Conductors and insulators перевод текста

Conductors and insulators перевод текста

All substances have some ability of conducting the elec­tric current. However, they differ greatly in the ease with which the current can pass through them. Metals, for exam­ple, conduct electricity with ease while rubber does not allow it to flow freely. Thus, we have conductors and insu­lators.

What do the terms "conductors" and "insulators" mean?

Substances through which electricity is easily transmitted are called conductors. Any material that strongly resists the electric current flow is known as an insulator.

Let us first turn our attention to conductance that is the conductor’s ability of passing electric charges. The four factors conductance depends on are: the size of the wire used, its length and temperature as well as the kind of material to be employed.

It is not difficult to understand that a large water pipe can pass more water than a small one. In the same manner, a large conductor will carry the current more readily than a thinner one.

It is quite understandable too that to flow through a short conductor is certainly easier for the current than through a long one in spite of their being made of similar material. Hence, the longer the wire, the greater is its opposition, that is resistance, to the passage of current.

As mentioned above, there is a great difference in the conducting ability of various substances. For example, almost all metals are good electric current conductors. Nevertheless, copper carries the current more freely than iron and silver, in its turn, is a better conductor than copper.

Generally speaking, copper is the most widely used con­ductor. That is why the electrically operated devices in your home are connected to the wall socket by copper wires. Indeed, if you are reading this book by an electric lamp light and somebody pulls the metal wire out of the socket, the light will go out at once. The electricity has not been turned off but it has no path to travel from the socket to your electric lamp. The flowing electrons cannot travel through space and get into an electrically operated device when the circuit is broken. If we use a piece of string in­stead of a metal wire, we shall also find that the current stops flowing.

A material like string which resists the flow of the elec­tric current is called an insulator.

There are many kinds of insulation used to cover the wires. The kind used depends upon the purposes the wire or cord is meant for. The insulating materials we generally use to cover the wires are rubber, asbestos, glass, plastics and others.

Rubber covered with cotton, or rubber alone is the in­sulating material usually used to cover desk lamp cords and radio cords.

Glass is the insulator to be often seen on the poles that carry the telephone wires in city streets. Glass insulator strings are usually suspended from the towers of high voltage transmission lines. One of the most important insulators of all, however, is air. That is why power transmis­sion line wires are bare wires depending on air to keep the current from leaking off.

Conducting materials are by no means the only materi­als to play an important part in electrical engineering. There must certainly be a conductor that is a path, along which electricity is to travel and there must be insulators keeping it from leaking off the conductor.

Exercises

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

1. air— воздух. Air is a poor conductor of electricity.

2. bare wire— оголенный провод. A bare wire is a wire not covered with insulating material.

3. cord — шнур. A cord is a small insulated cable.

4. to cover — покрывать. The train covers a great dis­tance from Moscow to Vladivostok.

5. electrical engineering — электротехника. We study electrical engineering.

6. glass— стекло; стакан. Glass is a good insulator. We need glasses for a chemical experiment.

7. insulation— изоляция. If a wire is covered with in­sulation it is called an insulated wire.

8. to leak off— утекать. If there is no insulation the current can leak off the conductor.

9. opposition— противодействие, сопротивление. When the temperature risesopposition to the passing current increases.

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10. pole— полюс; столб, опора. Any magnet has two poles. What are the poles of a transmission line made of?

11. to resist — сопротивляться, противодействовать. We shall consider the ability of insulators to resist the current flow.

12. rubber— резина. Rubber is a perfect insulator.

13.similar— одинаковый, похожий, однородный. Some liquids have similar properties.

14.socket— розетка, патрон (электролампы). Copper wires connect electrical devices to the socket.

15. to turn off— выключать. If the switch is turned off’ the current does not flow.

16. to transmit— передавать (электроэнергию); посы­лать. Electricity is transmitted by wires.

II. Translate the following groups of words.

air insulator, similar conditions, to cover, the wires, electrical engineering, wall socket, North pole

выключать свет, стеклянные изоляторы, оголенный провод, передавать электрический ток, покрытый ре­зиной, высокий столб

III. Complete sentences according to the model given below.

Model: The method used . . → The method used is described in the present article. Исполь­зуемый метод описан в данной статье.

1. The device tested . . 2. The results obtained . . 3. The temperature measured . . 4. The phenomenon studied . . 5. The conductors used . . 6. The substance mentioned . . 7. The method proposed . .

