Exercises

1. Learn the following active words and use them in the sentences of your own.

Assume считать, полагать

Blade лопасть

Boiler бойлер, паровой котел

Consumption потребление

Installation установка

Irreplaceable незаменимый

radia­tion излучение

receive получать

sunbeam солнечный луч

space, spaceship космос, космический корабль

store хранить

thermal термальный, тепловой

2. Put questions to Fig. 18.

3. Speak on possible uses of solar energy.

4. Compose a story looking at Fig. 18.

5. Answer the following questions:

1. There is black coal—the coal from the mines. Where is it used?

2. There is "white coal"—the energy of the waterfall. Where is it used?

3. There is "sky blue coal" — the energy of the wind. Where is it used?

4. There is "blue coal"—the energy of the tides of the sea Where is it used?

5. There is "yellow coal"—the energy of the sun. Where is it used?

6. Read and retell the following story:

The Sun and the Moon

Two men were arguing one day about the sun and the moon, and which of the two was more useful. At last one them said, "Oh! I know. The moon is quite worth two sun for it shines at night when it is needed, but the sun shines: the daytime when nobody wants it."

ADDITIONAL GRAMMAR EXERCISES*

The Participle

1. This brief description of some of the methods used in our work covers only a few of the problems encountered. 2. The resistance being very high, the current in the circuit was low. 3. As useful as lasers are becoming, we have hardly yet begun to realize their ultimate potentialities. 4. The test referred to above can be easily made. 5. There is always water vapour in the air, the amount depending upon various conditions. 6. Until now we have been discussing reactors from which no power is being taken. 7. The region of highest resistance is the point of contact between the pieces being welded. 8. Some of the effects produced by an electric current are discussed in the following chapter. 9. The voltage being increased, the field becomes strong enough to cause the electrons to produce addi­tional ions by collision. 10. The filament heated, the electrons leave its surface and travel to the plate. 11. Multiplying the mass of a moving body by its velocity, we shall- get its momentum. 12. These suggestions are based on practical experience gained in the design of a considerable number of laboratories not to speak of the discussions with experienced workers in the field of thermodynamics. 13. In many instances an apparatus designed for quite a different purpose was adopted, certain changes being made when required. 14. The problem having excited a great deal of discussion, a series of tests had to be carried out. 15. The oil having been exhausted, the engine stopped. 16. There are two diagrams in this figure, one of them showing the relation between volume and temperature. 17. Working at his new device, the inventor made numerous improvements, the latter resulting from his own experi­ments.

The Gerund

1. They went on studying the nature of that new phenom­enon. 2. There are different means of producing an electrical current. 3. We heard of that experiment having been started last week. 4. Radioisotopes may be used in measuring the diffusion of metals. 5. Before discussing the future development in isotope utilization, let us trace briefly the events leading to its discovery. 6. This motor is capable of effectively operat­ing completely submerged in water as a thin-shelled can completely protects the stator. 7. An unusual electric motor has been developed which creates linear motion directly without going through rotating motion first. 8. In addition to its being used as a wide-range voltmeter, the instrument can serve as an ammeter. 9. Comparing the performance of these instruments is the only means of solving the problem under discussion. 10. The trouble was due to the fact that the engine was put into operation instead of having been tested first. 11. Laboratory testing will expand rapidly at our Institute. 12. The value of the accelerating torque determines the time taken by the motor to reach full speed from the moment of switching on. 13. Some types of motor are not suit­able for braking duty, and the requirement must be specified at the time of ordering. 14. One cannot appreciate the marked improvement achieved without comparing tables II and III. 15. The machine broke on account of its having been made of a delicate material. 16. We have learned of his starting a series of new laboratory experiments. 17. Normally, stainless steels referred to above are welded without preheating and postheating.

The Infinitive

1. It is necessary that the sample to be analysed be chemi­cally pure. 2. The following precautions should be observed to insure valid results in our experiment. 3. To find an instru­ment better suited for our testing was the next problem to be solved. 4. We know the strength of a current to depend upon the resistance of the circuit. 5. For a long time the atom was thought to be indivisible. 6. A three-inch tube has been found to be satisfactory but it is entirely practicable to use

greater tubes if needed. 7. The oscillograph to be used for testing purposes is similar to that used in our laboratory. 8. If considered from this point of view, the problem seems to be rather complicated. 9. Radium is said to be one and a half million times more radioactive than uranium. 10. Tests have shown the thermometer to be very sensitive. 11. The oscillator referred to above seems to deliver only a small amount of pow­er. 12. The instrument to be described here was developed several years ago. 13. To analyze this effect is to take into consideration all the elements of the circuit. 14. To analyze this effect we shall consider all the elements of the circuit. 15. We expected the discovery to have produced great changes. 16. It is necessary to explain why the formulas given here are correct. 17. To explain that the formulas given here are correct, it is necessary to study them first. 18. To explain why the formulas given here are correct would require considerable space. 19. The apparatus to be designed is to be used at the power station. 20. This type of engine is said to have many disadvantages. 21. The effect of connecting cells in series is to increase the total voltage. 22. To find out the state of a mass of a gas is quite possible. 23. To find out the state of a mass of a gas one should know its volume, its pressure and its tem­perature. 24. The ammeter is the very instrument to measure the electric current. 25. A piece of apparatus which has the ability to maintain one of its terminals at a higher potential than the other, even though the current is allowed to flow through it, is said to develop an electromotive force. 26. To heat a body we place it in contact with another body at a higher temperature. 27. We expect most bodies to expand when heated. 28. To achieve good results we are expected to proceed in the following manner. 29. Under such conditions laboratory testing is assumed to continue to expand rapidly. 30. Todrive machines requires power.

