers specially asked that it should be kept several kilometres away so that there should be no vibration to affect the sensitive instruments.
4. This is the eternal work of astronomers to define the precise co-ordinates of the stars, to find out the exact "addresses" of heavenly bodies.
5. Today the scientists also conduct a time service, they study activity of the Sun, follow the flights of the Earth sputniks and calculate their orbits.
6. The study of their orbits is very important for the flights of manned spaceships.
7. The big radio telescope installed there is stronger than any other telescope in the world. With the help of this powerful device the scientists of the Pulkovo observatory carry out a number of observations of Venus, Jupiter and other planets.
WORD STUDY
5. ; :
To conduct () a time service; a conductor () of electricity; a semiconductor () device; the conductivity () of this metal; the conduction () of electrons; good conductance (); conducting () capacity
; ; ; ; ; ;
To observe () stars; an accurate observation (); a careful observer (); astronomical observatory () instruments; an observable () phenomenon.
; ; ; ; .
Electrical power (); a power () station; a powerful telescope. ; ;
Technical () progress; highly skillful technician (); modern technique (). ; ;
6. , :
un-:able, obtainable, capable, productive, important, successful, natural, limited, equal, known, practical
, , , , , , , , , ,
unable, unobtainable, uncapable, unproductive, unimportant, unsuccessful, unnatural, unlimited, unequal, unknown, unpractical
, , , , , , , , , ,
in-: efficient, dependent, visible, complete, definite
, , , ,
inefficient, independent, invisible, incomplete, indefinite
, , , ,
im-: possible, pure, measurable
, ,
impossible, impure, immeasurable
, ,
non-: parallel, ferrous, conductive, metallic
, , ,
nonparallel, nonferrous, nonconductive, nonmetallic
, , ,
7. mean means :
1. Utilizing solar power on a large scale means getting possession of an immense source of power.
2. Radio and television play an important role as a means of people's political and cultural education.
3. The energy of the Sun is converted into electrical energy by means of solar batteries.
4. The high temperature research is an important problem of science. By it is by no means a new one.
5. We must by all means complete this work in time.
6. Man have tried to use solar energy since the earliest times but no means existed to generate useful power from the Sun's heat until steam engines were invented.
7. A mean solar day is the mean time during which the Earth makes one revolution round the Sun.
1. .
2. .
3. .
4. . .
5. .
6. , , , .
7. - , .
10. , :
a) 1. At the time when electricity was invented it was impossible to imagine anything more perfect. But man did not stop at electricity, he discovered another source of energy, many times more powerful the atomic energy.
2. Pressure in the centre of the Sun is some hundred billion times higher than that of the air we breathe.
3. Work is measured by product of the moving force times the distance through which the force acts.
b) 1. Russian scientists have achieved great results in nuclear physics research.
2. The flow of electrons in one direction results in producing an electric current
3. The production of high pressure gases results from a chemical reaction.
a) 1. , , - . , , .
2. , , .
3. , .
b) 1. .
2.
3. .
11. ) should would; 6) .
1. Since the Moon is much less massive than our globe, we would not weigh so much there.
2. We were suggested mat we should carefully study die properties of this solid under high temperature.
3. Without the force of gravitation there would be no pressure in liquids.
4. Before beginning an experiment one should carefully read all the instructions.
5. The steam generator is designed so that the steam generating process should be entirely automatic.
6. It would be desirable to carry out this work as soon as possible.
7. We hoped we would succeed in our experimental work.
8. Mendeleyev predicted that the missing elements would be found and would fill the blanks in his table.
9. Last year we would spend much time in the laboratory.
10. It is necessary mat the crystals of crystal clocks should vibrate in a vacuum lest air resistance should affect their vibration.
1. , , .
2. , , .
3. .
4. , .
5. , .
6. .
7. , .
8. , .
9. .
10. - , , .
12. , .
13. :
1. What is the main principle of a telescope?
a) the smaller the mirror, the brighter the reflected image;
b) the lighter the mirror, the brighter the reflected image;
c) the larger the mirror, the clearer and brighter the reflected
2. Which is the main pan of an optical telescope?
a) a revolving dome; b) a mirror; c) an electrons control unit
3. What can astronomers investigate with this unique telescope?
a) our star - the Sun: b) man-made satellites; c) the most remote bodies in the universe.
14. , , :
1. The views the telescopes give are limited by the... and... of the instruments.
2. The main principle of a telescope is the... the mirror the... the reflected image.
3. The unique telescope was... and... at the Leningrad Optical and Mechanical Association.
4. The... of the telescope mirror is 30 square metres.
5. The... of this telescope is 40-50 million times... than that of a naked eye.
6. With this telescope astronomers can... the most remote bodies in the universe.
investigate; designed; created, area; size; shape; power, larger; brighter; greater
1. The views the telescopes give are limited by the size and shape of the instruments.
2. The main principle of a telescope is the larger the mirror the brighter the reflected image.
3. The unique telescope was designed and created at the Leningrad Optical and Mechanical Association.
4. The area of the telescope mirror is 30 square metres.
5. The power of this telescope is 40-50 million times greater than that of a naked eye.
6. With this telescope astronomers can investigate the most remote bodies in the universe.
Revision Exercises
I. , :
a)1. Making an experiment with a new substance showed...
Making an experiment with a new substance, the student...
2. Carrying out observations will give...
Carrying out observations, the astronomers...
