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Файл:Английский язык для обучающихся по энергетическим специальностям. Учебное пособие.pdf
UNIT 13. THE MAGNETIC EFFECT ON AN ELECTRIC CURRENT
magnetic needle |ˈniːd(ə)l| – магнит-
coil – катушка
right angle |rʌɪt ˈaŋɡ(ə)l| – прямой
to increase |ɪnˈkriːs| – увеличивать
nevertheless |nɛvəðəˈlɛs| – тем не
to suspend |səˈspɛnd| – подвешивать
deflection |dɪˈflɛkʃ(ə)n| – отклонение
temporary |ˈtɛmp(ə)rəri| – временный
to point out – указывать, замечать
behavior |bɪˈheɪvjə| – режим ра-
to adjust |əˈdʒʌst| – регулировать,
as long as – пока
reverse |rɪˈvəːs| – обратный
to attract |əˈtrakt| – притягивать
to depend on – зависеть от
to repel |rɪˈpɛl| – отталкивать
to establish |ɪˈstæblɪʃ| – устанавли-
to detect |dɪˈtɛkt| – обнаружить
to turn one’s attention |əˈtɛnʃ(ə)n| –
source |sɔːs| – источник
Vocabulary
ная стрелка
угол
менее
устанавливать
вать
боты
обращать внимание
The invention of the voltaic cell in 1800 gave electrical experimenters a
source of a constant fl ow of current . Seven years l ater the Danis h scientist and
experimenter, Oersted, decided to establis h the relation between a f low of current and a mag netic needle. It took hi m at least 13 years more to find out th at a
compass needl e is reflected when b rought near wire thr ough which the electri c
current is flowing. Before he made his important discovery, Oersted had tried
many times to pl ace a cu rr ent -car rying wi re at right angles to the magnetic needle, nevertheless he could detect no deflection. At last, duri ng a lecture and in
the presence o f his students, he adjus ted by chance, Then, the wire parallel to
the needle. Then, both he and his class saw that when he current was turned on,
the needle def lected almost at rig ht angles toward the co nductor. When th e direction of the current was reversed, the direction the needle pointed in was reversed too. When the current flowing from left to right, the north end of the
71
needle moves away from us as seen in Fig. 8. Oersted also pointed out that
when the wire was adjus ted belo w the need le, th e directi on was reverse. Hen ce,
the movement o f the needle also depended on th e position of th e wire, above it
or below it.
Fig. 8. Influence of an electric current on a compass needle
The above-mentioned phenomenon highly interested Ampere (Fig. 9). That
the unit of cu rrent is named after the fa mo us French physicist an d mathematician is probably known to everyone.
Ampere heard of Oersted’s achievements and he, in his turn, repeated the
experiment and added a number of further valuable observations and state-
72
ments. His co ntribution t o “electrodyn amics”, as he hims elf called t he new science, began in 1812 under the influence of Oersted’s discovery and continued
throughout the rest of his life. Everyone knows the rule thanks to which we can
always find th e di recti on of th e magnet ic ef fect of a cur ren t. It is kn ow n as Ampere s rule. It was Ampere who established and proved that magnetic effects
could be produced without any magnets, by means of electricity alone. He
turned his attention to the behavi or of electric curren t in a single straig ht conductor and in a c onductor that is formed into a coil.
Fig. 9. Andre Marie Ampere (1775–1836)
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 t he number of turns of wire, the greater will be the m. m. f. (that is
the magneto-motive force) produced within the coil by any constant amount of
current flowing through it. In addition, when doubling the current, we double
the magnetism g enerated in the co il. However, we must not forget that an electric charge at rest does not produce any magnetic effect at all.
A solenoid has two poles which attract and repel the poles of other magnets. While suspended it takes up a north and south direction exactly like the
73
compass needle. A core of iron becomes strongly magn etized if placed within
the solenoid while the current is flowing.
When winding a coil of wire on an iron core, w e obtain what is called an
electromagnet . It is a temporary magn et provid ed by electricity. I ts behavior is
very simple. Th e de vice i s lif eless unless an elect ric cur rent flo ws thr ough a t he
coil. However the device comes to life provided the current flows. The iron
core will act as a magnet as long as the current continues passing along the
winding. One may ask “What advantage does an el ect ro ma gn et p oss ess over an
ordinary magnet since both can attract and repel magnetic materials?” That
electromagn ets are control lable and reliable magnets is perhaps known even to
a schoolboy. They become strong magnets when we want them to. They will
lose their magnetic properties as soon as the current is turned off.