IV. Translate the following groups of words.

research work—research work plan; water pipe—water pipe material—water pipe material quality; power supply— power supply increase—power supply increase problem; transmission line—transmission line wire—transmission line wire insulation; space investigation—space investiga­tion program—space investigation program discussion

V. For the words given in (a) find the Russian equivalents in (b).

a) 1. wire; 2. statement; 3. to cause; 4. collision; 5. to control; 6. feature; 7. similar; 8. direction; 9. opposition; 10. positive; 11. path; 12. to consider; 13. as well; 14. to expect; 15. to place

b) 1. положительный; 2. также, тоже; 3. считать, рас­сматривать; 4. направление; 5. ожидать, рассчитывать; 6. помещать; 7. путь, контур; 8. противодействие; 9. особенность; 10. подобный; 11. столкновение; 12. уп­равлять; 13. утверждение; 14. вызывать, заставлять; 15. проволока

VI. Answer the following questions.

1. What is discussed in the present article? 2. Do all substances conduct the electric current easily? 3. What is a conductor? 4. What does conductance depend upon? 5. What materials are the best conductors of electricity? 6. Does temperature influence the conductor’s resistance? 7. What is the difference between a conductor and an insu­lator? 8. What insulators do you know? 9. Why are power transmission line wires bare? 10. What insulation is used on the cords of your electrical devices? 11. Can we do with­out insulators?

VII. Explain why:

1. we need conductors and insulators. 2. we compare water flow and current flow. 3. we mostly use copper conductors. 4. the current flows when you turn on the light. 5. lightning strikes the nearest conductor. 6. there must be a difference of potential in the circuit.

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

Из за большого объема этот материал размещен на нескольких страницах:
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Основными частями конденсатора являются металлические пластины и изоляторы. Изоляторы нужны, чтобы изолировать металлические пластины и, таким образом, предотвращать короткое замыкание.

Есть два основных типа конденсаторов, используемых в настоящее время: постоянный и переменный. Пластины постоянного конденсатора неподвижны, поэтому его ёмкость не меняется. Пластины переменного конденсатора подвижны, и его ёмкость меняется. Чем больше расстояние между пластинами, тем меньше ёмкость конденсатора. Переменные конденсаторы обычно используются радистами; их функция – менять частоту в цепи. Постоянные конденсаторы используются в телефонии и радиоделе.

В постоянных конденсаторах изоляторы сделаны из бумаги, керамики и других материалов; у переменных конденсаторов воздушные изоляторы. Бумажные конденсаторы обычно используются в радиотехнике и электронике; их преимуществом является высокая ёмкость: она может быть выше, чем 1000 пикофарад.

Кроме того, широко применяются электролитные конденсаторы. Они также имеют очень высокую ёмкость: она варьируется от 0,5 до 2000 микрофарад. Их недостатком является то, что они меняют свою ёмкость при изменении температуры. Они могут работать без изменения только при температурах не ниже, чем -40 С.

Неисправностями конденсатора являются разрыв и короткое замыкание. Конденсатор перестает работать и не накапливает энергию в случае неисправности. Неисправный конденсатор надо заменить новым.

Find the correct variant. Remember it:

1. a capacitor is used

a) to supply voltage

b) to increase the voltage output

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c) to store energy

2. the main parts of a capacitor are

a) insulators only

b) metal plates only

c) metal plates and insulators between them

3. the function of insulators is

a) to store energy

b) to isolate the metal plates

c) to prevent a short between the metal plates

4. the capacity of a capacitor depends on

a) the size of the plates

b) the distance between the plates

c) the material of the insulators

5. the capacity of a fixed capacitor

6. the plates of a variable capacitor

b) cannot be moved

7. in order to charge a capacitor a voltage source is applied

a) to the metal plates

b) to the insulators

8. the greater the distance between the plates

a) the greater the capacity of a capacitor

b) the less the capacity

9. variable capacitors have

a) air insulators

b) paper insulators

c) ceramic insulators

electrolyte capacitors have

a) a very low capacity

b) a very high capacity

11. in case a capacitor has a trouble

b) it stops operating

Finish the sentences using the words with the opposite meaning:

I. The plates of a fixed capacitor cannot be moved to vary the capacity… … . 2. The capacity of a variable capacitor is varied. 3. Electrolyte capacitors change their capacity when the temperature changes. … . 4. The less the distance between the plates the greater the capacity . . . 5. \’hen a capacitor has no trouble it stores energy … … .

Answer the following questions:

I. What is a capacitor used for? 2. What are the main parts of a capacitor? 3. What is the function of insulators? 4. What does the capacity of a capacitor depend on? 5. What is the difference between a fixed capacitor and a variable one? 6. What should be done in order to change a capacitor? 7. What is the relation between the value of capacity and the distance of plates? 8. What type of insulators have variable capacitors? 9. What should be done in case a capacitor has a trouble?

Ответы и решения

2 — с; 3 — b, с; 4 — b; 5 — a; 6 — a; 7 — a; 8 — b; 9 — a; 10 — b; 11 — Jb.

1. variable move

2. fixed does not change

3. paper do not change

4. the greater the less

5. has does not store

1. to store electric energy

2. metal plates and insulators

3. to isolate the metal plates

4. the voltage, the size of plates and their number, the distance between the-plates, material

5. fixed — capacity does not change; variable — changes

6. to change insulator

7. the greater the distance the less the capacity

8. air insulators

9. it should be substituted.