Passive, Impersonal and Other Constructions

1. Such difficulties are often met with. 2. Three scales of 50, 100 and 250 volts have been decided upon. 3. It is necessary to point out that only brief description will be given here. 4. These capacitances are known to be inter-electrode capacitances. 5. The above possibility was not given due consideration at first. 6. It is evident that the best shielding is

obtained at 0.65 wave length. 7. One could not obtain a good knowledge of the results without repeating the test. 8. It has been established that this voltage was sufficient. 9. In the following article the different components of a cable are dealt With in turn. 10. One should keep in mind all the above-men­tioned disadvantages. 11. The device is said to have been described in some earlier papers. 12. One must always be careful when operating this machine. 13. The assistant was asked to complete the experiment. 14. He was supposed to look after the machine. 15. They employ new devices to obtain better results. 16. This machine is often made use of.

17. This invention is considered to be particularly important.

18. It is quite possible that the device under consideration will work well. 19. The new power plant is reported to have gone into operation. 20. This mechanism is believed to be the best for converting heat into work. 21. They say that the problem in question was not given due attention.

Prepositional Phrases

1. The problem of converting rotary motion to linear motion is an extremely difficult one due to the conditions just mentioned. 2. At first, this make of engine seemed to be very effective. 3. In spite of, or perhaps, because of its appar­ent simplicity, the scientific law in question is often misun­derstood. 4. The engineer made some remarks with reference to the problem under consideration. 5. The above phenomenon may be due to two causes. 6. The inventor made a new discov­ery with regard to the improvement of his engine. 7. The usual method of producing high-frequency waves is by means of vacuum tubes. 8. In view of the various sources of supply no attempt at standardizing power-station equipment was possible. 9. In the case of gases, we find that the higher the temperature, the less gas will dissolve. 10. Owing to two opposing effects, the pressure in the gas tube can be either high or low. 11. In effect, what is said with regard to one de­vice will apply to the other, as well. 12. According to the data obtained, the test was successful in spite of unfavourable conditions. 13. Galvanized iron is often used instead of alu­minium because of its cheapness. 14. Great progress has been made in science due to the discovery of the law of gravity. 15. In order to classify the elements, they are arranged in a

table in the order of increasing atomic weights and each one is assigned a number by means of which we find its position in this table. 16. Silver stands out among the tested materials thanks to its low resistance and stability. 17. Every atom is composed of at least an electron in addition to a central nucleus. 18. The apparatus, in question, broke on account of its having been made of an unsuitable material.

Modality

1. It is an increase in temperature that increases the speed of the molecules. 2. The chief requirements for silent and vibrationless running of small motors may be found in any standard textbook on mechanical design. 3. If that be true the curves should also be true. 4. Such conditions can and do occur due to shortage of generating plants in this area. 5. It was with this object in view that this device was in our laboratory. 6. If this system is to serve as a voltmeter, a resistor has to be added in series. 7. In 1870Mendeleyev arranged the elements in the form of a table and it is to Mendeleyev that we owe the present tabular form of the periodic law. 8. The brevity of the table doubtless requires that something further be said in explanation. 9. It is obvious that provided the magnetic field is produced by a coil of several turns, its intensity is much greater than if only one turn were used. 10. Naturally, this circuit can be modified if necessary. 11. Evidently, the fre­quency could be varied to meet different conditions. 12. Even now, it is impossible to say whether future improvements may not depend on the results of researches that seem unim­portant today. 13. No matter in what position the cell may be put, it will serve its purpose. 14. It is clear that the decision had to be made as to whether the uranium should be in the form of long rods. 15. One must keep in mind all the above figures. 16. Unless they apply new devices, it will be necessary to proceed as follows. 17. It was the diameter of the wire that we did change to obtain the above results. 18. It is desirable that there be only one tuning control for picture and for sound.

19. There will be no transfer of electricity between the two charged bodies provided they are joined by a glass rod.

20. Had we carried our scheme further at that time (that is 3 weeks ago), the instrument indication would have been quite different. 21. Were that liquid heated, it would greatly ex­pand.