Exercises
1. Translate the following sentences.
1. When placi ng an iron co re within the co il, we greatl y increase t he magnet’s efficiency. 2. If susp ended so th at it can rot ate freely, the solen oid may be
observed o point north and south when the current flows. 3. This circuit can be
closed, if necessary. 4. When placed in a strong magnetic field, iron becomes
magnetized. 5. When speaking about a direct current, we mean a continuous
current.
2. Translate the following sentences and change them according to the
model given below.
Model: It is the sun that is an unlimited source of almost all kinds of energy.
The sun i s an unlimited source of almost all kinds of energy.
1. Ii is in the electrical appliance that the electric energy is changed into
heat. 2. It is the increase in temperature that increases the molecular motion.
3. It was Ampere who showed the difference between the current and the electrical charges. 4. It is at the power station that electricity is produced. 5. This
the magnetic effect of the current that is the subject of this article. 6. It is the
unit of current that is named after Ampere.
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3. Fill in the blanks with where, which, when, who, that.
1. We know … Oersted established the connection between an electric
flow of current and a magnetic needle. 2. The great scientists Volta, Ampere
and Yablochkov may be named among those … have greatly contributed to
electrical eng ineering . 3. The end … the lines of force leave the coil af ter passing through it s core will act like a north magnetic pole. 4. … th ere is a certain
connection between electricity and magnetism was proved by experiments.
5. … he placed the wire parall el to the needle he s aw … the needle defl ected.
6. A wire … is wo und in the for m of a solenoi d acts like a mag net as long as it
is carrying a current.
4. Fill in th e blan ks wi th su ita ble p repo si tion s, ma ke up sent ences w ith
the following infinitives.
To equip …; to depend …; to compare … ; to consist …; to contribute …;
to be interested …; to be familiar … .
5. Form nouns of the following verbs and translate them.
To invent, to connect, to discover, to achieve, to observe, to state, to con-
tribute, to conduct, to produce, to opera t e, to deflect.
6. Compare.
1. Potential energy and kinetic energy.
2. A serious 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.
7. Look at Fig. 8 and desc r ibe Oersted’s discovery.
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UNIT 14. GENERATORS
to rotate |rə(ʊ)ˈteɪt| – вращать(ся)
such as |sʌtʃ| – такой как
more than – больше, чем
to operate |ˈɒpəreɪt| – управлять
to be able to – быть способным
armature |ˈɑːmətʃə| – якорь
although |ɔːlˈðəʊ| – хотя
in order to |ˈɔːdə| – для того, чтобы
cell |sel| – ячейка, батарея
revolutions per minute (r. p. m.)
to be unlikely |ʌnˈlʌɪkli| – маловеро-
voltage |ˈvəʊltɪdʒ| – напряжение
to supply |səˈplʌɪ| – снабжать, по-
to suppose |səˈpəʊz| – предпола-
purpose |ˈpəːpəs| – цель
it goes without saying – само собой
by means of |miːnz| – посредством,
irreplaceable |ɪrɪˈpleɪsəb(ə)l| – неза-
namely |ˈneɪmli| – а именно
to do without |wɪðˈaʊt| – обходить-
Vocabulary
|ˌrevəˈluːʃənz pɜː ˈmɪnɪt| – обороты
в минуту
ятно
ставлять
с помощью
гать
разумеется
менимый
ся без
Great generators in our power stations, which rotate at a constant speed
day and night, summer and winter, are able to gen erate elect ric en ergy o nly b ecause of the el ectromagnets. It i s calculated that these mac hines produce more
than 99.99 percent of all the world’s electric power.
Although used to oper ate certain devices requ iring small currents for thei r
operation, batteri es an d cells ar e un likel y to supply light, heat and power on our
modern large scale. It is dynamo-electric machines that are used for this pur-
pose. These are machines by means of which mechanical energy is turned di-
rectly electric energy with a loss of only a few per cent.
There are two t ypes of dynamos, namely, the alternat or and the generator.
