There are two types of electricity, namely, electricity at rest or in a static condition and electricity in motion, that is, the electric current. Both of them are made up of electric charges, static charges being at rest, while electric current flows and does work. Thus, they differ in their ability to serve mankind as well as in their behaviour.
Let us first turn our attention to static electricity. For a long time it was the only electrical phenomenon to be observed by man. As previously mentioned at least 2,500 years ago, or so, the Greeks knew how to get electricity by rubbing substances. However, the electricity to be obtained by rubbing objects cannot be used to light lamps, to boil water, to run electric trains, and so on. It is usually very high in voltage and difficult to control, besides it discharges in no time.
As early as 1753, Franklin made an important contribution to the science of electricity. He was the first to prove that unlike charges are produced due to rubbing dissimilar objects. To show that the charges are unlike and opposite, he decided to call the charge on the rubber— negative and that on the glass—positive.
In this connection, one might remember the Russian academician V. V. Petrov. He was the first to carry on experiments and observations on the electrification of metals by rubbing them one against another. As a result he was the first scientist in the world who solved that problem.
Who does not know that the first man to get the electric current was Volta after whom the unit of electric pressure, the volt, was named? His discovery developed out of Galvani's experiments with the frog. Galvani observed that the legs of a dead frog jumped as a result of an electric charge. He tried his experiment several times and every time he obtained the same result. He thought that electricity was generated within the leg itself.
Volta began to carry on similar experiments and soon found that the electric source was not within the frog's leg but was the result of the contact of both dissimilar metals used during his observations. However, to carry on such experiments was not an easy thing to do. He spent the next few years trying to invent a source of continuous current. To increase the effect obtained with one pair of metals, Volta increased the number of these pairs. Thus the voltaic pile consisted of a copper layer and a layer of zinc placed one above another with a layer of flannel moistened in salt water between them. A wire was connected to the first disc of copper and to the last disc of zinc.
The year 1800 is a date to be remembered: for the first time in the world's history a continuous current was generated.
Volta's Short Biography. Volta was born in Como, Italy, on February 18, 1745. For some years he was a teacher of physics in his home town. Later on he became professor of natural sciences at the University of Pavia. After his famous discovery he travelled in many countries, among them France, Germany and England. He was invited to Paris to deliver lectures on the newly discovered chemical source of continuous current. In 1819 he returned to Como where he spent the rest of his life. Volta died at the age of 82.
|
|
Exercises
I. Learn the following words, groups of words. Translate the sentences.
1. as well as — так же как. Steel as well as iron are magnetic materials.
2. at rest — в покое. A body at rest possesses potential energy.
3. behaviour — поведение; режим (работы). We observed the behaviour of gas molecules.
4. charge — заряд. What kinds of charges do you know?
5. condition — условие; состояние. Some substances change greatly under certain conditions. An object is in static condition when it does not move.
6. to control — управлять, контролировать. Students learn to control various machines.
7. copper — медь. Copper is a valuable metal.
8. to flow —течь. The electrons flow along a conductor.
9. in motion —в движении. The molecules are always in motion.
10. negative — отрицательный. He gave a negative answer.
11. opposite — противоположный. These two objects move in the opposite direction.
12. positive — положительный. A battery has a positive and a negative pole.
13. previously — заранее, предварительно. The temperature of the liquid was previously measured.
14. to remember — помнить, вспоминать. You must remember the new words.
15. the rest of — остаток; остальной. Some students of our group stayed in Moscow, the rest of them went to the country.
16. to travel — путешествовать. It is interesting to travel in summer.
17. to try — пытаться; испытывать. I shall try to solve this problem. It is necessary to try this instrument several times.
18. unlike — разноименный. A battery has unlike poles.
II. Learn to recognize the following international words.
static, voltage, control, contact, salt, disc, zinc, biography, lecture, civilization, vacuum, practical, crane, pyrometer
III. Translate the following groups of words.
negative pole, to control industrial processes, the rest of the book, hard conditions, unlike charges
в покое, управлять электрическим током, так же как, положительные заряды, противоположные полюса
IV. For the words given in (a) find the Russian equivalents in (b).
a) 1. instrument; 2. liquid; 3. means; 4. mercury; 5. purpose; 6. difference; 7. law; 8. matter; 9. heat; 10. light; 11. opposite; 12. condition; 13. flow; 14. behaviour; 15. charge
|
|
b) 1. разница, разность; 2. вещество; 3. состояние, условие; 4. заряд; 5. поток; 6. жидкость; 7. ртуть; 8. противоположный; 9. закон; 10. средство; 11. тепло; 12. цель; 13. поведение; 14. прибор; 15. свет
