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1. What concepts are very important in study of electric current?2. What forms an electric circuit?3. What materials are the best conductors and insulators?4. What kinds of electric circuits do you know?5. How can we open and close the circuit?6. When are electrical devices connected in series?7. What is an example of a series circuit?8. What can you say about «parallel» circuits?9. What does the short circuit often result from?VII. Talk on the types of electric circuitsUNIT 5I. Read the textAlternating CurrentCurrent is defined as increment of electrons. The unit for measuring cur-rent was named in honor of A.M. Ampere, the French physicist. Thus it iscalled ampere. The symbol for current is I. The electric current is a quantity ofelectrons flowing in a circuit per second of time. The electrons move along thecircuit because the e. m. f. drives them. The current is directly proportional tothe e. m. f.A steam of electrons in a circuit will develop a magnetic field around theconductor along which the electrons are moving. The strength of the magneticfield depends upon the current strength along the conductor. The direction ofthe field is dependant upon the direction of the current.If the force causing the electron flow is indirect, the current is called di-rect (d. c.). If the force changes its direction periodically the current is calledalternative (a. c.).Alternating current is the current that changes direction periodically. Theelectrons leave one terminal of the power supply, flow out along the conduc-tor, stop, and then flow back toward the same terminal. A voltage that causedcurrent reverses its polarity periodically. This is properly called an alternatingvoltage. The power supply that provides the alternating voltage actually re-verses the polarity of its terminals according to a fixed periodic pattern. Agiven terminal will be negative for a specific period of time and drive electronsout through the circuit. Then, the same terminal becomes positive and attractselectrons back from the circuit. This voltage source cannot be a battery. It mustconsist of some types of rotating machinery.II. Guess the meaning of the following international words:1) physicist, 2) ampere, 3) symbol, 4) second, 5) polarity, 6) period,7) battery.III. Translate into Russian the words and expression from the text:1) increment of electrons; 2) measuring; 3) to drive; 4) directly propor-tional; 5) conductor; 6) strength; 7) causing force; 8) terminal; 9) to flow;10) to reverse.IV. Give the English equivalents for the words below:1) переменный ток, 2) за секунду, 3) количество электронов, 4) потокэлектронов, 5) магнитное поле, 6) направление, 7) зависеть, 8) усиление,9) источник напряжения, 10) ротационный механизм.V. Complete the sentences using the text:1. The electric current is …2. The unit for measuring current is …3. A steam of electrons in a circuit will develop …4. The current is called direct if …5. The current is called alternating if…6. Alternating voltage is …7. Alternating voltage source cannot be …VI. Answer the questions:1. Why do electrons move along the circuit?2. What does the strength of the magnetic field depend upon?3. What does the direction of the field depend upon?
4. What is the way of alternating current electrons?5. How does the alternating voltage power supply reverse the polarity ofterminals?VI. Talk on the properties of the electric current and its typesUNIT 6I. Read the textCONDUCTORS AND INSULATORSAll substances have some ability of conducting the electric current, how-ever, they differ greatly in the ease with which the current can pass throughthem. Solid metals conduct electricity with ease while non-metals do not allowit to flow freely. Thus, there are conductors and insulators.What do the terms "conductors" and "insulators" mean?This difference is expressed by what is called electrical conductivity ofthe body. It depends upon the atomic constitution of the body. Substancesthrough which electricity is easily transmitted are called conductors. Any ma-terial that strongly resists the electric current flow is known as an insulator.Conductance, that is the conductor's ability of passing electric charges,depends on the four factors: the size of the wire used, its length and tempera-ture as well as the kind of material to be employed.A large conductor will carry the current more readily than a thinner one. Toflow through a short conductor is certainly easier for the current than through along one in spite of their being made of similar material. Hence, the longer thewire, the greater is its opposition, that is resistance, to the passage of current.There is a great difference in the conducting ability of various substances.Almost all metals are good electric