TEXT 4

1. оставьте2 вопроса покартинке (рис.4) и обсудите ихв группе.

Си бАРис. 4

2. Прочтите текст, разделите его на смысловые части, подберите названия к каждой из них.

DIFFERENCE BETWEEN CONDUCTORSДAND INSULATORS

FROM THE ELECTRON VIEWPOINT

When a conductor is carrying an electric current, the electrons are moving gradually along through the substance of the conductor. Now in a solid body, such as a metalic conductor, the atoms or molecules comprising the substance are known practically to be fixedИin position. They are not actually stationary in space at ordinary temperature, of course; as a matter of fact, the atoms have an irregular to-and fro-motion similar to that of the electrons. But there cannot be a progressive motion of the atoms as there may be of the electrons. The reason for this is more or less evident. Suppose a current to be flowing along a copper wire. The electrons move all the way around the circuit through the wire, connections, solution in the battery, etc.

The atoms of copper being charged positively after an electron has left them, it might seem that as the electrons move from B to A through the wire the atoms would move from A to B, then into and through the battery and so back to the wire. But the atoms are thу real substance of the wire,

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and hence if the atoms should progress one way or the other it would result in the copper itself being carried from one end of the wire to the other and then through the battery. This state of affairs is not possible in solid bodies like metals, it would result in the mixing of metalswherever a current left

one metal and went into another.

Сmolecule are called ions; the metallic ion (in above case, copper) lacks one electronиand so is charged positively. If now a current is passed through such a solution, the metallic ion does move through the solution and is carried from the solution to one of the wires by which the current is led into the solution. Here copper itself is transported by the current and we have the process ofбАelectro-plating.

In chemical solutions, e.g., copper sulphate in water, the salt mole-

cule breaks up into two parts, one of which has one electron more than its proper number, the other part lacking one electron. The two parts of the

Thus, the molecules of a body clinging to the electrons so tightly that none of them are free to move away from the molecule, there can be no current in such a substance. As long as the mplecule keeps all the electrons, it remains electrically neutral, and so has no tendency to move in an electric field. This is the essential difference between insulators and conductors; in one the electrons cannot move from the atom or molecule and in the other the electrons are perfectly free to leave the atom.

connection – связь, присоединениеД;

3. Прочитайте и выучите.

Substance – вещество;

stationary – неподвижный, стационарный, постоянный; irregular – неравномерный, неправильный;

solution – раствор, разрешение (вопроса, проблемы);

sulphate – сульфат, соль серной кислоты; sulphate of copper (of iron, of zinc) медный (железный, цинковый) купорос;

4. Найдите в тексте английские эквиваленты следующих слов:

такой, как; конечно; по сути; взад и вперед; причина этого в том; более или менее приводить к (чему-либо); где бы ни; например; пока; следовательно.

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5. Переведите с русского на английский язык, используя данные выражения:

to some degree (extent), the...the, both...and.

1. Все вещества в твердом или жидком состоянии обладают до некоторой степени электрической проводимостью. 2. Как проводники, Стак и изоляторы имеют очень широкое применение в электротехнике. 3. Чем больше приложенное напряжение, тем ярче свет электриче-

ской лампы.

различные6. Перевед те следующие предложения, обращая внимание на значен я употребление глагола

1. Such an instrument as the moving iron attraction type is suitable for use with both alternating as well as direct currents. 2. It is necessary to take into accountбАthat some instruments have a scale which does not start at zero. 3. One method of detecting the presence of a current in a wire is to measure the rise in temperature of the wire due to theto current.be. 4. Iron, nickel or other magnetizable substances are to be thought of as composed of molecules or groups of molecules each of which is a perfect little magnet with its two opposite magnetic poles. 5. There is always something of the nature of a resistance or opposition which has to be overcome. 6. The armature is at rest, and in the absence of any back e.m.f. the low armature resistance would allow a very heavy current to flow in it.

7. Определите форму и функцииДгерундия и переведите следую-

щие предложения:

1. Before switching on current for a test the circuit should be thoroughly checked over to see that it is in accordance with the circuit diagram, particular care being take that ammeters are not directlyИacross the mains. 2. If the atom should progress one way or the other, it would result in the copper itself being carried from one end of the wire to the other and then through the battery. 3. On joining the upper ends of the metals with a metal wire we caused the current to flow through the wire. 4. The use of a cooling medium prevents the device from overheating. 5. The most common method of magnetizing permanent magnets is to insert the magnets in a suitable exciting coil and to cause a large current to flow in the coil. 6. The new method could be used with great advantage without the machine being overheated. 7. The meter being highly accurate is of the greatest importance for getting the necessary experimental data. 8. We know of silver and copper being very good conductors of electricity. 9. Breaking the circuit causes sparking

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as a result of the coil current flow. 10. Not stopping the machine will prevent too rapid cooling with subsequent freezing of the bearings or warping

2. Прочтите заглавие следующего текста и скажите, о чем, по вашему мнению, будет идти речь в тексте.

