MAGNETIC EFFECT OF AN ELECTRIC CURRENT

The invention of the voltaic cell in 1800 gave electri­cal experimenters a source of a constant flow of current. Seven years later the Danish scientist and experimenter, Oersted, decided to establish the relation between a flow of current and a magnetic needle. It took him at least 13 years more MAGNETIC EFFECT OF AN ELECTRIC CURRENT to find out that a compass needle is deflected when brought near a wire through which the electric current flows. At last, during a lecture he adjusted, by chance, the wire parallel to the needle. Then, both he and his class saw that when the current was turned on, the needle deflected MAGNETIC EFFECT OF AN ELECTRIC CURRENT almost at right angles towards the conductor. As soon as the direction of the current was reversed, the direction the needle pointed in was reversed too. Oersted also pointed out that if the wire were ad­justed below the needle, the deflection was reversed.

The above-mentioned MAGNETIC EFFECT OF AN ELECTRIC CURRENT phenomenon highly interested Ampere who repeated the experiment and added a number of valuable observations and statements. He began his research under the influence of Oersted's discovery and carried it on throughout the rest of his life.

Everyone knows the rule thanks to which we can always find the MAGNETIC EFFECT OF AN ELECTRIC CURRENT direction of the magnetic effect of the current. It is known as Ampere's rule. Ampere established and proved that magnetic effects could be produced without any magnets by means of electricity alone. He turned his attention to the behaviour of the electric current in a single straight conductor MAGNETIC EFFECT OF AN ELECTRIC CURRENT and in a conductor that is formed into a coil, i.e. a solenoid.

When a wire conducting a current is formed into a coil of several turns, the amount of magnetism is greatly in­creased.

It is not difficult to understand that the greater the number MAGNETIC EFFECT OF AN ELECTRIC CURRENT of turns of wire, the greater is the m.m.f. (that is the magnetomotive force) produced within the coil by any constant amount of current flowing through it. In addition, when doubling the current, we double the magnetism gener­ated in the coil.

A solenoid has two poles MAGNETIC EFFECT OF AN ELECTRIC CURRENT which attract and repel the poles of other magnets. While suspended, it takes up a north and a south direction exactly like the compass needle. A coreof iron becomes strongly magnetized if placed with­in the solenoid while the current is flowing.

When winding a coil of wire on an iron MAGNETIC EFFECT OF AN ELECTRIC CURRENT core, we obtain an electromagnet. That the electromagnet is a controllable and reliable magnet is perhaps known to everyone. It is, so to say, a temporary magnet provided by electricity. Its behaviour is very simple. The device is lifeless unless an electric current flows through the coil MAGNETIC EFFECT OF AN ELECTRIC CURRENT. However, the de­vice comes to life if the current flows. The iron core will act as a magnet as long as the current continues to pass along the winding.

I. Learn the following words, groups of words. Translate the sentences.

1.to add— добавлять, ложить. When we add heat temperature rises.

2.at MAGNETIC EFFECT OF AN ELECTRIC CURRENT right angles— под прямым углом. The magnetic and the electrical fields act at right angles to each other.

3.to adjust— регулировать; устанавливать. We must adjust the voltage before our experiment. The student adjusted a thermometer above a heated body.

4. as soon as — как. The current will flow as soon MAGNETIC EFFECT OF AN ELECTRIC CURRENT as you close the circuit.

5. coil— катушка. Let us pass the current through the coil.

6. constant— неизменный. The temperature of boiling water does not change at constant pressure.

7.core— сердечник. The core of the electromagnet is usually мейд of iron.

8. to establish— устанавливать, основывать. Who es­tablished MAGNETIC EFFECT OF AN ELECTRIC CURRENT the relation between current and resistance?

9. to find out— выяснять; осознавать. Who found out the relation between electricity and magnetism?

10. needle— стрелка. The compass needle always points to the North.

11. to reverse— изменять на оборотное, реверсировать. If the resistance is reversed the current in the circuit is reversed too.

12. to MAGNETIC EFFECT OF AN ELECTRIC CURRENT repel— отталкивать. Like poles of the magnet repel each other.

13. rule — правило. Why did you not learn grammar rules?

14. straight— прямой. This article deals with a straight conductor carrying a current.

15. turn — виток. The coil may contain several turns of wire.

16. to turn on — включать. In the evening MAGNETIC EFFECT OF AN ELECTRIC CURRENT I turn the TV on.