CONDUCTORS AND INSULATORS

copper wire conductors

Conductors are materials having a low resistance, so that current easily passes through them. The lower the resistance of the material the more current can pass through it.

The most common conductors are metals, and silver and copper are the best of them. The advantage of copper is that it is much cheaper than silver. Thus copper is widely used to produce wire conductors. One of the common functions of wire conductors is to connect a voltage source to a load resistance. Since copper wire conductors have a very low resistance a minimum voltage drop is produced in them. Thus, all of the applied voltage can produce current in the load resistance.

It should be taken into consideration that most materials change the value of resistance when their temperature changes.

Metals increase their resistance when the temperature increases while carbon decreases its resistance when the temperature increases. Thus, metals have a positive temperature coefficient оf resistance while carbon has a negative temperature coefficient. The smaller is the temperature coefficient or the less the change of resistance with the change of temperature, the more perfect is the resistance material.

Проводники – это материалы, имеющие низкое сопротивление, так что ток легко проходит через них. Чем ниже сопротивление материала, тем больший ток может проходить через него.

Самые распространенные проводники – металлы, а серебро и медь – лучшие из них. Преимуществом меди является то, что она намного дешевле серебра. Таким образом, медь широко используется для производства проволочных проводников. Одна из основных функций проволочных проводников – соединять источник питания с нагрузочным сопротивлением. Т. к. медные проводники имеют очень низкое сопротивление, в них теряется минимум напряжения. Таким образом, все приложенное напряжение может производить ток в нагрузке.

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Следует принять во внимание, что большинство материалов меняют сопротивление при изменении температуры.

Сопротивление металлов увеличивается при повышении температуры, а сопротивление угля падает. Таким образом, металлы имеют положительный температурный коэффициент сопротивления, а уголь – отрицательный. Чем меньше температурный коэффициент или меньше изменение сопротивления с изменением температуры, тем лучше материал сопротивления.

I. Answer the following questions:

I. What is the text about? 2. What materials are called conductors? 3. What is the advantage of copper compared with silver? 4. What is the most common function of wire conductors? 5. Why is a minimum voltage drop produced in copper conductors? 6. What is the relation between the value of resistance and the temperature in carbon?

Ответы и решения

2. with a low resistance

3. it is much cheaper

4. to connect a voltage source to a load resistance

5. they have a very low resistance

6. carbon decreases its resistance when the temperature increases.

make something do something

Materials having a very high resistance are called insu­lators. Current passes through insulators with great diffi­culty.

The most common insulators are air, paper, rubber, plastics.

Any insulator can conduct current when a high enough voltage is applied to it. Currents of great value must be applied to insulators in order to make them conduct. The higher the resistance of an insulator the greater the applied voltage must be.

When an insulator is connected to a voltage source, it stores electric charge and a potential is produced on the insulator. Thus, insulators have the two main functions:

1. to isolate conducting wires and thus to prevent a short between them and

2. to store electric charge when a voltage source is ap­plied.

Материалы, имеющие очень высокое сопротивление, называются изоляторами. Ток проходит через изоляторы с большим трудом.

Самые распространенные изоляторы – это воздух, бумага, резина, пластики.

Любой изолятор может проводить ток при достаточно высоком приложенном напряжении. Чтобы сделать изоляторы проводниками, к ним должно быть приложено напряжение большой величины. Чем выше сопротивление изолятора, тем большее напряжение должно быть приложено.

Когда изолятор соединен с источником питания, он накапливает электрический заряд и создает потенциал. Таким образом, изоляторы имеют две главные функции:

1. изолировать проводники и, таким образом, предотвращать короткое замыкание между ними и

2. накапливать электрический заряд при наличии источника питания.

Conductors and Insulators
All substances have some ability to transmit electrons but they differ greatly in the ease with which electrons pass through them. For instance, a copper wire conducts electricity readily, glass conducts so little currents that it is hardly measurable. Substances through which currents easily pass are the conductors. Substances strongly resisting the flow of current are the insulators. An insulator is also called a dielectric.
Almost all metals are good conductors of electricity but we consider silver to be the best conductor of all. Copper comes next, it is followed by aluminium. Copper is our commonly used conductor.
Some liquids also conduct electric currents. They even prove to be good conductors of electricity. Most gases conduct current under proper conditions of pressure and temperature. However, they are not as good electrical conductors as metals.
The most common materials used to resist electric flow are: glass, rubber, porcelain, paper, oil, cotton and silk. Non-ionized clean air is also considered to be a good insulator. It is often used for this purpose in electrical apparatus.
It would be quite wrong to think that conducting materials are the only materials used for the transmission of power. We need both conductors and insulators. We cannot do without the copper wire which conducts the electric power and, acts as a conductor. However, we have to use an insulator to prevent electrical losses.
In the transmission of power we generally employ the best conductors.

Пояснения к тексту:
for instance – например
however – однако
it would be quite wrong – было бы неправильно …..
the only – единственный
to do without – обходиться без
in order that – для того, чтобы

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