SOME FACTS ABOUT THE MAGNETS

Being heated a magnet loses some or all of its magnetism. A magnet being broken in two, each piece becomes a magnet with its own pair of poles. This subdivision could be carried on until we were down to the

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smallest particle of iron, a molecule. Conversely, two identical bar magnets being brought end to end with opposite poles in close contact, the poles touching seem to disappear and we have but two poles at the extreme ends. A tube of iron filings may be magnetizid by stroking it with a magnet in the usual way. The filings being shaken, the magnetism disappears.

СThese facts give rise to the very plausible theory of magnetism gen-

erally accepted. We know iron molecules to be magnets at all times. When they are arranged in a bar oа steel or iron so that the fields of force of all or most of the molecules are in the same direction, their fields are added to one another and the bar is a magnet. The little magnet molecules form chains, their poles disappearing except at the ends of the chain. This condition is not an equilibrium condition because of the like poles in adjacent chains repelling each other. The rigidity of steel holds the molecules in this

и position. InбАsoft iron, however, as soon as we take the bar out of the mag-

netizing field, the molecules adjust themselves on account of the repulsions of like poles of molecules in adjacent chains, leaving the iron unmagnetized. We can see why hard steel makes permanent magnets and soft iron dors not.

We can also explain why soft iron has a higher permeability than steel. When placed in a magnetic field, the molecules of steel do not readily turn around in the direction of the lines of force. But this alignment is necessary if the body is to absorb lines of force. Heating which increases

filing – наполнитель, прокладка; Д plausible – вероятный, правдоподобный, благовидный; equilibrium – равновесие;

molecular motion, or jarring causes a magnet to be demagnetizid due to its permitting the molecules to adjust themselves to the equilibrium position.

adjacent – смежный, примыкающий, соседний; repel – отталкивать;

rigidity – жесткость;

pole – полюс, like (opposite(unlike)) poles – одноименные (разноимен-

ные) полюсы;

alignment – выравнивание, выверка, настройка, регулировка.

4. Составьте цепочку из основных фактов текста, в которой ключевые слова были бы связаны по смыслу.

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5. Изучите следующие синонимичные группы слов и выражений.

Составьте предложения, употребляя данные выражения: conversely, on the contrary; under consideration, in question; at hand, in point; to meet the requirements, to fill the requirements; meet the demands, to fill the demands; thanks to, due to, owing to, because of, on account of, by virtue of.

Сwise, unlike.

6. Найд те в тексте антонимы к следующим словам. Составьте с ними предложен я.

бинацdepending on the area of the surface, whereas fission action takes place throughout the body and is therefore a volume effect. 2. The varying current from the television takes the place of the voice currents from the microphone. 3. The discovery of the atomic battery may take its place alongside with nuclear reactors in providing the world with new sources of electricity.4. Many radio amateurs take advantage of radio transmitters with one vacuum tube only. 5. It would take 100 million of small thimble sized

To appear, different, to attract, hard, low, to decrease, to acquire, up, like-

7. Изуч те употре ление и значение слова take в различных ком-

atomic batterirsбАto produce enough electricity to light a 100-walt bulb, but its discovery is a very important one. 6. In atomic power plants special safety precautions must be taken to protect the workers from the danger of radioactivity. 7. It will take not very much time to see the widespread use

ях. Перевед те следующие предложения:

1. The escape of neutrons from any quantity of uranium is a surface effect

of semiconductors in every-day life. 8. In metals conduction takes place through the motion of electrons.

8. Прочтите текст повторно и ответьте на вопросы.

Д И

1. What happens to a magnet: a) when it is heated or broken in two? b) when two indentical bar magnets are brought end to end with opposite poles in close contact? 2. When does a bar become a magnet? 3. When do the molecules adjust themselves? 4. Why does hard steel make permanent magnets and why has soft iron a higher permeability than steel?

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9. Переведите на английский язык следующий текст:

Нагревание магнита приводит к потере им магнетизма. Если разделить магнит на две части, то каждая из них остается магнитом, т.е. каждая часть будет иметь свою пару полюсов. И наоборот, если соединить два магнита, то в результате получится один большой магнит. Общепринятая теория магнетизма легко объясняет ряд очень интересных явлений. Например, почему твердая сталь обладает постоянными магн тными свойствами, в то время как мягкое железо лишено их. Также на основании этой теории можно объяснить более высокую магн тную прон цаемость мягкого железа по сравнению со ста-

Student: If a piece of iron is placed in the coil, the iron will become magnetized by the electromagnetic field and an electromagnet is produced. Demonstrator: When would the iron be demagnetized?

Student: If the electron flow through the coil ceased, the magnetic field would collapse and the iron would no longer be magnetized. Demonstrator: What can you say about permeability and retentivity in soft iron and steel?

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Student: Well, the soft iron has high permeability and low retentivity, while steel has low permeability and high retentivity.

Demonstrator: -------------------------------------!!!

11. Прочтите и выучите следующие слова: needle – игла, стрелка (прибора);

cease – прекращать (-ся), переставать, приостанавливать; collapse – руш ться, сплющиваться, обваливаться;

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