It is easily seen that in a solenoid there is a complete field around each turn. These fields are somewhat modified by the adjacent turns, there being many straight lines coming out from the sides of the coil. Should the coil be wound on a core of soft iron of high permeability, the core would absorb these straight lines and give a concentrated field from one end of the core to the other. We then have an electromagnet. We use soft iron not only because of its having a high permeability, but because its low retentivity allows very little residual magnetism when the current is turned off. The strength of the magnet increases with the number of amperes flowing and also with the number of turns. The product of amperes and turns is called ampere turns. The strength of an electromagnet with a given core is known to be proportional to the number of ampere turns, the strength of the field depending on the shape of the core. If the poles were brought together into a U shape, the field would become stronger. Of course, the two legs of the U must have opposite poles. The most obvious use of the electromagnet is in lifting iron weights. They are often capable of holding pieces of iron or steel weighing thousands of pounds; they do not slip, as do hooks and ropes; and they can be operated by the throw of a switch at a distance. We know small, powerful electromagnets to be used by doctors to remove steel particles from the eye. Among the common applications of the electromagnet are the electrical bell, the telephone, the telegraph, radio loud-speaker, circuit breakers, relay for remote control of machines, electrical measuring instruments, motors, and generators.

 

EXERCISES

 

I, Read the following words, paying attention to the place of the stresses and the pronunciation of the suffixes: obvious, numerous, various; magnetize, realize, energize; magnify, solidify, intensify; quality, quantity, equality, retentivity, permeability, reliability, accessibility, applicability.

 

ІІ. Give antonyms for to enter, conductor, to finish, retentivity, to turn off, to reduce, to separate, to forbid, powerless.

 

ІІІ. Give the translation of the following words, paying attention to the suffixes and state to what parts of speech they belong: apply, application, applicable, applicability; allow, allowable, allowance; capable, capability; produce, production, product, productive, productivity; retain, retentivity; magnify, magnification;
permit, permission, permissible.

 

IV. Give examples on the use of the following words and expressions: by... is meant, in order to, the former, the latter, to be familiar, therefore, no longen

 

V. State what part of speech the words in italics belong to and translate the sentences:.

1. Our engineers perfect different devices. 2; These devices are perfect in action. 3. Sometimes a small amount of power is quite sufficient for establishing communication over vast distances. 4. The amount of energy consumed by this motor amounts to that of the engine mentioned above. 5. The subject treated above had to do with some innovations achieved in radio engineering. 6. The apparatus used is subject to sudden changes of temperature. 7 This object has a good reflection surface. 8. Specialists object to this material being used as a filament. 9. Note that the density of the lines of force is the greatest at the poles, 10. The direction of the magnetic field at any point P is arbitrarily chosen as the direction in which a small magnetic needle point would point when placed at P without disturbing appreciably the existing conditions. 11. No line of force crosses another. 12. A freely suspended bar magnet lines itself up parallel with the lines of force existing between the north and south magnetic poles of the earth.

 

VI. Observe the different ways of expressing condition in the following sentences and translate the sentences with the Subjunctive mood: 1. Providing all the requirements were met, the efficiency or the apparatus would be increased. 2. If a natural magnet were suspended by a string from its centre so that it were free to turn, the magnet would be found to turn until the axis through its poles is lying north and south. 3. Had the conductors been moved up and down so as to cut the line of flux of the magnetic field between the poles of the magnets, an e. m. f. would have been generated at the two ends of the conductors. 4. The electric current will flow through a conductor such as a copper wire, if the two ends of the wire are maintained at a difference of potential.

 

VII. Analyse the different functions oi should and translate the following sentences: 1. In order to make the necessary observation the current should be passed for about half an hour. 2. We were sure we should be able to overcome all the difficulties in our research. 3. Should the temperature decrease, the velocity of electrons will decrease too. 4. Were the filament heated, we should get the electron emission. 5. It is essential that we should use iron as one of the principal magnetic substances in the case in question.

 

VIII. Translate the following sentences and observe the different ways of expressing obligation: 1. Where small amounts of power are to be transferred from the generator to the load the condition of maximum power is usually desirable. 2. One ought to know that the electric cell is a device for the transformation of chemical energy into electrical. 3. The electrons in two-element tubes have to go enormous distances before they arrive at the plate with their burden of electricity. 4. It should be pointed out that amplifier tubes act as amplifiers when operated with alternating current on their anodes. 5. When a condenser has an appreciable leakage its resistance must be considered to be in parallel with its e. m. f.

 

IX.Answer the following questions: 1; What do you know about a field in a solenoid? 2. What would happen, if the core absorbed the. straight lines coming out from the sisides of the coil? 3.Why is soft iron used for producing electromagnets? 4. How does the strength of the magnet increase? 5. What is called ampere-turns? 6. What does the strength of the field depend upon? 7. What would take place, if the poles were brought together into U-shape? 8. What is the most obvious use of the electromagnet? 9. Wnat do doctors use electromagnets for? 10. What are the most common applications of the electromagnets?