Miscellaneous Examples

I. Having been used for a long time, the instrument partly lost its former efficiency. 2. The pressure range being beyond the limits of the existing diagram, data have been calculated by other means. 3. To do this, one proceeds as follows. 4. This prediction was given a direct proof by experiments, the results surpassing all expectations. 5. The very number of tube types may at first seem to be a source of confusion. 6. Drawing curves gives us a means of showing the relation ex­isting between the two constants. 7. Wishing to find out the cause of the fault, they examined the device in all its details. 8. The charge due to the presence of these electrons is called space charge. 9. That the beat of any pendulum is absolutely constant was first noticed by Galileo, when the scientist was a youth of nineteen. 10. By raising the filament temperature, we increase the number of emitted electrons. 11. In order to de­sign the contrivance in question, one should take into consid­eration the following factors. 12. Some 100 years ago steam engines were first introduced, the valves being hand-operated. 13. The next point to be studied is the geometry of the parts to be welded. 14. The stored energy can be dissipated in vari­ous ways, these ways having been dealt with in the previous article. 15. Phototransistors are capable of transforming the infrared solar radiations into electric current. 16. The flow of the current being reduced, the speed of the motor is correspond­ingly decreased. 17. It is evident that these curves are similar to those shown in Figs 5 and 6. 18. As for the mechanism re­ferred to above, it should be made as small as possible. 19. All heat loss was assumed to take place during combustion and expansion, the total loss amounting to 35 per cent of the avail­able heat in every instance. 20. One may surmise that were there fewer drawbacks there would be better work done. 21. It is on the above basis that all our power plants are constructed at present. 22. It should be noted that this analysis differs considerably from a recently published explanation. 23. One might expect the temperature to rise to some extent if no precautions were taken. 24. Further tests have shown the re­ceiver to be very sensitive. 25. The conditions to be satisfied here are as follows. 26. The instrument to be used for testing purposes is similar to that widely applied in the research laboratories. 26. We know of copper having been used as a conductor owing to its suitable characteristics. 27. Copper being a good conductor, we were recommended to use it when carrying on our research work. 28. In spite of all difficulties encountered the research laboratory succeeded in mastering the method under consideration. 29. During cold weather it often happens that the engine exhaust is not sufficient to supply the heating system, the radiators condensing the steam more rapidly than it can be supplied. 30. At the end of the last century, for the first time in the world, Popov trans­mitted and received electromagnetic energy over a consider­able distance without using any conductors. 31. Apart from giving mankind a powerful means of communication, Popov's work laid the foundation for further inventions leading to the creation of the modern systems of broadcasting, radiolocation and the like. 32. Although he was not the first to invent radio communication, Marconi nevertheless played an important part in developing it. 33. We know heat to pass from each particle to adjacent particles at a lower temperature. 34. Our purpose is to reduce the production cost to as low a figure as possible. 35. As previously stated, to construct such an appa­ratus is not difficult at all. 36. To master new methods of production is the aim of our research laboratory. 37. The parts to be used in the apparatus are to be previously tested. 38. Variations in this temperature affecting the final results but little, the new method of procedure was found to be entire­ly satisfactory. 39. The previously stated properties influence to a great extent the manner in which the device can most usefully be employed. 40. These series of tests were followed by others, no satisfactory results being obtained. 41. The two-way nature of force (i. е., action and reaction) holds true even though one of the objects involved moves so little that it does not seem to move at all. 42. As mentioned above some improvements have been sacrificed for the sake of obtaining the least possible size and weight. 43. These conditions per­mitted oil to be forced by a pump before starting operation. 44. On studying the nature of that new phenomenon, they were not satisfied with the results obtained and started testing various engines. 45. The amount of heat energy added as the result of agitation was found to be negligible, no rise in tem­perature being observed upon prolonged agitation, with the heater current turned off. 46. On leaving the oil separator, the exhaust steam is diverted into two parts, part of it entering the feed water heater and the remainder flowing to the heating system. 47. The effect of the test on the system may be said to have been practically negligible as far as harmful effects are concerned. 48. These materials being unsuitable for many reasons, some others must be found to replace them. 49. Max­well's equation led to Hertz discovering radio waves which, in turn, resulted in Popov inventing wireless telegraphy and all the subsequent brilliant developments in radio-engineering. 50. Thanks to the theoretical research carried out by our phys­icists and chemists, it proved possible to build atomic reac­tors provided with the proper equipment. 51. To observe is the primary rule of any experiment. 52. To prevent rust the exposed parts of the mechanism under consideration should be covered with a thick coat of paint. 53. Scientists of all countries should join their forces to make science serve peace and the well-being of mankind.

SUPPLEMENTARY READING

ENERGY

What is energy? A scientist-would say that energy is the ability to do work. You use energy when you walk. You carry your books with you to the Institute. It takes energy to carry books. You can do nothing without using energy. You wash with water warmed by energy. You put on clothes washed and ironed with energy.

There are many forms of energy. Each of these is useful to us. For example, we use heat energy to do a lot of useful things, namely, to heat our homes, to transport us from one place to another, and so on. Automobiles, trams, trains and airplanes are moved by changing heat energy to other forms of energy.

Electrical energy does many things for us. It is changed to other forms, such as: light, mechanical, heat, chemical, and others. When you watch television, you hear the sound and see the picture. The television (TV) set gets warm. Thus, electrical energy changes to heat, light and sound.

Many machines use electrical energy. They change energy from one form to another. Devices that are operated with electrical energy help us to work. Indeed, electricity plays an important part in our modern life.

ELECTRIC FISH

The electric fish is mentioned in the oldest writings of man. History tells us that the Greeks and the Romans knew about it. They knew, for example, that any man coming into contact with the electric fish could obtain an electric shock. In later years, experiments were carried out to find out the nature and amount of the shock given by one of them called the electric eel. The so-called electric eel is found in the tropi­cal waters of South America.