II.Learn to recognize the following international words.

magnetic, compass, parallel, effect, magnet, magnetism, solenoid, electromagnet, process, electricity

III. Translate the following groups of words.

to adjust the instrument, constant temperature, coil of wire, iron core, to reverse the direction, principal rule

железная стрелка, прямой проводник, как, под MAGNETIC EFFECT OF AN ELECTRIC CURRENT прямым углом, изменять направление, установить разницу

IV. Translate the following sentences and define the functions of the word that.

1. It is clear that the greater the number of free elec­trons in a substance, the better that substance conducts the electric current. 2. An electric current passing through a wire MAGNETIC EFFECT OF AN ELECTRIC CURRENT heats that wire. 3. It is the unit of current that is named after Ampere. 4. That a solenoid has two poles that attract and repel the poles of other magnets is a well-known fact. 5. The physics of bodies at rest is much simpler than that of the bodies that MAGNETIC EFFECT OF AN ELECTRIC CURRENT are in motion. 6. There was a time when lightning was a problem that scientists tried to solve but at present everybody knows that it is an electric spark like that produced by the electric machines. 7. Experiments show that all gases expand when heated.

V. Fill in the MAGNETIC EFFECT OF AN ELECTRIC CURRENT blanks with suitable words given below:

where, which, when, who, that

1. We know ... Oersted established the relation be­tween the flow of electric current and a magnetic needle. 2. The great scientists Volta, Ampere and P. N. Yablochkov may be named among those ... have greatly contributed to electri­cal engineering. 3. The MAGNETIC EFFECT OF AN ELECTRIC CURRENT end ... the lines of force leave the coil after passing through its core will act like a north magnetic pole. 4. ... there is a certain connection between electricity and magnetism was proved by experiments. 5. ... he placed the wire parallel to the needle he saw ... the needle deflected. 6. A wire ... is wound MAGNETIC EFFECT OF AN ELECTRIC CURRENT in the form of a solenoid acts like a magnet as long as it is carrying a current.

VI. Translate the following sentences paying attention to the words in bold type.

a) 1. Ampere's contribution to electrodynamics ashecalled the new science began in 1820. 2. As it is impossi­ble to detect MAGNETIC EFFECT OF AN ELECTRIC CURRENT electricity by our physical senses, we generally detect it by its effects. 3. An electromagnet loses its mag­netic properties as soon as the current is turned off. 4. In certain branches of industry, chemical energy is not sowidely used asmechanical energy. 5. The average speed of all molecules remains the MAGNETIC EFFECT OF AN ELECTRIC CURRENT same as long as the temperature is constant. 6. In order to produce electricity more econom­ically the generators must be as large as possible. 7. As a gas is cooled, it loses heat as well asenergy. 8. The magnet­ic effect of an electric current is the subject of the present article MAGNETIC EFFECT OF AN ELECTRIC CURRENT, as forthe heating effect it was dealt with before.

b) 1. Rubber is a very poorconductor of electricity. 2. This is the veryappliance which I need for my experi­ment. 3. M. V. Lomonosov was born in the family of a poorpeas­ant. 4. All metals are poorinsulators of electric current. 5. Electricity at MAGNETIC EFFECT OF AN ELECTRIC CURRENT restor in a static condition does no work. 6. Heat causes many chemi­cal reactions. 7. What causesthe electrons to flow along the wire? 8. A short circuit may be the cause of fire.

VII. Give suitable prepositions to the following verbs and form sen­tences with them.

to equip, to MAGNETIC EFFECT OF AN ELECTRIC CURRENT depend, to compare, to consist, to contrib­ute, to be interested, to be familiar, to point, to look, to start, to speak

VIII. Answer the following questions.

1. When was the voltaic cell invented? 2. What did Oersted decide to establish? 3. What did he find out? 4. When did the needle deflect MAGNETIC EFFECT OF AN ELECTRIC CURRENT? 5. Who repeated Oersted's experiments? 6. Do you know Ampere's rule? 7. What did Ampere establish and prove? 8. When is magnetism greatly increased? 9. Is the magnetic effect produced when the charges are at rest? 10. What is an electromagnet? 11. When does the iron core act as a magnet?