current conductors. The best conductors aresilver, copper, gold and aluminum. Nevertheless, copper carries the currentmore freely than iron; and silver, in its turn, is a better conductor than copper.Copper is the most widely used conductor. The electrically operated devicesare connected to the wall socket by copper wires.A material which resists the flow of the electric current is called an insulator.The higher the opposition is, the better the insulator is. There are manykinds of insulation used to cover the wires. The kind used depends upon thepurposes the wire or cord is meant for. The insulating materials generally usedto cover the wires are rubber, asbestos, glass, plastics and others. The best in-sulators are oil, rubber and glass.Rubber covered with cotton, or rubber alone is the insulating materialusually used to cover desk lamp cords and radio cords.Glass is the insulator to be often seen on the poles that carry the telephonewires in city streets. Glass insulator strings are usually suspended from thetowers of high voltage transmission lines. One of the most important insulatorsof all, however, is air. That is why power transmission line wires are barewires depending on air to keep the current from leaking off.Conducting materials are by no means the only materials to play an im-portant part in electrical engineering. There must certainly be a conductor, thatis a path, along which electricity is to travel and there must be insulators keep-ing it from leaking off the conductor.II. Give the Russian equivalents for the words and word combinationsbelow:1) conductors; 2) insulators; 3) transmit; 4) resistance; 5) passage of cur-rent; 6) socket; 7) to connect to; 8) cord; 9) high voltage transmission line;10) leak off.III. Find in the text the sentences with the following related words andtranslate them:conducting – conductor – conductivity – conductanceIV. Make up sentences corresponding to the information given in the textCopper used to cover desk lamp cordsSilver one of the most important insulators of allRubber is the most widely used conductorGlass a better conductor than copperIron not so good conductor as copperAir the insulator usually used on the city streetpoles and high voltage transmission linesV. State questions to the underlined words:1) Solid metals conduct electricity with ease.2) Conductance depends on the four factors.
3) There are many kinds of insulation used to cover the wires.4) Insulators keep electricity from leaking off the conductor.5) Conductors play an important role in electrical engineering.VI. Say whether these sentences are true or false:1) Electrical conductivity of a body depends upon its atomic constitution.2) There is no difference in the conducting ability of various substances.3) The longer the wire is the weaker its opposition is.4) The kind of the insulating material depends upon the purpose it ismeant for.5) Conductors are substances through which electricity is easily transmitted.6) Insulators do not allow the electric current to flow freely.VII. Talk on the conducting ability of various substances and their appli-ance in electrical engineering. Use the table in Task IV.UNIT 7I. Read the textSEMICONDUCTORSThere are materials that really occupy a place between the conductors ofthe electric current and the non-conductors. They are called semiconductors.These materials conduct electricity less readily than conductors but much bet-ter than insulators.Semiconductors include almost all minerals, many chemical elements, agreat variety of chemical compounds, alloys of metals, and a number of or-ganic compounds. Like metals, they conduct electricity but they do it less ef-fectively. In metals all electrons are free and in insulators they are fixed. Insemiconductors electrons are fixed, too, but the connection is so weak that theheat motion of the atoms of a body easily pulls them away and sets them free.Minerals and crystals appear to possess some unexpected properties. It iswell known that their conductivity increases with heating and falls with cool-ing. As a semiconductor is heated, free electrons in it increase in number,hence, its conductivity increases as well.Heat is by no means the only phenomenon influencing semiconductors.They are sensitive to light, too. Take germanium as an example. Its electricalproperties may greatly change when it is exposed to light. With the help of aray of light directed at a semiconductor, we can start or stop various machines,effect remote control, and perform lots of other useful things. Just as they areinfluenced by falling light, semiconductors are also influenced by all radiation.Generally speaking, they are so sensitive that a heated object can be detectedby its radiation.Such dependence of conductivity on heat and light has opened