Small electric eels, only one inch long, can give a small shock. However, by the time they are 6 inches long their

internal battery gives as much as 200 volts. When it is quite grown a good electric eel can generate 600 volts. When it is short circuited, a current of 1 ampere can be obtained. The electricity in the electric eel seems to be produced at will. Besides, the discharges take place at speeds from 10 to 100 per second. It is interesting to mention here that the eel's head end is positive and the opposite end is negative. By the way, the electric eel has some ability for finding polarity. Thus, if two charged electrodes are placed in water, even in the dark, the electric fish which is somewhere near the elec­trodes, will move towards the positive electrode, possibly thinking that it is the head of a friend.

STEAM PRODUCES ELECTRICITY

Electrical power plants are needed in many places where water power is not available. At present only about 25 per cent of the power used in the Soviet Union is obtained from moving or falling water.

Great numbers of electric power stations throughout the country are run by the mechanical power of steam turbines. These contain large wheels with blades attached to their edges. Hot steam under great pressure is directed through nozzles against these blades. The wheels can be made to turn very fast. As many as 40 such wheels connected together may be part of a large steam turbine. A jet of high pressure steam hits the blades of one wheel, passes on to the blades of the next wheel, and so on, dropping in pressure and temperature as it pro­gresses. The jet of steam comes in at speeds as high as 1,200 miles per hour and at a temperature of 900 degrees Fahrenheit. At this temperature the first metal wheel gets red hot. By the time the steam hits the last wheel and is ready to come out el the turbine, it has dropped to a temperature of 70 degrees Fahrenheit and to a pressure of less than the pressure of the air outside. The power of the steam is thus used up completely when it turns the turbine wheels.

The turbine wheels, travelling at speeds of 600 miles per hour have very great mechanical power. This power is used to turn large coils of wire between the poles of large electromag­nets in generators. When the coils of wire are rotated very rapidly, they can generate large currents of electricity. The mechanical power of hot steam under great pressure is thus converted into great quantities of electrical energy„

How is this steam produced? In almost all of these pov plants, coal or other suitable fuel is burned to heat water a turn it into steam.

CONDUCTORS AND INSULATORS

All substances have some ability to conduct electric cur­rent, however, they differ greatly in the ease with which the current can pass through them. Substances through which electricity is easily transmitted are called conductors.

Metal is a good conductor of electric current, copper being our most commonly used conductor. That is why the electri­cally operated appliances in your home are connected to the wall socket by copper wires. Indeed, if you have turned on the light and are reading this book by an electric lamp and some­body pulls the metal wire out of the socket, the light will go out, at once. The electricity has not been turned off but it has no path to travel from the socket to your electric lamp. The flow of electrons cannot travel through space and get into an electrical device when the circuit is broken.

Not all substances can be used to conduct electric current. For example, if we use a piece of string instead of a metal wire, we find that the current stops flowing. A material like string, which does not permit electric current to flow, is called an insulator. Some commonly used insulators are air, glass, porcelain, plastics, paper, and oil. Some insulating materials used to cover wire are rubber, asbestos, lacquer and plastics.

Air is the most important of these insulators because it is the one we often rely upon. Surround your wire with plenty of space and you have built a reliable insulation. That is why transmission lines are bare wires depending on airto keep their thousands of volts in place. However, even these lines must be supported at intervals and it is the porcelain insulator that supports the wire of the transmission lines. The higher the voltage, the better should be the insulation.

Only when there is a very high voltage (high electrical pressure), which gives a strong push to the flow of electrons, they can be made to jump the air gap from one wire to another. When this does happen, a "spark" jumps the gap. Ordinarily even a small gap of air in the circuit is enough to cut off the current.

HEAT TRANSFER

Heat is a form of energy transported from one body to another because of a temperature difference. When two bodies at different temperatures are brought into contact, the warmer body will be cooled and the colder body will be warmed. In this case, heat is said to flow from the hot body to the cold body by conduction. The molecules of the hot body, being at a high­er temperature, have a higher level of kinetic energy than do the molecules of the cold body. Thus, energy is transferred through the molecules from the hot body to the cold body. The energy being transferred is called heat while it is flowing from the hot body to the cold body.4 The energy received by the cold body increases its temperature and may be stored in its molecules as an increase in molecular or internal energy.

Heat may also be transferred from one body to another through space by means of radiation. Heat is received from the Sun by any body which is exposed to the rays of the sun. The molecules of any substance at high temperature emit waves of energy which travel through the air with the speed of light. They are known to differ from light waves only in their wave lengths. The radiant energy may be absorbed and reflected by a body upon which it falls. Upon absorption, the radiant energy is stored as molecular energy in the body and a rise of temperature takes place.

Heat may be transferred from one body to another body at a distance from the first one by means of convection. In this case, a fluid is heated or cooled by conduction through contact with one body after which the fluid flows to another place where heat is transferred between moving fluid and the second body. For instance heat is transferred by conduction from the hot metal surface of a stove to a stream of moving air,, the temperature of which is increased. The heated air is then transported to a room in which the moving warm air transfers heat by conduction to the objects in the room. When heat is transferred by convection, a fluid transports the energy from one body to another through the movement of the fluid.