V. Translate the following sentences paying attention to the word in bold type.
1. The students carried out an experiment looking at the thermometer from time to time. 2. The cinema was invented before my time. 3. It is high time to begin work. 4. Four times three is twelve. 5. "Am I late?" — "No, you are just in time. " 6. "What is the time?" — "It's dinner time. " 7. The students went to the club and had a good time there. 8. It took a long time before people learned to split the atom. 9. I shall be back in no time. 10. For a long time people did not know that lightning and atmospheric electricity are one and the same thing. 11. Lomonosov lectured at the university and at the same time he worked in different fields of science. 12. I work in the laboratory two times a week.
VI. Give antonyms for the following words.
north, pole, dark, on the one hand, small, arrangement, larger, magnetized, unfamiliar, like, positive, similar, to rest, in motion
VII. Answer the following questions.
1. What types of electricity do you know? 2. What is the difference between electricity at rest and electricity in motion? 3. What kind of experiments did Galvani carry on? 4. What did Franklin prove? 5. What are the two kinds of electrical charges? 6. Who was the first to produce a continuous current? 7. What was Volta? 8. What can you say about the behaviour of static charges? 9. What did Volta's discovery result in? 10. What did Volta's device consist of? 11. Where did he spend the rest of his life?
VIII. Retell Volta's biography.
IX. Make up the annotation of the text and retell it.
LESSON ELEVEN
Read and translate the text.
ELECTRIC CURRENT
Ever since Volta first produced a source of continuous current, men of science have been forming theories on this subject. For some time they could see no real difference between the newly-discovered phenomenon and the former understanding of static charges. Then the famous French scientist Ampere (after whom the unit of current was named) determined the difference between the current and the static charges. In addition to it, Ampere gave the current direction: he supposed the current to flow from the positive pole of the source round the circuit and back again to the negative pole.
We consider Ampere to be right in his first statement but he was certainly wrong in the second, as to the direction of the current. The student is certain to remember that the flow of current is in a direction opposite to what he thought.
|
|
Let us turn our attention now to the electric current itself. The current which flows along wires consists of moving electrons. What can we say about the electron? We know the electron to be a minute particle having an electric charge. We also know that that charge is negative. As these minute charges travel along a wire, that wire is said to carry an electric current.
In addition to travelling through solids, however, the electric current can flow through liquids as well and even through gases. In both cases it produces some most important effects to meet industrial requirements.
Some liquids, such as melted metals for example, conduct current without any change to themselves. Others, called electrolytes, are found to change greatly when the current passes through them.
When the electrons flow in one direction only, the current is known to be d. c., that is, direct current. The simplest source of power for the direct current is a battery, for a battery pushes the electrons in the same direction all the time (i.e., from the negatively charged terminal to the positively charged terminal).
The letters a.с. stand for alternating current. The current under consideration flows first in one direction and then in the opposite one. The a.с. used for power and lighting purposes is assumed to go through 50 cycles in one second. One of the great advantages of a.c. is the ease with which power at low voltage can be changed into an almost similar amount of power at high voltage and vice versa. Hence, on the one hand alternating voltage is increased when it is necessary for long distance transmission and, on the other hand, one can decrease it to meet industrial requirements as well as to operate various devices at home.
Although there are numerous cases when d.c. is required, at least 90 per cent of electrical energy to be generated at present is a.c. In fact, it finds wide application for lighting, heating, industrial and some other purposes.
One cannot help mentioning here that P.N. Yablochkov (1847-1894), Russian scientist and inventor, was the first to apply a.c. in practice.
Exercises
I. Learn the following words, groups of words and sentences. Translate the sentences.
1. alternating current — переменный ток. The alternating current is used in our homes and factories.
2. as well — также. M.V. Lomonosov knew German, French, Greek and Latin as well.
3. to be certain — обязательно, несомненно. The lecture is certain to begin in time.
4. to consider — рассматривать; считать. We must consider this question as soon as possible. We consider your answer to be wrong.
5. to decrease — уменьшить, понижать. Atmospheric pressure decreases before thunderstorm.
6. to determine — определять. The students will determine the steam pressure in the turbine.
7. direction — направление. We must determine the direction of the wind.
8. direct current — постоянный ток. A battery is a source of a direct current.
9. to increase — возрастать; увеличивать. The energy needs of the world are increasing.
10. to meet requirements — удовлетворять требованиям. These instruments meet modern requirements.
11. particle — частица. What particles does the atom consist of?
12. to require — требовать. This test requires much time.
