Материал: 2048

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- What do you know about the nucleus, the proton and the electron?

- In the electrical system there is a nucleus containing positively charged particles. These particles are called protons. The nucleus is surrounded by Сlighter negatively charged units – electrons. So, the most essential constit-

uent of matter is made up of electrically charged particles. - When matter is neutral?

- Everybody knows that matter having equal amounts of both charges is neutralи- that it produces no electrical effects.

- And what happens if the number of negative charges is unlike the number of positive ones?

- Well, then the matter will produce electrical effects. Having lost some of its electrons, the atom has a positive charge; having an excess of electrons

– it has a negative charge.

- So, as a matter of fact you do know the material. -4-

-When will electrons move?

-If given a path, electrons dislodged from the parent atom, will move.

-Well, what do you know about the electric current?

-The electric current is a quantity of electrons flowing in a circuit per second of time.

-And what is the unit of measure for current?

-The unit of measure for current is the ampere. One coulomb passing a

point in a circuit per second, the current strength is 1 ampere. The apmere is therefore a rate unit.бАД

8. Дайте полное описание природе электрическогоИтока.

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TEXT 2

1. оставьте2 вопроса покартинке (рис.2) и обсудите ихв группе.

Си бАРис.2

2. Прочтите и переведите текст.

ELECTROMOTIVE FORCE

When free electrons are dislodged from the atoms, electrical energy is released and made available to doДwork. Chemical reaction, friction, heat and electromagnetic induction will cause electrons to move from one atom to another. Scientists proved electrical energy to be released from matter by chemical reaction (batteries), heat (thermocouples), electromagnetic induction (generators), and friction (static generators)И. Whenever energy in any form is released, a force is developed. Electrical energy being released, a force called electromotive force (e.m.f.) is developed. And e. m. f. is present, then, whenever free electrons are moved from atoms, any of the abovenamed methods being used to produce such electron motion.

If the force exerts its effort always in one direction, it is called direct; the force changing its direction of exertion periodically is referred to as alternating.

The chemical reaction in a dry cell produces a negative charge or potential on the zinc. This charge being always negative, the e.m.f. is uninderectional (one way). Heat and friction, too are sources of an undirectional force. Elecromagnetic induction, however, is certain to produce an alternating force.

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If the south of a bar magnet is passed into a coil of wire connected to a force-measuring instrument (voltmeter), the meter needle will move in one direction. If the south pole of the magnet is withdrawn from the coil, the needle will move toward the opposite side of the meter, thus showing

the force to be alternating. The direction of force effort is seen to be dependent upon the direction in which the field is cut. The magnitude of the Сelecrical force depends on the conditions at the source, such as the number

of magnetic lines of force per unit of time.

In the battery, the determing factors are kinds of electrolytes and the kind of the metals to be used for the plates. The common dry cell is found to develop 1.5 volts of electrical force regadless of the size of the cell. Large amounts of force can be obtained only by putting many cells in se-

иThe force developed by the generator depends on the number of coils in the armature, on the speed of the armature, and on the strength of the magnetic field from the field magnets, i.e., the number of lines of magnetic force cut by a coil per second. The volt is known to be the unit of

ries.

measure for electrical force.

Wherever an e. m. f. is developed, there is also a field of energy called an electroststic field. This field can be detected by an electroscope;

zink – цинковая пластина (аккумуляторной батареи); uninderectional – однонаправленный;

bar magnet – полосовый магнит; coil – катушка;

needle – игла, стрелка (прибора); armature – якорь (магнита или машины); meter – счетчик; измерительный прибор; plate – анод, пластина, полоса;

in series – последовательно.

4. Прочтите слова из текста и составьте 3 предложения.

Measure, methods, heat, friction, obtain, electrolyte, source, figure, south, field, however, exertion.

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5. Найдите в тексте синонимы следующим словам.

To make, substance, to name, force, to indicate, movement, to receive, amount, since, usual, to apply, velocity, dimension, to definу.

6. Дайте английские эквиваленты следующим словам: зависеть от,

заставлять, при этих условиях, за единицу времени, всякий раз, когда, СибАДИгде бы ни, независимо от, иметься в наличии, вышеупомянутый, по

отношен ю к, больше чем.

7. Найд те конструкц и с инфинитивом в следующих предложениях перевед те предложения на русский язык.

1. A compensator allows the motor to take an exess current without putting a heavy overload on the mains. 2. We know water to flow with less resistance in a large pipe than in one of small section. 3. If we double the force pushing the electrons around the circuit, we expect them to move twice as fast, all other things being equal. 4. To produce a current of one ampere in a copper wire one millimeter in diameter we need that the average velocity of the electrons be only about 001 cm. per second. 5. The only way to stop or control the anode current is to decrease or remove the anode voltage. 6. When the temperature becomes high enough for the atoms to evaporate, the material or solid that they compose rapidly disintegrates. 7. A conducting material allows a continuous current to pass through it under the action of a continuous e. m. f. 8. To measure current, we use an amme-ter connected in series with the resistance. 9. The action of an e. m. f. caus-es electrons to move in some definite direction. 10. To break the electron loose from its atom the force tending to move it is not sufficient.

8. Обсудите одну из следующих тем.

1. Different methods of releasing electrical energy from matter.

2. The development of the electromotive force.

3. The direction of the e. m. f.

4. Batteries as a source of electrical energy.

5. The force developed by the generator.

6. The electrostatic field.

9. Посмотрите видео 1 и передайте его основную идею на английском языке.

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TEXT 3

1. оставьте2 вопроса покартинке (рис.3) и обсудите ихв группе.

СибАДИРис. 3

2. Прочтите текст. В каждом а заце подчеркните ключевое предложение.

FLOW OF ELECTRICITY

Whenever an electric field is set up in a substance by any means whatever a displacement of the electricity in that substance always takes place, the nature of the displacement depending upon the nature of the substance. In every case the positive electricity within the substance is displaced in the direction of the field intensity, the negative electricity being in the opposite direction, until an opposing force of some kind is set up which just balances the forces due to the impressed field.

Conductors of electricity. According to electronic theory, the electron is responsible for a flow of current of electricity. Good conductors are considered to be those substances in which there are present free electrons in constant but indiscriminate motion between the atoms. Under the action of an electromotive force, these free electrons move in some definite direction, resulting in a constant stream of electrons flowing at a phenomenally rapid rate in the conductor. In the case of a uni-directional or direct current,

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