UNITS OF MEASUREMENT

In measuring the rate at which electrons are moving through a conductor, an electrician could say that the electric current is flowing at the rate of one coulomb per second. How-

ever, electricians have a unit which measures it directly and, therefore, instead of using the above-mentioned expres­sion, an electrician would simply say: the current is one am­pere. The ampere is the electrical unit which measures directly the quantity of electricity flowing in the conductor. The kiloampere, the largest unit of current, is equal to one thous­and amperes. Where the ampere is too large a unit to be used, we may employ the milliampere or the microampere, the prefix "milli" meaning a thousandth and "micro" standing for a mil­lionth.

Keep in mind exactly what a volt is because the term is constantly used in all branches of electrical work. It is the practical unit used to measure the pressure that causes electric current to flow through the circuit. However, it is necessary to have both larger and smaller units. Thus, we have megavolt (million volts), millivolt (a thousandth of a volt), and micro­volt, that is a millionth of a volt.

In electrical circuits, we are also interested in the magni­tude of the resistance in each conductor. I Resistance plays a very important part in the operation of every electrical circuit. For that reason, it became necessary that some special practical unit be developed which would indicate definitely how much resistance were present in any given conductor or circuit. That unit is called the ohm, a megohm equalling one million ohms arid a micro-ohm being one millionth of an ohm.

The ohm was named after an experirnentor who experi­mented with the phenomena of resistance taking place in electrical circuits. His name was George Simon Ohm. He carried on numerous experiments which demonstrated that there is a very close relationship between voltage, current, and resistance in any given circuit. He showed that the amount of current which flowed in a circuit depended both upon the amount of resistance in the circuit and the amount of voltage which caused the current to flow.

Having considered the measurement of electrical quanti­ties, we shall define now two units of heat. These are the calorie and the British thermal units. The first is a metric unit and may be defined as the average amount of heat required to raise the temperature of one gram of water one degree Centigrade. In the same way, the British thermal unit, or Btu, is the aver­age amount of heat necessary to raise the temperature of one pound of water one degree Fahrenheit. Since the calorie is a rather small quantity of heat, a larger" unit called the kilogram calorie, or large calorie, is often used. It is not difficult to understand that the kilogram calorie is 1000 times as large as the calorie which was defined above.

ELECTRON THEORY

The foundations of the modern theory of electricity were laid in the study of the electric discharge through gases, and in particular the so-called cathode rays. The nature of these cathode rays was first described by Crookes (1879) when he considered them as negatively electrified particles which were emitted from a metal under the influence of a strong electric field.

Further experiments made on these particles confirmed that they carried a negative charge and the name "electron" was given to them.

It is the movement of these electrons, whether in a conduc­tor or gas which gives rise to the phenomenon known as the electric current. The number of the electrons comprising the unit of current has been computed. At present, we know one microampere to be equal to the passage of 6 milliard electrons per second.

To keep a 100-watt lamp burning requires a flow of six milliard milliard electrons—not in a day, nor an hour, but every second. Six milliard milliard means the figure six with eighteen zeroes after it.

The reader should remember that an electron, being nega­tively charged, will move towards that end of the circuit or that part which is termed "positive". The old convention of the electric current flowing from the positive pole or end of the circuit to the negative was accepted long before the existence of the electron theory. It is in direct opposition to the real —direction of flow of electrons. The convention is, however, too firmly established and the current is still assumed to flow from positive to negative.

STEAM POWER

Steam is the principal factor in producing usable energy because of the power created by its expansion. The discovery of the power in steam produced great changes in industry.

Steam power is used mainly in the generation of electri­city. There are, however, many other examples of steam-

operated machines. There are two main types of steam machin­ery: the reciprocating engine and the turbine. In the former, steam pressure pushes against a piston connected with a crank that converts the forward and backward movement into rotary motion. In the second or turbine type, the operation is sim­ilar to that of water turbine. Jets of steam under high pressure hit the blades on the turbine wheel causing rota­tion.

The reciprocating engine develops high power at low speed while the turbine develops high power at high speed. The recip­rocating engine is often used to pump great quantities of water. The turbines are generally used in steam-electric gener­ating plants where high speed as well as great power is neces­sary. The reciprocating engine is from ten to thirty per cent efficient. Turbines usually are much more efficient because they allow a more complete expansion of steam than do recip­rocating engines.

ELECTRIC METER

How would you measure electricity? You can weigh coal. You can count apples. You can measure milk. But it is quite different with electricity because you cannot even see it. Electricity does not weigh anything. How do you measure electricity?

Well, that was not an easy question to answer, even for the scientists who tried all kinds of ways to find a suitable arrangement. But the problem was finally solved, and if you want to see how, look at your electric meter.

It does more than just measure current. It multiplies current times voltage, which is not an easy thing to do when you remember that the voltage is changing from 127 volts positive to 127 volts negative and back again 50 times a second- -. The current is also changing all the time with the demands of your electric appliances-./The multiplication of current times voltage gives watts, which is a measure of electric power.