13. statement — утверждение; формулировка. Lomonosov's statements are quite correct.
14. subject — предмет; тема. We study different subjects. What is the subject of your report?
15. terminal — зажим, вывод, клемма. There are two terminals in the battery.
16. voltage — напряжение. High voltage is dangerous.
17. wire — проволока, провод. Wires are made of different metals.
II. Learn to recognize the following international words.
static, electrolyte, cycle, theory, result, thermometer, boiler, contact, fact
III. Translate the following groups of words.
to increase voltage, negative terminal, opposite direction, electrical wires, charged particles, to meet industrial requirements, important statement
интересный предмет, важное заявление, уменьшить тепло, зажим батареи, стальная проволока
IV. Answer the following questions.
1. Who first produced a source of continuous current? 2. After whom was the unit of current named? 3. Who determined the difference between the current and the static charges? 4. What did Ampere suppose? 5. What can you say about an electron? 6. What charges do you know? 7. When does a wire carry an electric current? 8. Do liquids conduct current? 9. What can you say about the electrolytes? 10. What do you call d.c.? 11. What is the advantage of a.c.? 12. Where is a.с. used? 13. Who first applied a.c.?
V. Ask your group-mate the following questions. Let him/her answer them.
1. if electricity is a form of energy. 2. if there are two types of electricity. 3. if alternating voltage can be increased and decreased. 4. if Franklin made an important contribution to the science of electricity. 5. if Ampere determined the difference between the current and the static charges. 6. if the electric current can flow through liquids and through gases. 7. if the electrolytes change greatly when the current passes through them. 8. if a negatively charged electron will move to the positive end of the wire.
VI. Put two questions to each paragraph of the text. Ask your group-mates to answer them.
VII. Find the wrong statements and correct them.
1. Electrons flow from the positively charged terminal of the battery to the negatively charged terminal. 2. Ampere supposed the current to flow from the negative pole to the positive one. 3. Static electricity is used for practical purposes. 4. Static electricity is not very high in voltage and it is easy to control it. 5. To show that the charges are unlike and opposite Franklin decided to call the charge on the rubber positive and that on the glass negative. 6. Galvani thought that electricity was generated because of the contact of the two dissimilar metals used. 7. Volta took great interest in atmospheric electricity and began to carry on experiments. 8. The direct current is known to flow first in one direction and then in the opposite one. 9. The direct current used for power and lighting purposes is assumed to go through 50 cycles a second.
VIII. Explain why:
1. Static electricity cannot be used to light lamps, to boil water, to run electric trains and so on. 2. Voltage is increased and decreased. 3. The unit of electric pressure is called the volt. 4. Students must learn English. 5. Ampere was wrong as to the current direction. 6. The current is said to flow from the positive end of the wire to its negative end.
IX. Define the following terms.
battery, alternating current, direct current, static electricity, electric current, wire, laboratory, terminal, electron
X. Make up the annotation of the text and retell it.
LESSON TWELVE
Read and translate the text.
WHAT IS HEAT?
What makes one thing hot and another cold? What do the terms "hot" and "cold" really mean?
Scientists are known to have worked for a long time to find an answer to the last question. They decided at last that the manifestation of heat was caused by a weightless substance or fluid called "caloric" which flowed from a hot body to a cold one. However, experience showed that certain heat effects could not be explained by the above theory, namely, the development of heat owing to friction as well as the temperature changes during the compression or expansion of a gas.
M. V. Lomonosov was the first to state that heat phenomena were due to molecular motion. His statement proved to be correct years after his death.
At present, we know heat to be a form of energy. Besides, we are quite familiar with the fact that all substances are made up of little particles called molecules. These are so minute that a single drop of water, for example, contains millions of them. Although a drop of water left on the table may seem to be at rest, everyone of its molecules is really moving about, colliding with other molecules, pushing them, and changing direction. Of course, while one molecule is travelling, all the other millions of molecules in the drop of water are doing the same thing.
What process takes place when we place a kettle full of cold water on the fire, in other words, when we want to heat water? The molecules begin to move much faster then, so that every time there is a collision, they jump away from each other much farther than they did before. As a result, the drop of water becomes larger, that is to say, it expands. In scientific language this property is called expansion.
The faster molecular movement makes the water first warm and then hot. On taking the kettle from the fire, we expect the molecules to slow down, and indeed the water begins to get cold. When the tea is said to be "hot" it really means that its molecules are travelling very fast. On the contrary, they are moving more slowly, when the tea is cold.