3. Exchanging TV programmes, we can
Exchanging TV programmes helps...
4. Possessing energy due to motion, the body
Possessing energy due to motion means...
5. Launching artificial satellites is...
Launching artificial satellites, we learn...
b) 1. He is producing new tools for...
Our aim is producing new tools for...
2. The scientist is completing a series of experiments in...
The task is completing a series of experiments in...
3. Man is mastering the atom's secrets.
Our purpose is mastering the atom's secrets.
a)1. ...
, ...
2. ...
, ...
3. ,
...
4. - ,
- ...
5. ...
, ...
b) 1. ...
...
2. ...
...
3. .
.
15 .
2. . :
) 1. If a solid body or a liquid is heated, it will usually expand.
2. The measurements were always correct provided the necessary instruments were used.
b) 1. Providing mercury did not expand when heated, it would not be used for taking temperatures.
2. But for electricity little could be done in a modem research laboratory.
) 1. Provided the operator's cabin had been equipped with electronic control, he would have been able to work faster and with great precision.
2. The manned spaceships might not have been launched into the cosmos unless scientists had studied the information received from the space satellites.
) 1. , . ( )
2. , . ( )
b) 1. , , .
2. - .
) 1. , . ( )
2. , , , , . ( ).
3. :
1. Were there no atmosphere, the surface of the Earth would become too hot by day and too cold at night.
2. Should the scientist use a radio telescope, he would obtain much more information about that small planet.
3. Could the observations have been proved theoretically, they would have advanced our knowledge in the field of space research.
4. Had the information been received in time, we would have used it in our calculations.
1. , .
2. -, .
3. , .
4. , .
4. .
TEXT A. WHAT IS AN ELECTRIC CURRENT?
The question is often asked: "What is an electric current?" No one has ever seen it. We only know of the existence of a current owing to its effects. A current can heat a conductor, it can have a chemical action when passing through a solution, or it can produce a magnetic effect.
We can measure currents by observing their heating, chemical or magnetic effects. The practical unit of current is called the Ampere. Two things are necessary to cause an electric current to flow: first a complete circuit, and seconda driving force1 called the electromotive force (e. m. f.).
If you put free electrons on an insulated copper ball, what would they do? In this case they would try to repel each other. In case you connected this charged ball to another ball of equal size by a copper wire, what would be the result? The electrons would move along the copper wire until the number of electrons on each ball were the same. This is an example of electromotive force causing a current to flow.
A battery has a surplus of electrons on one of its two plates; so you say that a battery furnishes an e. m. f. If a copper wire is run from one to the other, current flows in the complete circuit thus made. If a small buib is placed in the circuit, it will light up, giving evidence to a current flow. If the battery were disconnected and a generator substituted for it we should have a typical lighting system. Both batteries and generators are the most common sources of electromotive force. The practical unit of e m. f. is the Volt.
Currents will flow more readily in some substances than in others, that is, various substances offer lesser or greater resistance to the flow of current. Such substances as porcelain, ebonite, rubber, glass and the like having extremely high resistance are known as insulators. The practical unit of resistance is the Ohm.
Substances whose properties lie between those of conductors and insulators are called semiconductors. Let us name but a few most widely used at present, they are germanium, silicon, selenium and copper oxide.
The importance of semiconductors in our life cannot be overestimated. But for these tiny "workhorses" electronic industry would not have achieved such a great progress.
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1. What is the unit of current?
2. What can an electric current do?
3. What is necessary to cause an electric current to flow?
4. What are the most common sources of electromotive force?
5. How does current flow in various substances?
6. What is the unit of resistance?
7. What substances do we call insulators?
8. What semiconductors do you know?
1. The practical unit of current is called the Ampere.
2. A current can heat a conductor, it can have a chemical action when passing through a solution, or it can produce a magnetic effect.
3. Two things are necessary to cause an electric current to flow: first a complete circuit, and seconda driving force called the electromotive force (e. m. f.).
4. Both batteries and generators are the most common sources of electromotive force.
5. Currents will flow more readily in some substances than in others, that is, various substances offer lesser or greater resistance to the flow of current.
6. The practical unit of resistance is the Ohm.
7. Such substances as porcelain, ebonite, rubber, glass and the like having extremely high resistance are known as insulators.
8. Substances whose properties lie between those of conductors and insulators are called semiconductors.
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) radio and radar equipment; city water-supply system;
high-speed production process; ground-space communication station;
high-voltage transmission lines; radio-wave length stabilization
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) left-right movements; up-and-down movements; not-very-distant
future; left-hand plates; right-hand plates
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) 1. The government has provided all the necessary conditions for successful development of science.
2. The number of workshops and white plants provided with automatic control is rapidly increasing in our country.
3. Ohm's law provided the possibility of determining resistance provided the voltage and current are known.
4. Provided the Earth's mass were twice as great as it is, it would attract any body twice as strongly.
) I. Radio waves are like light waves.
2. We like working in our institute laboratories because we can always get help there in case we need it.
3. We should like to know if (whether) you have interrupted this research or not.
4. Like charges repel each other, while unlike charges attract each other.
5. Unlike solids and liquids all gases have nearly the same coefficient of expansion.
) 1. If some current flows through a thin wire and then the same amount of current is sent through a thicker one, a different amount of heat will be developed in both these wires.
2. We may say that on the Moon the weight of some body would be only 1/6 as much as it is on the Earth, its mass, however, would be certainly the same.
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