IX. Compare:

1. Potential energy MAGNETIC EFFECT OF AN ELECTRIC CURRENT and kinetic energy. 2. A series cir­cuit and a parallel circuit. 3. A conductor and an insulator. 4. The magnetic effect of an electric current and the heat­ing effect of an electric current.

X. Make up the annotation of the text and retell it.

LESSON EIGHTEEN

Read and translate the text.

GENERATORS

The dynamo MAGNETIC EFFECT OF AN ELECTRIC CURRENT invented by Faraday in 1831 is certainly a primitive apparatus compared with the powerful, highly efficient generators and alternators that are in use today. Nevertheless, these machines operate on the same principle as the one invented by the great English scientist. When asked what use his new MAGNETIC EFFECT OF AN ELECTRIC CURRENT invention had, Faraday asked in his turn: "What is the use of a new-born child?" As a matter of fact, "the new-born child" soon became an irreplaceable device we cannot do without.

Although used to operate certain devices requiring small currents for their operation, batteries and cells MAGNETIC EFFECT OF AN ELECTRIC CURRENT are unlikely to supply light, heat and power on a large scale. Indeed, we need electricity to light up millions of lamps, to run trains, to lift things, and to drive the machines. Batter­ies could not supply electricity enough to do all this work.

That dynamo-electric machines are used MAGNETIC EFFECT OF AN ELECTRIC CURRENT for this pur­pose is a well-known fact. These are the machines by means of which mechanical energy is turned directly into electrical energy with a loss of only a few per cent. It is calculated that they produce more than 99, 99 per cent of all the world’s electric MAGNETIC EFFECT OF AN ELECTRIC CURRENT power.

There are two types of dynamos, namely, the generator and the alternator. The former supplies d.c. which is similar to the current from a battery and the latter as its name implies provides a.с.

To generate electricity both of them must be continuous­ly provided MAGNETIC EFFECT OF AN ELECTRIC CURRENT with energy from some outside source of me­chanical energy such as steam engines, steam turbines or water turbines, for example.

Both generators and alternators consist of the following principal parts: an armature and an electromagnet. The electromagnet of a d.c. generator is usually called a MAGNETIC EFFECT OF AN ELECTRIC CURRENT stator for it is in a static condition while the armature (the rotor) is rotating. An elementary d.c. generator consists of the armature, the electromagnet, the shunt winding, the commutator and the load. Alternators may be divided into two types: 1. alternators that have a stationary armature and a MAGNETIC EFFECT OF AN ELECTRIC CURRENT rotating electromag­net; 2. alternator whose ar­mature serves as a rotor but this is seldom done. In order to get a strong e.m.f., the ro­tors in large machines rotate at a speed of thousands of rev­olutions per minute (r.p.m.). The faster they rotate MAGNETIC EFFECT OF AN ELECTRIC CURRENT, the greater the output voltage the machine will produce.

In order to produce electricity under the most economical conditions, the generators must be as large as possible. In addition to it, they should be kept as fully loaded as possible all the time. It is interesting to note here MAGNETIC EFFECT OF AN ELECTRIC CURRENT that the biggest generators ever installed at any hydroelectric sta­tion in the world are those installed in Russia: the Bratskaya hydroelectric station is equipped with 225,000 kilowatt (kW) generators. Russian scientists constructed more powerful generators which are installed at the Krasnoyarskaya station. Our industry pro­duces even greater power MAGNETIC EFFECT OF AN ELECTRIC CURRENT installations of 1,200 MW for the steam power plants which play such an important part in the electrification of our country.

Exercises

I. Learn the following words, groups of words. Translate the sentences.

1. armature —якорь. The armature is a part of a gener­ator.

2. to calculate — рассчитывать, вычислять. If you know MAGNETIC EFFECT OF AN ELECTRIC CURRENT Ohm's law you can calculate the circuit.

3. compared with — по сопоставлению с. A ton of ura­nium can give much more energy compared with a ton of coal.

4. to equip— оборудовать. Our laboratory is equipped with reliable instruments.

5.to install— устанавливать, монтировать. A new powerful generator was installed at the power MAGNETIC EFFECT OF AN ELECTRIC CURRENT plant.

6. to operate — работать, действовать. A transformer operates on the principle of electromagnetic induction.

7. rated capacity — номинальная мощность. This power plant has reached its rated capacity.

8. revolutions per minute — об/мин. How many revolutions per minute does this steam turbine make?