up greatpossibilities for various uses of semiconductors. The semiconductor devicesare applied for transmission of signals, for automatic control of a variety ofprocesses, for switching on engines, for the reproduction of sound, protectionof high-voltage transmission lines, speeding up of some chemical reactions,and so on. On the one hand they may be used to transform light and heat en-ergy directly into electric energy without any complex mechanism with mov-ing .parts, and on the other hand, they are capable of generating heat or coldfrom electricity.Russian engineers and scientists turned their attention to semiconductorsmany years ago. They saw in them a means of solving an old engineeringproblem, namely, that of direct conversion of heat into electricity without boil-ers or machines. Semiconductor thermocouples created in Russia convert heatdirectly into electricity just as a complex system consisting of a steam boiler, asteam engine and a generator does it.II. Give the English equivalents for the words and word combinations be-low:1) полупроводник; 2) химическое соединение; 3) сплав; 4) освобож-дать; 5) свойство; 6) увеличивать (ся); 7) охлаждение; 8) чувствительныйк; 9) выставлять; 10) луч; 11) направлять на; 12) дистанционное управле-
ние; 13) находить, обнаруживать; 14) защита; 15) ускорение; 16) решитьинженерную проблему; 17) термоэлемент.III. Guess the meaning of the following international words:element, organic, mineral, crystal, phenomenon, automatic, control, proc-ess, reproduction, conversion, boiler.IV. Join the beginnings and ends:Semiconductors are sensitive to… … conductors of the electric currentand non-conductors.Semiconductors convert heat into … … dependence of conductivity onheat and light.Semiconductors occupy a place be- … heat and light.tween …Semiconductors conduct electricity …into electricity without machines.Great possibilities for various uses of … less effectively than metals.semiconductors are connected with …As a semiconductor is heated … … its conductivity increases as well.V. Insert words and expressions:1) Semiconductors include a great variety of (химические соединения),(сплавы металлов).2) Minerals and crystals appear to possess some unexpected (свойства).Their conductivity increases with (нагревание) and falls with (охлаждение).3) With the help of a ray of light directed at a semiconductor, we can ef-fect (дистанционное управление).4) The semiconductor devices are applied for (автоматическийконтроль) of a variety of processes, for the (воспроизведение) of sound, (ус-корение) of some chemical reactions.5) (Термоэлементы) created in Russia convert heat directly into electricity.VI. Answer the questions:1) What do semiconductors include? 2) How does the atomic structure ofsemiconductors influence their properties? 3) What phenomena influencesemiconductors? 4) What are the semiconductor devices applied for? 5) Howdo semoconductors help in solving engineering problems?VII. Talk on the properties of semiconductors and their practical applicationUNIT 8I. Read the textELECTRICITY AND MAGNETISMTEXT 1ELECTROMOTIVE FORCEWhen free electrons are dislodged from atoms, electrical energy is re-leased. Chemical reaction, friction heat and electromagnetic induction willcause electrons to move from one atom to another. Whenever energy in anyform is released, a force called electromotive (e. m. f.) is developed.If the force exerts its effort always in one direction, it is called direct; and ifthe force changes its direction of exertion periodically, it is called alternating.The chemical reaction in a dry cell, heat and friction are sources of a unidirec-tional force. Electromagnetic induction produces an alternating force. The direc-tion of force depends on the direction in which the field is cut. Whenever an e.m. f. is developed, there is also a field of energy called an electrostatic field,which can be detected by an electroscope and measured by an electrometer.TEXT 2ELECTROMAGNETIC INDUCTIONAn electromotive force is induced in the conductor when there is a changein the magnetic field surrounding a conductor. This induced electromotiveforce may be produced in several ways as follows:a. A conductor may move in a stationary magnetic field of constantstrength.b. A stationary conductor may be exposed 'to a moving magnetic field ofconstant strength.c. The strength of the field surrounding the conductor may change with-out any motion of conductor or magnetic circuit.The electromotive force induced by motion of a conductor or a magneticflux is the same when the conductor rotates and the flux is stationary or theflux rotates and the conductor is stationary. If both, conductor and flux, rotatein the same direction at the same speed, no electromotive force will be pro-duced, if they rotate at the same speed but in opposite directions, the electro-motive force induced would be twice as that which would be induced, if one ofthem was stationary. An electromotive force is not induced when a conductor