The former provides a. c. while the latter supplies d. c., similar to the current
from a battery. Both of them must be turned by some outside source of mechan-
76
ical energy, such as water p ower, for example. Where cities ar e far from water
power, the mechanical energy fo r the gen erator mostly co me fro m burni ng coal
which operates a steam turbine which turns the generator.
Both generato rs and alternat ors consist of the f ollowing princip al parts: an
armature an d an electromagnet. Th e former generally s erves as a rotor in d. c.
generators while it is the magnetic system that serves this purpose in alternators. The latter is usually called a stator for it is in a static condition. In order to
get a strong e. m. f ., the ro tors in large alt ernat ors ro tate at a sp eed of t hou sand s
of revolutions per minute (r. p. m.). In this connection one could add that the
speed of rotat ion will control th e output voltage of the generator in the following manner:
1. The faster the armature is rotated, the more voltage the generator will
produce.
2. The slower the rotation, the less the output voltage.
Fig. 10. A modern generator
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Electric power stations which sup ply electricity over long distances are at
present always equipped with large alternators. These supply us with much
greater quantities of current than anything ever supposed by Volta, Oers ted and
Ampere.
In order to produce electricity under the most economical conditions, the
generators mus t be as large as possibl e. In additio n to it, they sh ould be kep t as
fully loaded as possible all the time.
Fig. 11. Michael Faraday (1791–1867)
It goes without saying that the dynamo invented by Faraday (Fig. 11)
in 1831 would seem to be a most primitive apparatus compared with the powerful, highly-efficient machines that ar e in use today. Nevertheless these generators and alt ernators work on th e same pri nciple as t he one in vented by the great
English scien tist. When asked what us e his new invention had, Faraday is said
to have asked in his turn: “What is the use of a new-born child?” As a matt er of
fact, the “n ew-born child” soon became an irreplaceable device we cannot do
without.
78
Exercises
1. Translate the following sentences.
1. Heat developed in a transmission line or a generator is a needless waste
of energy. 2. An electric lamp uses the light given off by its filament heated by
the current . 3. The experiments made by Oersted attr acted Ampere’s atten tion.
4. Electric po wer stations supplying power on a large scale are equipped with
large alternators.
2. Translate the following sentences and combine the principal and
subordinate clauses with suitable conjunctions.
1. There is a gr eat number of engineering prob lems the Russian scientists
work at. 2. It quite impossible to name a scientific problem Lomonosov did not
turn his attention to. 3. There are many el ectric appliances we cannot do without. 4. The expe riment I told you about will take much time.
3. Answer the following questions.
1. Do you wan t to tran slate th is arti cle. 2. Do yo u want me to tr anslate th is
article. 3. Do you know th is scientist? 4. Do you know this scientist to have explained the new phenomenon. 5. Did you hear my report? 6. Did you hear my
friend make a rep or t? 7 . Did yo u see my bro th er? 8. Di d you s ee my b ro th er enter the room?
4. Form adjectives using the suffixes -able, -ful, -less, -ous.
Control, conti nue, danger, value, replace, need, power, peace, use, life.
5. Form adverbs using the suffix –ly.
Exact, electrical, general, gradual, negative, natural, opposite, previous,
usual, easy.
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6. Define the following terms.
I
II
rent from the source and back to the
5) is a device by means of which heat
1) electromotive force,
2) electric circuit,
3) heating effect of an electric current,
4) magnetic effect of an electric current,
5) electromagnet,
6) generator.
7. Translate the following sentences.
1. Чем сильнее магнитное поле, тем больше ток. 2. Чем больше ток,
текущий по проводнику, тем выше температура проводника. 3. Чем меньше труба, тем меньше воды проходит через нее. 4. Чем короче проводник,
тем меньше сопротивление проходящему току. 5. Чем больше скорость
движения между магнитным полем и проводниками, тем больше ток.
8. Form sentences combining suitable parts of the sentence given
below.
1) electric circuit
2) e. m. f.
3) heat engine
1) is a temporary magnet provided by
electricity;
2) is an electrical appliance used in
our everyday life;
3) is a path to be followed by the cur-
4) iron
source;
4) is the force that makes electrons
5) electromagnet
9. Look at Fig. 10 and describe it.
move along a conductor;
is turned into work.
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