9. to rotate — крутить(ся). Water MAGNETIC EFFECT OF AN ELECTRIC CURRENT rotates the turbines at the hydropower stations.

10. scale — масштаб; шкала. Measuring instruments are produced on a large scale in Russia. The Centigrade scale is not used in Great Britain.

11. speed — скорость. Gas turbines rotate with great speed.

12. stationary — недвижный, стационарный. No cur­rent is generated while the magnet is stationary.

13. the MAGNETIC EFFECT OF AN ELECTRIC CURRENT former — 1-ый из упомянутых; the latter— последний из упомянутых. There are two kinds of current: a.с. and d. с. The former changes its direction, the latter does not.

14. steam power plant— термическая электрическая станция. Steam power plants operate on gas and coal.

15. winding— обмотка. Faraday's coil consisted of MAGNETIC EFFECT OF AN ELECTRIC CURRENT eight windings of copper wire.

II. Learn to recognize the following international words.

solenoid, shunt, electrification, dynamo, primitive, rotor, kilowatt, electromagnet, apparatus, industry, plan, elementary

III. Translate the following groups of words.

compared with the results, to install the turbine, to equip with reliable installations, stationary equipment, rotor windings, 5,000 revolutions MAGNETIC EFFECT OF AN ELECTRIC CURRENT per minute

наращивать скорость, номинальная мощность мо­тора, термическая электрическая станция, 1-ый из упомяну­тых, последний из упомянутых, в большенном масштабе

IV. Read the following abbreviations and give their full forms.

i.e., a.c., d.c., r.p.m., e.m.f., m.m.f., 317°F, 45°C, etc MAGNETIC EFFECT OF AN ELECTRIC CURRENT.

V.Translate the following sentences.

1. There is a great number of engineering problems the Russian scientists work at. 2. It is quite impossible to name a scientific problem M.V. Lomonosov did not turn his attention to. 3. There are many electric appliances we cannot do without. 4. The experiment I told you about MAGNETIC EFFECT OF AN ELECTRIC CURRENT will take much time. 5. The direction the needle points in changed several times. 6. The speed a given molecule travels with is greatly increased when a gas is heated.

VI. Form adjectives using the suffixes -able, -full, -less, -ous.

control, continue, danger, value, replace, need, power, peace, use, life MAGNETIC EFFECT OF AN ELECTRIC CURRENT, change, desire, vary

VII. Form adverbs using the suffix -ly and translate them.

exact, electrical, general, gradual, negative, natural, opposite, previous, usual, easy, hard, late

VIII. Translate the following sentences paying attention to the construc­tion the former ... the latter.

1. There are two kinds of current: a.с. and d.c. The MAGNETIC EFFECT OF AN ELECTRIC CURRENT formerchanges its direction, the latterdoes not. 2. I have two friends, Nick and Pete. The formerstudies at the uni­versity, the latterworks at the factory. 3. He has a book on electrical engineering and a book on nuclear physics. The formeris in Russian and the latteris in English. 4. I spoke MAGNETIC EFFECT OF AN ELECTRIC CURRENT to professors G. and W.The formerdelivers lec­tures on chemistry, the latteron semiconductors.

IX. Answer the following questions.

1. When did Faraday invent the dynamo? 2. Was Fara­day an American scientist? 3. Can batteries supply power on a large scale? 4. What do we need electricity for? 5. What are dynamo electric machines MAGNETIC EFFECT OF AN ELECTRIC CURRENT used for? 6. What types of dynamos do you know? 7. What are the principal parts of a generator? 8. In what condition is the stator of an electromagnet? 9. What generators is the Bratsk hydro­electric station equipped with? 10. What is their rated capacity? 11. What are the largest steam power MAGNETIC EFFECT OF AN ELECTRIC CURRENT plants in Europe?

X. Ask your group-mate the following questions. Let him/her answer them.

1. if batteries can supply light, heat and power on a large scale. 2. if the electromagnet is a temporary magnet provided by electricity. 3. if the electromagnet is lifeless unless the electric current flows through the MAGNETIC EFFECT OF AN ELECTRIC CURRENT coil. 4. if the iron core will act as a magnet as long as the current continues to pass along the winding. 5. if the alternator provides a.с. 6. if the generator must be turned by some outside source of mechanical energy.