is moved parallel to the lines of force, but only when it moves at an angle withthese lines.Any motion across the direction of the lines, however, will produce anelectromotive force in the conductor. For this reason, the conductor is said to«cut» the lines of force. The actual electromotive force induced in the conduc-tor depends upon the nature at which the flux is cut.TEXT 3ELECTROMOTIVE FORCE AND RESISTANCEThe electromotive force is the very force that moves the electrons fromone point in an electric circuit towards another. In case this e. m. f. is direct,the current is direct. On the other hand, were the electromotive force alternat-ing, the current would be alternating, too. The e. m. f. is measurable and it isthe volt that is the unit used for measuring it. A current is unable to flow in acircuit consisting of metallic wires alone. A source of an e. m. f. should beprovided as well. The source under consideration may be a cell or a battery, agenerator, a thermocouple or a photocell, etc.In addition to the electromotive force and the potential difference refer-ence should be made to another important factor that greatly influences electri-cal flow, namely, resistance. All substances offer a certain amount of opposi-tion, that is to say resistance, to the passage of current. This resistance may behigh or low depending on the type of circuit and the material employed. Glassand rubber offer a very high resistance and, hence, they are considered as goodinsulators. All substances do allow the passage of some current provided thepotential difference is high enough.Certain factors can greatly influence the resistance of an electric circuit.They are the size of the wire, its length, and type. In short, the thinner orlonger the wire, the greater is the resistance offered.II. Give the English equivalents for the words below. Find in the text thesentences with these words and translate them1) трение; 2) электродвижущая сила; 3) элемент; 4) параллельное со-единение; 5) сопротивление; 6) электромагнитная индукция; 7) перемен-ный ток; 8) постоянное напряжение; 9) фотоэлемент.III. Guess the meaning of the following international words and translate them:reaction, electrostatic, electrometer, electroscope, volt, metallic.IV. Say whether these sentences are true or false:1. Alternating force always exerts its effort in one direction.2. Alternating force is produced by electromagnetic induction.3. The electromotive force is induced by motion of a conductor.4. Resistance is an important factor that greatly influences electrical flow.5. The type of the material employed doesn’t influence the resistance.V. Answer the questions:1) What factors cause the motion of electrons from one atom to another?2) When is the electromotive force developed? 3) When does an electrostaticfield appear? 4) How is the electromotive force induced? 5) What unit is usedfor measuring the electromotive force? 6) What are the sources of electromo-tive force? 7) What is called “resistance”? 8) How do the types of circuit andmaterial influence the resistance? 9) Name the factors that influence the resis-tance of an electric circuit.UNIT 9I. Read the textDYNAMOSThe term «dynamo» is applied to machines which convert either me-chanical energy into electrical energy or electrical energy into mechanical en-ergy by utilizing the principle of electromagnetic induction. A dynamo iscalled a generator when mechanical energy supplied in the form of rotation isconverted into electrical energy. When the energy conversion takes place inthe reverse order the dynamo is called a motor. Thus a dynamo is a reversiblemachine capable of operation as a generator or motor as desired.A generator does not create electricity, but generates or produces an in-duced electromotive force, which causes a current to flow through a properly
4. What is the way of alternating current electrons?5. How does the alternating voltage power supply reverse the polarity ofterminals?VI. Talk on the properties of the electric current and its typesUNIT 6I. Read the textCONDUCTORS AND INSULATORSAll substances have some ability of conducting the electric current, how-ever, they differ greatly in the ease with which the current can pass throughthem. Solid metals conduct electricity with ease while non-metals do not allowit to flow freely. Thus, there are conductors and insulators.What do the terms "conductors" and "insulators" mean?This difference is expressed by what is called electrical conductivity ofthe body. It depends upon the atomic constitution of the body. Substancesthrough which electricity is