Having the watts all figured out at any instant, the meter multiplies those by the length of time they are being used. This gives an answer in watt-hours, which is a measure of electric energy. Then as if that were not enough, the meter divides by 1000 and shows the final result of the calculation on a set of dials at any and every instant in terms of kilowatt-hours—the units in which you get electric energy.

Knowing what it has to do, one might expect a meter to be as big as a piano. But as everybody knows, it is not. Instead of it, it is a little box, starting its arithmetic lesson when you turn on a light, stopping when you turn it off

BOILING

If we heat some water in an open glass container, we can see that evaporation goes on from the top surface. This evapor­ation is indicated by the clouds forming where the vapour mixes with the colder air and condenses. We find that the temperature of water gradually rises until the thermometer registers 100°C. A little before this point is reached, bubbles appear on the sides of the container. They consist partly of gases driven from liquid and partly of water-vapour, for eva­poration is directed into the bubbles. Water is said to boil when vapour is formed both at the bottom of the container and at the top of it. The motion of the boiling water is caused by the bubbles of vapour rising through the water. The temperature of the boiling water is constant. This temperature is known as the boiling point of the liquid.

The boiling point of a liquid is the temperature at which it boils under some given pressure. When this point has been reached, further heating does not increase the temperature of the liquid, but only changes it into steam.

When water boils in a container we say that we see steam coming out of it. In fact what we see is not steam at all but fine water particles. Steam itself is invisible. It is the con­densed steam in the form of fine particles of water that we see.

As liquids always increase in volume when passing into the state of vapour, an increase in pressure always produces an increase in the boiling point.

Just as solids may under certain conditions be cooled below their melting points without freezing, so liquids may be heated above their boiling points without boiling.

Laws of Boiling

The principal laws of boiling are as follows: 1. When a liquid is heated, it begins to boil at a definite temperature, known as the boiling point, and on further heating the temperature remains constant at this value until the whole of the liquid is converted into vapour.

2. This temperature is constant for a given liquid if the pressure is constant.

3. The boiling point of a liquid increases if the pressure upon it is increased.

4. A definite quantity of heat is required to convert the unit mass of the liquid into vapour at the same temperature. This is known as the latent heat of evaporation.

APPLICATIONS OF THE ELECTROMAGNET

Electromagnets always find an application when it is de­sirable to convert electrical energy into mechanical energy.

Telegraph systems and telephones, relays, motors and generators, radio sets and television sets, electrical measuring instruments as well as thousands of other valuable and neces­sary devices are known to contain electromagnets. They may be used, as well, to protect electrical circuits against over­loads and underloads.

One of the first applications of the electromagnet was in telegraphy. Shilling, corresponding member of the Peters­burg Academy of Sciences was the first to construct the electromagnetic telegraph. He demonstrated his invention as far back as 1832.

As mentioned above, the telephone also uses electromag­nets, uses many of them, in fact. As soon as man learned to send word over the long wires of the telegraph circuit, the next problem to be solved was the telephone. Was it not pos­sible to send the spoken word over similar wires? As a matter of fact, the first practical telephone was invented by the Amer­ican scientist Bell in 1876 and was further improved by Edison.

FUSES

A fuse is a safety device that protects electric circuits from overloads. It must be put in every circuit where there is danger of overloading the line. All the current used must pass through the fuse, the latter being the weakest link in the circuit.

Such a safeguard is quite necessary. For no matter how careful you are, there is always the possible danger of a short-circuit, or an overload on some appliance. This means that an unusually large electric current will flow. If a short

circuit or overload caused more current to flow than the car­rying capacity of the wire, the wire would become hot. It might set fire to the insulation were it not for the fuse.

What actually takes place is simple enough. The fuse wire has a lower carrying capacity than the circuit it protects. Its melting temperature is low. Thus, the fuse will get hot and melt if the current becomes too great. In other words, if the current flow is greater than the carrying capacity of the fuse, the latter melts resulting in an open circuit.

As said before, all conductors have some resistance. In any conductor, heat is caused by the current's flow overcoming this resistance. The greater the current, the hotter the wire becomes. That is why the fuse melts when there is an overload The heat produced automatically stops the current flow.

If you examine several fuses, you will see that they are rated in amperes. The fuse will melt in case the current becomes greater than the rating. Therefore a I5-ampere fuse will melt and break the circuit if the current exceeds 15 amperes

Electric circuits can also be protected with circuit breakers. A circuit breaker is a switch with a heating element о a magnetic coil in it. The heating element becomes hot i the current is too great. When the element is hot, the switch opens the circuit automatically. In the other type of breaker the circuit is broken by the pull of the magnetic coil.

Circuit breakers are made in different sizes for different circuits.

THE STRUCTURE OF THE ATOM

The atom is the basic particle of all matter. All solids gases, liquids are composed of atoms.

For a time the atom was considered to be indivisible, but then it has been found that the atom in its turn can be divided into many different components.

In dividing the atom the man releases forces of great magnitude. These are forces that bind the central core of the atom This central core—the nucleus—is extremely small in diameter

The nucleus of the atom is of a highly complex structure It is the three main components of the atom that we shall deal with below. These are called protons, neutrons and electron;

The proton carries a positive charge of electricity, the number of protons in the nucleus determining the element that the atom forms.