XI. Make up the annotation of the MAGNETIC EFFECT OF AN ELECTRIC CURRENT text and retell it.

LESSON NINETEEN

Read and translate the text

POWER TRANSMISSION

They say that about a hundred years ago, power was never carried far away from its source. Later on the range of transmission was expanded to a few miles. And now, in a comparatively short period of time, electrical engineering has MAGNETIC EFFECT OF AN ELECTRIC CURRENT achieved so much that it is quite possible, at will, to convert mechanical energy into electrical energy and transmit the latter over hundreds of kilometers and more in any direction required. Then in a suitable locality the electric energy can be reconverted into mechanical energy whenever it is MAGNETIC EFFECT OF AN ELECTRIC CURRENT desirable. It is not difficult to understand that the above process has been мейд possible owing to generators, transformers and motors as well as to other necessary elec­trical equipment. In this connection one cannot mention the growth of electric power generation in this country. The longest transmission line in MAGNETIC EFFECT OF AN ELECTRIC CURRENT pre-Revolutionary Russia was that connecting the Klasson power station with Mos­cow. It is said to have been 70 km long, while the present Volgograd—Moscow high-tension (the English terms "high-tension" and "high-voltage" are interchangeable) transmission line is over 1,000 kilometers long. Generally speaking, the length of MAGNETIC EFFECT OF AN ELECTRIC CURRENT high-tension transmission lines in Russia is so great that they could circle the globe six times, if not more.

It goes without saying that as soon as the electric ener­gy is produced at the power station, it is to be transmitted over wires to the substation MAGNETIC EFFECT OF AN ELECTRIC CURRENT and then to the consumer. How­ever, the longer the wire, the greater is its resistance to current flow. On the other хэнд, the higher the offered re­sistance, the greater are the heating losses in electric wires. One can reduce these undesirable losses in two ways, namely, one MAGNETIC EFFECT OF AN ELECTRIC CURRENT can reduce either the resistance or the current. It is easy for us to see how we can reduce resistance: it is necessary to make use of a better conducting material and as thick wires as possible. However, such wires are calculat­ed to require too much material and, hence, they MAGNETIC EFFECT OF AN ELECTRIC CURRENT will be too expensive. Can the current be reduced? Yes, it is quite possible to reduce the current in the transmission system by employing transformers. In effect, the waste of useful ener­gy has been greatly decreased due to high-voltage lines. It is well known that high MAGNETIC EFFECT OF AN ELECTRIC CURRENT voltage means low current, low current in its turn results in reduced heating losses in elec­trical wires. It is dangerous, however, to use power at very high voltages for anything but transmission and distribu­tion. For that reason, the voltage is always reduced again before the power MAGNETIC EFFECT OF AN ELECTRIC CURRENT is мейд use of.

Lasers.Russian scientists are successfully developing quantum generators, called lasers, for emitting light ampli­tude radio waves. Theoretical calculations have shown that lasers are very likely to transform the energy of light radio waves into electrical energy with an efficiency amounting to about 100 per cent. It MAGNETIC EFFECT OF AN ELECTRIC CURRENT means that electrical power might be transmitted over considerable distances with negligible losses and what is very important without the use of trans­mission lines.

Exercises

I. Learn the following words, groups of words. Translate the sentences.

1. to amount to — доходить до. The electric power gen­eration in MAGNETIC EFFECT OF AN ELECTRIC CURRENT Russia amounted to a great figure.

2. at will — по желанию. The temperature in this room can be regulated at will.

3. considerable — значимый. We pay considerable attention lo the construction of steam power stations.

4. distribution — рассредотачивание. Power distribution is indicated by a straight line in this figure.

5. to emit — источать, выделять MAGNETIC EFFECT OF AN ELECTRIC CURRENT, испускать. A hot body emits heat.

6. equipment— оборудование. This equipment is re­liable in operation.

7. expensive — дорогой. Nuclear fuel is more expensive than mineral fuel.

8. growth — рост, повышение. The growth of cities requires the increase of power generation.

9. range— спектр. This measuring instrument has a wide temperature range.

10. to reduce MAGNETIC EFFECT OF AN ELECTRIC CURRENT — понижать, уменьшать. High voltage is usually reduced at distribution substations.

11. to result in — приводить к; заканчиваться. The sci­entist's work resulted in a great discovery.

12. successfully — удачно. Our industry successfully de­velops powerful reactors.

13. transmission — передача. Underground cables are used for power transmission in large cities.