easily transmitted are called conductors. Any ma-terial that strongly resists the electric current flow is known as an insulator.Conductance, that is the conductor's ability of passing electric charges,depends on the four factors: the size of the wire used, its length and tempera-ture as well as the kind of material to be employed.A large conductor will carry the current more readily than a thinner one. Toflow through a short conductor is certainly easier for the current than through along one in spite of their being made of similar material. Hence, the longer thewire, the greater is its opposition, that is resistance, to the passage of current.There is a great difference in the conducting ability of various substances.Almost all metals are good electric current conductors. The best conductors aresilver, copper, gold and aluminum. Nevertheless, copper carries the currentmore freely than iron; and silver, in its turn, is a better conductor than copper.Copper is the most widely used conductor. The electrically operated devicesare connected to the wall socket by copper wires.A material which resists the flow of the electric current is called an insulator.The higher the opposition is, the better the insulator is. There are manykinds of insulation used to cover the wires. The kind used depends upon thepurposes the wire or cord is meant for. The insulating materials generally usedto cover the wires are rubber, asbestos, glass, plastics and others. The best in-sulators are oil, rubber and glass.Rubber covered with cotton, or rubber alone is the insulating materialusually used to cover desk lamp cords and radio cords.Glass is the insulator to be often seen on the poles that carry the telephonewires in city streets. Glass insulator strings are usually suspended from thetowers of high voltage transmission lines. One of the most important insulatorsof all, however, is air. That is why power transmission line wires are barewires depending on air to keep the current from leaking off.Conducting materials are by no means the only materials to play an im-portant part in electrical engineering. There must certainly be a conductor, thatis a path, along which electricity is to travel and there must be insulators keep-ing it from leaking off the conductor.II. Give the Russian equivalents for the words and word combinationsbelow:1) conductors; 2) insulators; 3) transmit; 4) resistance; 5) passage of cur-rent; 6) socket; 7) to connect to; 8) cord; 9) high voltage transmission line;10) leak off.III. Find in the text the sentences with the following related words andtranslate them:conducting – conductor – conductivity – conductanceIV. Make up sentences corresponding to the information given in the textCopper used to cover desk lamp cordsSilver one of the most important insulators of allRubber is the most widely used conductorGlass a better conductor than copperIron not so good conductor as copperAir the insulator usually used on the city streetpoles and high voltage transmission linesV. State questions to the underlined words:1) Solid metals conduct electricity with ease.2) Conductance depends on the four factors.
3) There are many kinds of insulation used to cover the wires.4) Insulators keep electricity from leaking off the conductor.5) Conductors play an important role in electrical engineering.VI. Say whether these sentences are true or false:1) Electrical conductivity of a body depends upon its atomic constitution.2) There is no difference in the conducting ability of various substances.3) The longer the wire is the weaker its opposition is.4) The kind of the insulating material depends upon the purpose it ismeant for.5) Conductors are substances through which electricity is easily transmitted.6) Insulators do not allow the electric current to flow freely.VII. Talk on the conducting ability of various substances and their appli-ance in electrical engineering. Use the table in Task IV.UNIT 7I. Read the textSEMICONDUCTORSThere are materials that really occupy a place between the conductors ofthe electric current and the non-conductors. They are called semiconductors.These materials conduct electricity less readily than conductors but much bet-ter than insulators.Semiconductors include almost all minerals, many chemical elements, agreat variety of chemical compounds, alloys of metals, and a number of or-ganic compounds. Like metals, they conduct electricity but they do it less ef-fectively. In metals all electrons are free and in insulators they are fixed. Insemiconductors electrons are fixed, too, but the connection is so weak that theheat motion of the atoms of a body easily pulls them away and sets them free.Minerals and crystals appear to possess some unexpected properties. It iswell known that their conductivity increases with