Heat and temperature are closely connected. To show that similar quantities of heat may produce different effect in different substances is not difficult at all. Placing a needle on the fire at the same time as a kettle of cold water, we find that the needle is red-hot before there is any marked difference in the water temperature.
One must say here that a red-hot needle receives far less heat than a kettle full of boiling water but its temperature is nevertheless much higher. But if we place it in the boiling water, although the latter is certain to possess far more heat than the former, the needle gives up heat to the water and not vice versa. When two bodies at different temperatures are brought into contact, we expect the warmer body to get cold while the colder one will be warmed. In this case, heat is said to flow from one body to the other by conduction.
As for expansion caused by heating, it is useless and even dangerous in some cases while in others one cannot do without it. For example, to measure temperature we employ a thermometer that is the instrument based on the expansion of bodies when heated.
Exercises
I. Learn the following words, groups of words. Translate the sentences.
1. to cause — вызывать, заставлять; причинять. Harnessing solar energy to produce electricity causes great difficulties.
2. certain — некоторый; определенный. Certain substances do not conduct the electrical current.
3. collision — столкновение. It is possible to observe the collision of molecules.
4. compression — сжатие. The gas temperature increases under compression.
5. conduction — проводимость. Copper possesses greater conduction than iron.
6. development — развитие. Great attention is paid to the development of nuclear physics.
7. effect — действие, влияние; результат. What effects of the electrical current are useful?
8. expansion — расширение, увеличение. Great expansion of research work is planned in the field of nuclear physics.
9. to expect — ожидать; рассчитывать. We expect the discovery to produce great changes.
10. to explain — объяснять. The teacher explained the problem to the students.
11. friction — трение. Friction is not always useful.
12. fire — огонь; пожар. Fire is a cause of heat. Sometimes lightning causes fire.
13. to place — помещать, класть. If you place a steel object into a magnetic field it is magnetized.
14. quantity — количество. Nuclear fuel contains great quantities of energy.
15. to take place — происходить, иметь место. What takes place inside a nuclear reactor?
16. term — термин. What new terms are used in your article?
II. Translate the following groups of words.
certain effects, expansion of gas, the development of theory, collision of particles, physical terms, to explain the laws
вызывать некоторые действия, важные термины, большое количество тепла, столкновение атомов, сжатие газов
III. Arrange the following words in pairs of antonyms.
at rest, positive, solid, right, fast, the last, useful, charge, hot, dark, negative, the first, increase, wrong, valuable, decrease, liquid, in motion, invaluable, slow, useless, discharge, cold, light
IV. Arrange the following words in pairs of synonyms.
to employ, to make, to travel, motion, similar, various, different, like, to receive, liquid, movement, to help, fluid, to assist, to do, to get, to use, to move
V. a) Form verbs from the following nouns.
increase, weight, statement, movement, difference, compression, collision, flow, application, requirement, knowledge, education, expansion, heat, water, paper
b) Use the verbs formed in sentences of your own.
VI. Translate the following questions and answer them.
1. Что такое тепло? 2. Почему предполагали, что тепло — это невесомое вещество? 3. Могли ли люди наблюдать некоторые тепловые эффекты? 4.Что происходит благодаря трению и сжатию? 5. Какие тепловые явления (phenomena) установил М.В. Ломоносов? 6. Из чего состоит вещество? 7. Как называются мельчайшие частицы вещества? 8. Что происходит, когда тело нагревается? 9. Существует ли заметная разница температур между холодным и горячим телами? 10. Какой прибор используется для измерения температуры?
VII. Make up the annotation of the text and retell it.
LESSON 13
Read and translate the text.
ELECTRIC CIRCUIT
The electric circuit is the subject to be dealt with in the present article. But what does the above term really mean? We know the circuit to be a complete path which carries the current from the source of supply to the load and then carries it again from the load back to the source.
The purpose of the electrical source is to produce the necessary electromotive force required for the flow of current through the circuit.
The path along which the electrons travel must be complete otherwise no electric power can be supplied from the source to the load. Thus we close the circuit when we switch on our electric lamp.
If the circuit is broken or, as we generally say "opened" anywhere, the current is known to stop everywhere. Hence, we break the circuit when we switch off our electrical devices. Generally speaking, the current may pass through solid conductors, liquids, gases, vacuum, or any combination of these. It may flow in turn over transmission lines from the power stations through transformers, cables and switches, through lamps, heaters, motors and so on.
There are various kinds of electric circuits such as: open circuits, closed circuits, series circuits, parallel circuits and short circuits.