14. tension — напряжение. High MAGNETIC EFFECT OF AN ELECTRIC CURRENT-tension transmission lines cross our country from East to West.

15. wave — волна. A.S. Popov experimented with electromag­netic waves.

II. Translate the following groups of words.

considerable success, to emit electrons, load distribu­tion, to reduce power losses, to result in great achievements, growth of population, straight MAGNETIC EFFECT OF AN ELECTRIC CURRENT line

драгоценное оборудование, передача электроэнергии, зна­чительное расстояние, источать тепло, рассредотачивание времени

III. Give all the meanings of the following words consulting a dictiona­ry:

scale, generation, armature, revolution, commutator, amplitude, iron, needle, second

IV. Complete the following sentences.

1. Owing to the transformer it became possible ... . 2. It was Ampere who ... . 3. The dynamo MAGNETIC EFFECT OF AN ELECTRIC CURRENT-electric machines are used for ... . 4. In order to reduce resistance in a wire, it is necessary ... . 5. The waste of useful energy can be decreased … . 6. Coal is burned in order to ... . 7. Lasers are used for ... .

V. Translate the following sentences.

1. Чем посильнее магнитное поле, тем больше ток. 2. Чем больше MAGNETIC EFFECT OF AN ELECTRIC CURRENT ток, текущий по проводнику, тем выше температура проводника. 3. Чем меньше труба, тем мень­ше воды проходит через нее. 4. Чем больше скорость движения меж магнитным полем и проводниками, тем больше ток. 5. Чем короче проводник, тем меньше сопротивление проходящему току.

VI. For the terms given in (a) find the Russian equivalents in MAGNETIC EFFECT OF AN ELECTRIC CURRENT (b).

a) 1. power plant; 2. power supply; 3. power generation; 4. power source; 5. power transmission; 6. power unit; 7. power installation; 8. power substation; 9. power trans­former; 10. power factor; 11. power engineering; 12. power capacity; 13. power distribution; 14. power loss

b) 1. выработка электроэнергии; 2. энергопотеря;

3. электроподстанция; 4. силовой трансформатор; 5. ко­эффициент мощности; 6. производительность; 7. источ­ник энергии; 8. рассредотачивание энергии; 9. электростан­ция; 10. передача электроэнергии MAGNETIC EFFECT OF AN ELECTRIC CURRENT; 11. силовая установ­ка; 12. источник питания; 13. энергетика; 14. энергоблок

VII. a) Choose the right term; b) explain the statements.

1. The coil of wire that rotates in a dynamo or a motor is known as:

a) a turbine, b) a stator, c) an armature, d) a generator.

2. Running water is an MAGNETIC EFFECT OF AN ELECTRIC CURRENT illustration of: a) potential energy, b) kinetic energy, c) electric energy, d) heat energy.

3. Steam generators produce electrical energy from: a) potential energy, b) chemical energy, c) light energy, d) mechanical energy.

VIII.Answer the following questions.

1. What мейд it possible to transmit electric energy over hundreds of kilometers? 2. Can MAGNETIC EFFECT OF AN ELECTRIC CURRENT electric energy be reconverted into mechanical energy? 3. What are transform­ers used for? 4. What do you know about the longest trans­mission line in pre-revolutionary Russia? 5. How long is the Volgograd—Moscow high-tension transmission line? 6. In what way can the heating losses be reduced in trans­mission MAGNETIC EFFECT OF AN ELECTRIC CURRENT lines? 7. How can resistance be reduced in elec­tric wires? 8. Why are high-voltage lines used for power transmission? 9. Is it possible to use quantum generators for power transmission? 10. What have theoretical calcula­tions shown?

IX. Make up the annotation of the text and retell it.

LESSON MAGNETIC EFFECT OF AN ELECTRIC CURRENT TWENTY

Read and translate the text

TRANSFORMERS

The transformer is a device for changing the electric current from one voltage to another. As a matter of fact, it is used for increasing or decreasing voltage. A simple transformer is a kind of induction coil. It is well known that in its usual form it has MAGNETIC EFFECT OF AN ELECTRIC CURRENT no moving parts. On the whole, it requires very little maintenance if it is not mis­used and is not damaged by lightning.