 

 X. Be ready to talk about electromagnets and their uses.

 

XI. Translate into English: Якщо провідник, який створює замкнутий ланцюг (closed circuit), рухається в магнітному полі так, що він перетинає силові лінії, електрони в провіднику рухатимуться в направленні, яке залежить (1) від направлення потоку магнітного поля і (2) від направлення руху провідника через поле. Величина е. д. з. у провіднику залежатиме від числа ліній, що перетинаються за одиницю часу. Те ж саме спостерігатиметься, коли провідник нерухомий, а силові лінії перетинають (cut through) провідник.

 

XII. Memorize the following terms: line of force, permeability, retentivity, residual magnetizm, core, circuit breaker, remote control.

 

Зворот "for + іменник (займенник) + інфінітив" (for-phrase)

 

Інфінітив, що стоїть після іменника або після займенника в об'єктному відмінку з попереднім прийменником for, виражає дію, яка виконує предмет або особа, позначені даним іменником або займенником.

Зворот "for + іменник + інфінітив" виконує функції різних частин речення (у науковій літературі найчастіше функції обставини мети або наслідку).

Переклад звороту залежить від виконуваної ним функції, при цьому прийменник for опускається, а весь зворот — інфінітив з іменником (займенником) з for — перекладається додатковим речення відповідно виконуваній даним зворотом функції.

Інфінітив англійського речення  відповідає дієслову в особистій формі, тобто функції присудка українського перекладу, а іменник, що стоїть перед інфінітивом — підмету:

For a force to exist there must be two objects involved.

(Інфінітивний зворот стоїть на початку речення, відповідає на питання для чого? і виконує функцію обставини мети ).

Для того, щоб існувала CILW, необхідно, щоб були два предмети.

The temperature was too low for the substance to decompose..

(Інфінітивний зворот співвіднесений з прислівником too, що раніше стоїть, і виконує функцію обставини слідства ).

Температура була дуже низка, для того, щоб речовина розклалася (могло розкластися).

Температура була дуже низка, і розкладання речовини не сталося.

The tendency was for the gas to become ionized.

(Інфінітивний зворот стоїть після дієслова зв'язки be ). Тенденція полягала в тому, що газ ставав іонізованним (Спостерігалася тенденція газу до іонізації).

It is for him to decide..

(Інфінітивний зворот стоїть після дієслова be, яке має модальне значення ). Це повинен він вирішити.

It is possible for the reaction to occur.

(Інфінітивний зворот стоїть в безособовій пропозиції і яв

(Інфінітивний зворот стоїть в безособовому реченні і є частиною предикативного члена).

Можливо, що станеться реакція. Реакція може статися.

 

Примітка. Інфінітив в пасивному стані переводиться дійсним:

It is necessary for the reaction to be accelerated.. Необхідно прискорити реакцію.

The only conclusion for him to make was the following.

(Інфінітивний зворот стоїть після визначуваного ним іменника).

Єдиний висновок, до якого він міг прийти {який він міг зробити), полягав в наступному.

The tendency for the substance to become ionized at high temperatures was investigated.

(Інфінітивний зворот визначає відвернутий іменник tendency ).

Досліджувалася тенденція речовини іонізоваться (до іонізації) під впливом високих температур.

 

Вправа

Перекладіть наступнеі речення , виділяючи зворот "for + іменник (займенник) + інфінітив":

1. The tendency is for the molecule to become agitated. 2. For an observation to be of service two facts must be known. 3. In order for two molecules to react they must be in contact. 4. The motion took place long enough for the bodies to become heated. 5. Under what conditions will the reaction proceed sufficiently rapidly for the method to be practicable? 6. Here is one more important point for the speaker to explain. 7. It is not usual for the phosphatic uranium minerals to be used as a commercial source for uranium. 8. Rusting represents the naturel tendency for the iron to revert from the unstable condition. 9. Two conditions must be met for ductile fraction to occur. 10. The time taken for equilibrium conditions to be set is small. 11. A slow molecule is a nearly stationary target for other molecules to hit.

 

Вправа

Встановите синтаксичну функцію інфінітива і звороту "for + іменник (займенник) + інфінітив" і Перекладіть наступні речення:

1. То obtain the number of watts, we multiply volts by amperes. 2. For a reaction to take place, an A molecule must first meet а В molecule. 3. A small crystal of ice added to the supercooled water is sufficient to cause the appearance of ice. 4. The accuracy of the lunar and solar theories is not sufficient for them to be significant. 5. It is possible to compress this substance. 6. The tendency for a substance to come to a metastable state must be taken into account.