To understand the difference between the following circuit connections is not difficult at all. When electrical devices are connected so that the current flows from one device to another, they are said to be connected in series. Under such conditions the current flow is the same in all parts of the circuit, as there is only a single path along which it may flow. The electrical bell circuit is considered to be a typical example of a series circuit. The parallel circuit provides two or more paths for the passage of current. The circuit is divided in such a way that part of the current flows through one path, and part through another. The lamps in your room and your house are generally
connected in parallel.
Now we shall turn our attention to the short circuit sometimes called "the short". The short circuit is produced when the current is allowed to return to the source of supply without control and without doing the work that we want it to do. The short circuit often results from cause fire because the current flows where it was not supposed to flow. If the current flow is too great a fuse is to be used as a safety device to stop the current flow.
The fuse must be placed in every circuit where there is a danger of overloading the line. Then all the current to be sent will pass through the fuse.
When a short circuit or an overload causes more current to flow than the carrying capacity of the wire, the wire becomes hot and sets fire to the insulation. If the flow of current is greater than the carrying capacity of the fuse, the fuse melts and opens the circuit.
Exercises
I. Learn the following words, groups of word. Translate the sentences.
1. cable — кабель. We tested the new cables in the high voltage laboratory.
2. to carry — нести; пропускать (ток). Who will carry the thermometer? The ability to carry electrical charges is known as conduction.
3. closed circuit — замкнутая цепь. The current flows when there is a closed circuit.
4. complete — замкнутый; полный. Тhis circuit consists of some complete paths. His answer is not complete.
5. conductor — проводник. Copper is the best conductor of electricity.
6. to deal with — иметь дело; рассматривать. Lesson 10 deals with the history of electricity.
7. fault — повреждение, авария. The fault of the electrical system was caused by lightning.
8. fuse — предохранитель. A fuse placed in an electrical circuit serves as a means of protection.
9. generally speaking — вообще говоря. Generally speaking the classification of nuclear power stations depends on the number of circuits.
10. load — нагрузка. The load of the power stations often varies.
11. open circuit — разомкнутая цепь. The current does not flow if there is an open circuit.
12. to pass — проходить; пропускать. When large currents pass through a wire it heats up.
13. safety device —предохранительное устройство. A fuse is a safety device.
14. short circuit — короткое замыкание. A short circuit is dangerous as it sometimes causes fire.
15. to supply — снабжать; подводить (ток). Our laboratory is supplied with electrical materials. This power station supplies power to our city.
16. switch — выключатель. A switch is used to break the circuit.
17. transmission line — линия электропередачи. A new high-voltage transmission line was put into operation inSiberia.
II. Translate the following groups of words.
to carry current, to deal with conductors, heat load, switches and fuses, open and complete circuits, transmission line
вообще говоря, короткое замыкание, предохранительное устройство, пропускать ток, замкнутая цепь
III. a) Give suitable prepositions where necessary, b) Form sentences with the following Infinitives.
to answer, to apply, to be interested, to contribute, to consist, to depend, to enter, to connect, to play a part, to pay attention, to go, to be followed, to carry
IV. Fill in the blanks with the words and expressions given below:
as, as well, as well as
1. It is necessary to remember the term "circuit"... it is impossible to work with electricity without circuits. 2. A short circuit may cause wire fault... cable fault. 3. Traveling through solids, the electric current can flow through liquids and gases... 4. The magnitude of the current... the voltage and resistance may vary from a small amount to a very large quantity. 5.... a cold object and a hot one are brought into contact, the former gets warmer and the latter gets colder. 6. Fuses are used... safety devices. 7.... a cold conductor becomes warmer it is unable to pass charges... it did before.
V.Ask your group-mate the following questions. Let him/her answer them.
1. if a circuit is a complete path. 2. if there are different kinds of circuits. 3. if the current can pass through liquids. 4. if we open the circuit when we switch on the light. 5. if the lamps in the room are connected in series. 6. if the fuse is a safety device. 7. if the fuse must be placed in every circuit. 8. if the current flows when the circuit is closed.
VI. Answer the following questions:
1. What is discussed in the present article? 2. What do we call an electric circuit? 3. What kinds of circuits do you know? 4. When is a "short" produced? 5. What does a short circuit often result from? 6. What safety device is used in the circuit when the current is too great? 7. What do we mean by the term "short circuit"? 8. What does the term "closed circuit" mean? 9. Why does the current flow when the circuit is closed? 10. What do you call a fuse? 11. Does the current flow when the switch is in the open position?
VII. Speak on the difference between:
1. Closed circuits and open circuits. 2. Series circuits and parallel circuits. 3. Fuses and switches.
VIII. Make up the annotation of the text and retell it.
LESSON FOURTEEN
Read and translate the text.