We may say that the principal parts of a transformer are two windings, that is coils, and an iron core. They call the coil MAGNETIC EFFECT OF AN ELECTRIC CURRENT which is supplied with current the "primary winding", or just "primary" for short. The winding from which they take the current is referred to as the "secondary winding" or "secondary" for short. It is not new to you that the form­er is connected to the source of supply, the MAGNETIC EFFECT OF AN ELECTRIC CURRENT latter being connected to the load.

When the number of turns of wire on the secondary is the same as the number on the primary, the secondary vol­tage is the same as the primary, and we get what is called a "one-to-one" transformer. In MAGNETIC EFFECT OF AN ELECTRIC CURRENT case, however, the number of turns on the secondary winding is greater than those on the primary, the output voltage is larger than the input voltage and the transformer is called a step-up transformer. On the other хэнд, the secondary turns being fewer in number than the primary, the transformer is MAGNETIC EFFECT OF AN ELECTRIC CURRENT known as a step-down transformer.

The transformer operates equally well to increase the voltage and to reduce it. By the way, the above process needs a negligible quantity of power. It is important to point out that the device under consideration will not work on MAGNETIC EFFECT OF AN ELECTRIC CURRENT d.c. but it is rather often employed in direct-current circuits.

The transformers are used in stepping up the voltages for distribution or transmission over long distances and then in stepping these voltages down. For example, three large step-up transformers are used to increase the potential to 275,000 volts for MAGNETIC EFFECT OF AN ELECTRIC CURRENT transmission over long-distance transmission lines. At the consumer's end of the line, in some distant locality, three step-down transformers are мейд use of to reduce that value (i.e., 275,000 volts) to 2,300 volts. Local trans­formers, in their turn, are expected to decrease the 2,300 volts to MAGNETIC EFFECT OF AN ELECTRIC CURRENT lower voltages, suitable for use with small motors and lamps. One could have some other transformers in the systems that reduce the voltage even further. All radio sets and all television sets are known to use two or more kinds of transformers. These are familiar examples showing that electronic MAGNETIC EFFECT OF AN ELECTRIC CURRENT equipment cannot do without transformers. The facts you have been given above illustrate the wide use of transformers and their great importance.

Exercises

I. Learn the following words, groups of words. Translate the sentences.

1. consumer — потребитель. Power transmission system connects the power station to the consumer.

2. to damage — разрушать, повреждать MAGNETIC EFFECT OF AN ELECTRIC CURRENT. The nearest power station was damaged.

3. induction coil— индукционная катушка. Theinduc­tion coil is connected to the circuit in order to increase its inductance.

4. input— вход; подводимая мощность; входной. The input power of this substation is limited.

5. local— местный. The voltage is reduced at local sub­stations.

6. maintenance— техническое сервис MAGNETIC EFFECT OF AN ELECTRIC CURRENT, уход. The maintenance of this new equipment is expensive.

7. number— число; номер. The number of nuclear power plants has increased in this country. What is the num­ber of your telephone?

8. output— выходная мощность; выходной. The sci­entists try to increase the output power of the genera­tors.

9. to point MAGNETIC EFFECT OF AN ELECTRIC CURRENT out— указывать. The achievements of Russia in power engineering were pointed out in my report.

10.primary— первичный; первичная обмотка трансфор­матора; secondary — вторичный, вторичная обмотка трансформатора. A simple transformer has aprima­ry and a secondary winding.

11. source of supply— источник питания. A battery is a source of supply MAGNETIC EFFECT OF AN ELECTRIC CURRENT.

12.to step down— понижать. What device is used to step down the voltage?

13. to step up— увеличивать. A transformer is used to step up and down the voltage.

14.value— величина. Let us compare these two given values.

15. whole— целый, весь. The students have translated thewhole article.

II. Learn MAGNETIC EFFECT OF AN ELECTRIC CURRENT to recognize the following international words.

globe, laser, quantum, theoretical, induction, electron­ic, plastics, asbestos, volt

III. Translate the following groups of words.

to damage by lightning, secondary distribution line, the number of windings, to step up the current, source ofsupply, the whole world

индукционная катушка, число потребителей, пони­жать MAGNETIC EFFECT OF AN ELECTRIC CURRENT напряжение, вся страна, местные фабрики, пер­вичная обмотка

IV. Form as many words as possible using suffixes and prefixes. De­fine the parts of speech of the new words and translate them.

engine, apply, differ, electric, value, oppose, transform, magnet, conduct, neglect

V.Translate the following sentences.