heating and falls with cool-ing. As a semiconductor is heated, free electrons in it increase in number,hence, its conductivity increases as well.Heat is by no means the only phenomenon influencing semiconductors.They are sensitive to light, too. Take germanium as an example. Its electricalproperties may greatly change when it is exposed to light. With the help of aray of light directed at a semiconductor, we can start or stop various machines,effect remote control, and perform lots of other useful things. Just as they areinfluenced by falling light, semiconductors are also influenced by all radiation.Generally speaking, they are so sensitive that a heated object can be detectedby its radiation.Such dependence of conductivity on heat and light has opened up greatpossibilities for various uses of semiconductors. The semiconductor devicesare applied for transmission of signals, for automatic control of a variety ofprocesses, for switching on engines, for the reproduction of sound, protectionof high-voltage transmission lines, speeding up of some chemical reactions,and so on. On the one hand they may be used to transform light and heat en-ergy directly into electric energy without any complex mechanism with mov-ing .parts, and on the other hand, they are capable of generating heat or coldfrom electricity.Russian engineers and scientists turned their attention to semiconductorsmany years ago. They saw in them a means of solving an old engineeringproblem, namely, that of direct conversion of heat into electricity without boil-ers or machines. Semiconductor thermocouples created in Russia convert heatdirectly into electricity just as a complex system consisting of a steam boiler, asteam engine and a generator does it.II. Give the English equivalents for the words and word combinations be-low:1) полупроводник; 2) химическое соединение; 3) сплав; 4) освобож-дать; 5) свойство; 6) увеличивать (ся); 7) охлаждение; 8) чувствительныйк; 9) выставлять; 10) луч; 11) направлять на; 12) дистанционное управле-
ние; 13) находить, обнаруживать; 14) защита; 15) ускорение; 16) решитьинженерную проблему; 17) термоэлемент.III. Guess the meaning of the following international words:element, organic, mineral, crystal, phenomenon, automatic, control, proc-ess, reproduction, conversion, boiler.IV. Join the beginnings and ends:Semiconductors are sensitive to… … conductors of the electric currentand non-conductors.Semiconductors convert heat into … … dependence of conductivity onheat and light.Semiconductors occupy a place be- … heat and light.tween …Semiconductors conduct electricity …into electricity without machines.Great possibilities for various uses of … less effectively than metals.semiconductors are connected with …As a semiconductor is heated … … its conductivity increases as well.V. Insert words and expressions:1) Semiconductors include a great variety of (химические соединения),(сплавы металлов).2) Minerals and crystals appear to possess some unexpected (свойства).Their conductivity increases with (нагревание) and falls with (охлаждение).3) With the help of a ray of light directed at a semiconductor, we can ef-fect (дистанционное управление).4) The semiconductor devices are applied for (автоматическийконтроль) of a variety of processes, for the (воспроизведение) of sound, (ус-корение) of some chemical reactions.5) (Термоэлементы) created in Russia convert heat directly into electricity.VI. Answer the questions:1) What do semiconductors include? 2) How does the atomic structure ofsemiconductors influence their properties? 3) What phenomena influencesemiconductors? 4) What are the semiconductor devices applied for? 5) Howdo semoconductors help in solving engineering problems?VII. Talk on the properties of semiconductors and their practical applicationUNIT 8I. Read the textELECTRICITY AND MAGNETISMTEXT 1ELECTROMOTIVE FORCEWhen free electrons are dislodged from atoms, electrical energy is re-leased. Chemical reaction, friction heat and electromagnetic induction willcause electrons to move from one atom to another. Whenever energy in anyform is released, a force called electromotive (e. m. f.) is developed.If the force exerts its effort always in one direction, it is called direct; and ifthe force changes its direction of exertion periodically, it is called alternating.The chemical reaction in a dry cell, heat and friction are sources of a unidirec-tional force. Electromagnetic induction produces an alternating force. The direc-tion of force depends on the direction in which the field is cut. Whenever an e.m. f. is developed, there is also a field of energy called an electrostatic field,which can be detected by an electroscope and measured by an electrometer.TEXT 2ELECTROMAGNETIC INDUCTIONAn electromotive force is induced in the conductor