For example, if the nucleus has a single proton, then it will form the gas hydrogen, if 92 protons are present, the element will be uranium and so on. In short, if the number of protons in the nucleus is known, the element can be found out at once.

As mentioned above, the proton carries a charge of positive electricity. We know the bodies charged with the same kind of electricity to repel one another. When two protons are brought close together they repel one another with a great force.

The second of these basic components of the nucleus is the neutron. The neutron does not carry a definite electric charge. The sub-particles that form the neutron do carry charges but the charge of one balances that of another leaving the neutron neutral. It is from this state that it gets its name.

The third component of the atom is the electron. The electrons revolve around the nucleus. Each electron carries a negative charge of electricity that is equal to the positive charge of a proton in the nucleus.

As the charge of the electron is negative and that of the proton positive, it might be thought that the proton would attract the lighter electron and draw it into the nucleus. This would happen if the electron were not revolving around the nucleus.

The speed of the electron establishes sufficient centrifugal force so that it counteracts the neutral attraction. Thus the higher the speed of the revolving electron, i. e. the greater its energy, the farther from the nucleus it will revolve.

PHOTOELECTRIC EMISSION

Electrical energy is transformed into light energy in the electric lamp. Can light energy be changed back to electrical energy? The first discovery came in 1887 when Heinrich Hertz, the prominent German scientist who is known as the "father of radio," made a great discovery. He discovered that, for a given electromotive force, an electric spark will jump across a larger gap if this gap is illuminated by ultraviolet light than if the gap is left in the dark.

The second discovery came about a year later when it was found that ultraviolet light falling upon a negatively-charged metal plate caused it to lose its charge. If the plate was charged positively, there was no apparent change. The final discovery came about ten years later when Joseph J. Tomson, the famous English scientist, discovered that ultraviolet light falling upon a metallic surface caused it to emit electron' The emission of electrons under the impact of light energy is called photoelectric emission. The more intense the light the more electrons are emitted by the exposed to light metal Although most metals will emit electrons when their surface are exposed to ultraviolet light, some metals, such as sodium potassium, and certain others, will emit electrons when exposed to ordinary visible light rays and infrared rays a well.

MAN AND HIS MACHINES

In all his activities, man now makes use of a lot of ma- chines. Although most of these are of quite recent origin, a few simple ones have come down from very ancient times

The arrow, for example, was well known to man since prehistoric times, since it was only by hunting that he could get his food. The wheel, one of the greatest inventions eve; made by man, is also of prehistoric origin. A two-wheeled carriage is represented widely in his art and literature. The lever is probably of equally ancient origin. It is mentioned by the Greek philosopher Aristotle as a means of lifting a great weight by using a very small force.

After Aristotle there was little change in the number and kind of machines in use for nearly twenty centuries. Since then one new device after another has come to displace others that were less efficient only to be displaced in turn by other devices still faster or better. Let us have a look at a few of these changes.

In going from his home in Mount Vernon to New York to be inaugurated as the first President of America, Washington travelled in a horse-drawn carriage. The roads were extremely difficult to travel. The travel of a little over two hundred miles required seven hard days. That is a speed of about 35 miles a day. Men could travel by land in only two other ways—on foot and on horseback. Within half a century of that time a few short railways had been built in three different parts of the country. At first the trains were drawn by horses; in 1831 the first steam locomotive to be used in America was put into use. The "iron horse" soon proved its efficiency. New lines were designed and old ones extended. A speed of 35 miles

a day had given way to regular schedules exceeding 35 miles an hour.

In the first decade of the present century it was thought that the limit of desirable speed had been reached. But the substitution of diesel and electric engines for steam engines and numerous other improvements have shown that much higher speeds may be easily achieved. Modern transportation uses electricity in many ways. Without it transportation, as is known today, could not exist.

On the other hand, modern life would be unthinkable without modern means of transport. To reach any part of the world is a matter of hours or days, while a century or two ago it took weeks, sometimes even months or years. Nobody could have imagined then the speed of our airplanes.

Now let us have a look at a few facts and figures concerning Moscow transport. According to historical documents one-horse cabs appeared in Moscow as early as 1586. Public trans­port was established only in the forties of the last century. The first lines for horse-drawn trams were built in 1872 and those for mechanized trams in 1903. Four years later there were already 800 trams in operation. The first eight buses appeared in the city 40 years ago, while today there are more than three thousand in operation. By the way, a Muscovite makes about 800 trips in buses, trolley-buses, the metro, and trams an­nually.

THE THERMOCOUPLE AND THE PHOTOCELL

There are two means of producing small electric currents for special purposes. One of these is the thermocouple or a thermopile. The other is the photocell, sometimes called the electric eye.

The "iron-copper" thermocouple represents an iron wire " and a copper wire, both being carefully cleaned at the end and making close contact with each other. At the point of contact between unlike metals, a current tends to flow from one metal to the other because the outer electrons in the atoms of one metal have more potential energy than those in the other metal. The measure of this potential energy difference is called potential difference. This potential difference depends both upon the nature of the metals and upon the temperature at the point of contact.

A number of thermocouples are sometimes connected in series. Such a combination called a thermopile is more sensitive than a single thermocouple.