1. Молвят, что этот прибор описан MAGNETIC EFFECT OF AN ELECTRIC CURRENT в предшествующей статье. 2. Считали, что ток течет от положительного потенциала к отрицательному. 3. Молвят, что мой друг — неплохой математик. 4. Понятно, что М.В. Ломоно­сов основал Столичный институт. 5. Кажется, что это вещество имеет некие другие характеристики. 6. Из­вестно, что переменный ток меняет свое направление.

VI. Form nouns from thefollowing words using MAGNETIC EFFECT OF AN ELECTRIC CURRENT suitable suffixes.

construct, develop, consider, distribute, deflect, equip, connect, require, produce, state, suit

VII.For the word combinations given in (a) find the Russian equiva­lents in (b).

a) 1. a number of; 2. as a matter of fact; 3. on the basis of; 4. for this reason; 5. it goes without saying; 6. at MAGNETIC EFFECT OF AN ELECTRIC CURRENT last; 7. on the whole; 8. to step up; 9. to increase current; 10. to offer resistance; 11. electrical engineering; 12. to step down

b) 1. в конце концов; 2. увеличивать (напряжение); 3. оказы­вать сопротивление; 4. понижать (напряжение); 5. ряд; 6. прирастить ток; 7. на базе чего-л.; 8. по этой при­чине; 9. в целом; 10. электротехника; 11. по сути; 12. разумеется

VIII. Translate the following MAGNETIC EFFECT OF AN ELECTRIC CURRENT sentences and define the functions of the word but.

1. The Fahrenheit scale is mainly used in English speaking countries but it is not used in Russia. 2. His scientific activity lasted but twenty years, but in these twenty years he did very much. 3. Motors are widely em­ployed not only MAGNETIC EFFECT OF AN ELECTRIC CURRENT in industry but also in everyday life. 4. There is but one measuring scale in the instrument. 5. Every­one took an examination in physics but Novikov. 6. A simple transformer is but a kind of induction coil.

IX. Arrange the following words in the pairs of synonyms.

a) 1. amount; 2. big; 3. matter; 4. application; 5. at MAGNETIC EFFECT OF AN ELECTRIC CURRENT present; 6. tube; 7. research; 8. to step down; 9. appliance; 10. minute; 11. arrow

b) 1. investigation; 2. device; 3. needle; 4. quantity; 5. substance; 6. to lower; 7. small; 8. large; 9. new; 10. use; 11. pipe

X.Arrange the following words in the pairs of antonyms.

a) 1. left; 2. increase; 3. beginning; 4. d.c.; 5. above; 6. step-up; 7. at rest; 8. high; 9. short; 10. more

b) 1. end; 2. low; 3. long; 4. step-down; 5. in MAGNETIC EFFECT OF AN ELECTRIC CURRENT motion; 6. less; 7. decrease; 8. below; 9. a.c.; 10. right

XI.Answer the following questions.

1. What is a transformer? 2. What is a transformer used for? 3. Are there any moving parts in a transformer? 4. Can a transformer be damaged by lightning? 5. What are the principal parts of a transformer? 6. How many windings are MAGNETIC EFFECT OF AN ELECTRIC CURRENT there in a transformer? 7. What winding is connected to a load? 8. What is the purpose of a step-up transformer? 9. What is known as a step-down transformer? 10. Does a transformer work on d.c.? 11. In what circuits is the trans­former used? 12. For what purpose are step-down MAGNETIC EFFECT OF AN ELECTRIC CURRENT transform­ers used? 13. Is your radio set equipped with a transform­er? 14. Can we do without transformers? 15. Are transform­ers used both in industry and in our homes?

XII. Compare:

1. A solenoid and an electromagnet. 2. A direct current and an alternating current. 3. A step-up transformer and a MAGNETIC EFFECT OF AN ELECTRIC CURRENT step-down transformer. 4. A stator and a rotor. 5. A primary winding and a secondary winding.

XIII. Make up the annotation of the text and retell it.

ЧЕЛЯБИНСКИЙ Муниципальный АГРОИНЖЕНЕРНЫЙ Институт

МЕТОДИЧЕСКИЕ УКАЗАНИЯ

по британскому языку

для развития способностей работы со спецтекстами

для студентов I и II курсов

по специальностям ЭАСХП и Электроснабжение

Челябинск

Составитель Халупо О.И.


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