when there is a changein the magnetic field surrounding a conductor. This induced electromotiveforce may be produced in several ways as follows:a. A conductor may move in a stationary magnetic field of constantstrength.b. A stationary conductor may be exposed 'to a moving magnetic field ofconstant strength.c. The strength of the field surrounding the conductor may change with-out any motion of conductor or magnetic circuit.The electromotive force induced by motion of a conductor or a magneticflux is the same when the conductor rotates and the flux is stationary or theflux rotates and the conductor is stationary. If both, conductor and flux, rotatein the same direction at the same speed, no electromotive force will be pro-duced, if they rotate at the same speed but in opposite directions, the electro-motive force induced would be twice as that which would be induced, if one ofthem was stationary. An electromotive force is not induced when a conductor
is moved parallel to the lines of force, but only when it moves at an angle withthese lines.Any motion across the direction of the lines, however, will produce anelectromotive force in the conductor. For this reason, the conductor is said to«cut» the lines of force. The actual electromotive force induced in the conduc-tor depends upon the nature at which the flux is cut.TEXT 3ELECTROMOTIVE FORCE AND RESISTANCEThe electromotive force is the very force that moves the electrons fromone point in an electric circuit towards another. In case this e. m. f. is direct,the current is direct. On the other hand, were the electromotive force alternat-ing, the current would be alternating, too. The e. m. f. is measurable and it isthe volt that is the unit used for measuring it. A current is unable to flow in acircuit consisting of metallic wires alone. A source of an e. m. f. should beprovided as well. The source under consideration may be a cell or a battery, agenerator, a thermocouple or a photocell, etc.In addition to the electromotive force and the potential difference refer-ence should be made to another important factor that greatly influences electri-cal flow, namely, resistance. All substances offer a certain amount of opposi-tion, that is to say resistance, to the passage of current. This resistance may behigh or low depending on the type of circuit and the material employed. Glassand rubber offer a very high resistance and, hence, they are considered as goodinsulators. All substances do allow the passage of some current provided thepotential difference is high enough.Certain factors can greatly influence the resistance of an electric circuit.They are the size of the wire, its length, and type. In short, the thinner orlonger the wire, the greater is the resistance offered.II. Give the English equivalents for the words below. Find in the text thesentences with these words and translate them1) трение; 2) электродвижущая сила; 3) элемент; 4) параллельное со-единение; 5) сопротивление; 6) электромагнитная индукция; 7) перемен-ный ток; 8) постоянное напряжение; 9) фотоэлемент.III. Guess the meaning of the following international words and translate them:reaction, electrostatic, electrometer, electroscope, volt, metallic.IV. Say whether these sentences are true or false:1. Alternating force always exerts its effort in one direction.2. Alternating force is produced by electromagnetic induction.3. The electromotive force is induced by motion of a conductor.4. Resistance is an important factor that greatly influences electrical flow.5. The type of the material employed doesn’t influence the resistance.V. Answer the questions:1) What factors cause the motion of electrons from one atom to another?2) When is the electromotive force developed? 3) When does an electrostaticfield appear? 4) How is the electromotive force induced? 5) What unit is usedfor measuring the electromotive force? 6) What are the sources of electromo-tive force? 7) What is called “resistance”? 8) How do the types of circuit andmaterial influence the resistance? 9) Name the factors that influence the resis-tance of an electric circuit.UNIT 9I. Read the textDYNAMOSThe term «dynamo» is applied to machines which convert either me-chanical energy into electrical energy or electrical energy into mechanical en-ergy by utilizing the principle of electromagnetic induction. A dynamo iscalled a generator when mechanical energy supplied in the form of rotation isconverted into electrical energy. When the energy conversion takes place inthe reverse order the dynamo is called a motor. Thus a dynamo is a reversiblemachine capable of operation as a generator or motor as desired.A generator does not create electricity, but generates or produces an in-duced electromotive force, which causes a current to flow through a properly