The photocell generates a small electric current in response to the action of light. In one type, the light ejects electrons from a photosensitive surface upon which it falls. A photo­sensitive electrode usually consists of a thin layer of cesium or a cesium compound on a surface of silver. This is the photo­cell cathode. The anode is a metal rod or a loop, which, when the cell is in use, is connected to the positive terminal of a battery. It is the collector of electrons. The anode and the cathode are connected to short, light metal rods which extend through the base of the tube to form the support.

Electrons moving from the cathode to the anode constitute a small electric current whose magnitude is directly propor­tional to the amount of light falling upon the cathode.

Photocells perform a great number of very important serv­ices. Perhaps, the best-known use is in connection with motion pictures, where they are used in the reproduction of sound. They are also employed in television where they function in the transmission of the signal.

"Electric eyes" are also-used in factories to give automatic control of illumination, by turning lamps on or off as required. Traffic signals, the devices for testing, and recording the daily output of factories and many other types of safety devices are operated by photocurrents.

THE GALVANOMETER

The most important measuring instrument is the galvano­meter. It is used to detect and measure small electric currents. For the sake of simplicity it may bethought of as a d. с motor which can rotate only part of a turn because it has no commu­tator. It has a very low resistance.

The current to be measured passes through a coil which is wound around a soft-iron armature turned between the poles of a permanent magnet. A pointer attached to the coil meas­ures the rotation of the coil. A. c. cannot be used because the armature would no sooner start to rotate in one direction than the reversal of the current would start it rotating in the op­posite direction. Hence it would remain stationary.

In all of the experiments in which we use an ammeter, its connection in the circuit is always in series. This is necessary

because all the current to be measured has to pass through the ammeter. If we attempted to use a galvanometer instead of an ammeter in order to measure current, the galvanometer would be probably damaged.

There are two reasons why we cannot use the galvanometer directly in series. First, it is a sensitive instrument and is so constructed that a very low current is sufficient to move the pointer to the end of the scale. Let us assume that 0.01 ampere can move the galvanometer pointer the full scale, that is, to the end of the dial. If the current we are measuring is more than this amount, as it usually is, it is too great for the galvanometer to withstand, and the instrument, of course, is damaged.

Second, the galvanometer has a resistance of its own. Hence when we connect a galvanometer into a circuit its resistance reduces the very current it had to measure. As a result our measurements will be incorrect.

FARADAY'S DISCOVERY

Although for certain purposes we still employ batteries to a limited extent to generate the electric current, the usual procedure today is by electromagnetic induction. Great genera­tors in our power stations, driven by powerful turbines, oper­ate through the relative movement of conductors and magnets on a principle discovered in 1831 by that remarkable man, Michael Faraday.

A bookbinder's apprentice in London, Faraday was a clever boy. In the early part of 1812 he was given tickets to hear a course of lectures by Humphry Davy at the Royal Institution. At the end of the course he wrote up his notes on the lectures, bound them and sent them to the lecturer with a request that he should be employed as assistant. A few months later, at the age of twenty-two Michael Faraday was appointed to a post at the Royal Institution at 25 shillings a week. Thus, he started on that remarkable career which lasted for nearly half a century, during which he laid the founda­tions for much of our present electrical age. He became a skilful experimenter and an enthusiastic lecturer.

During the ten years or so before his great discovery, many investigators had interested themselves in the connection be­tween electricity and magnetism. It had been definitely established by Oersted's experiment that magnetism could be produced from the electric current. Why, then, could not the process be reversed and the electric current produced from magnetism?

The fulfillment of Faraday's hopes came in the year 1831 as a result of his experiments in the laboratory at the Royal Institution. We can read in his "Laboratory Notes" how, day by day, he carried on different experiments with wire and coils, permanent bar magnets and magnetic needles, with varying results.

On October 17, 1831, he discovered that if he had a coil of wire connected to a galvanometer and inserted a magnet into the coil, he obtained a deflection on the galvanometer. The coil consisted of eight windings of copper wire each 27 feet long, the windings being connected in parallel. When he was inserting one end of the magnet into the coil, he noticed that the deflection of the galvanometer continued only for a short time and stopped as soon as the magnet was completely inserted. No current was generated while the magnet remained stationary. When it was taken away, there was a second gal­vanometer deflection, but this time in the reverse direction. In both cases, however, there was a current only during the time that the magnet was moving.

PEACEFUL USES OF ATOMIC ENERGY

The splitting of the atom can either destroy all the achieve­ments of mankind all over the world or it can serve economic and cultural development of the peoples. Every country wants the atomic energy to serve the peoples living on our planet.

There are three possible ways of using atomic fission, the most outstanding discovery of physics. These are: the use of radioactive isotopes,' which are formed in nuclear processes, the use of powerful radioactive radiation, mainly in certain processes in organic chemistry, and the use of the energy re­leased during the fission of uranium and plutonium nuclei.

All these three ways are being successfully developed in our country.

The first in the world industrial atomic power plant with a 5,000 kW capacity was put into operation in the Soviet Union in 19541 This power generating installation based on the uranium graphite reactor was the creation of Kurchatov, an outstanding Russian physicist.

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