II. Put 10 questions to the text.

III. Speak on:

1) direct current;

2) alternating current.

IV. Translate into English.

1. Мы знаем два вида тока: постоянный и переменный.

2. Постоянный ток имеет один большой недостаток.

3. Постоянный ток не изменяется по величине.

4. Ток передается при высоком напряжении.

5. Энергия передается на длинные расстояния с меньшими потерями при высоком напряжении.

6. Ряд заводов выпускает генераторы переменного тока.

V. Give Russian equivalents paying attention to the suffixes.

generator, arrangement, frequency, constitution, widely, measurable, production, transmission, usefulness, width

VI. Give full names to the following abbreviations:

d.c., a.c.. c.p.s, etc., i.e.

VII. Translate paying attention to the words underlined.

1. Owing to semiconductors we are able to convert heat directly into electricity without boilers or other machines.

2. Owing to a transformer we can "transform" high voltage into low voltage and vice versa.

3. Here there is a motion of electrons due to the electric field.

4. Every machine loses energy because of friction.

5. In spite of its usefulness a direct current has one disadvantage.

6. We are able to picture the flow of an alternating current by means of a diagram.

 

VIII. Translate into Russian, paying attention to the Participle.

1. Having measured the potential difference, the students compared the results obtained.

2. Heating a substance, we cause a more rapid motion of its molecules.

3. The results obtained during the last experiment are very important.

4. When living in Moscow, Yablochkov often met with well-known scientists and inventors of that time.

5. The experiment described attracted everybody's attention-

6. The scientist mentioned has made a great contribution to the development of science.

7. When flowing along a conductor, the current heats it.

IX. Translate the sentences paying attention to the Independent Participle Phrase.

1. Academician Petroff was the first scientist who observed the phenomenon known later as the electric arc, his great discovery being the starting point of the modern science of electricity.

2. The word "like" meaning "the same kind", we can say: like charges repel each other, unlike charges attract each other.

3. Two small metal balls are hung from the copper rod, one being supported by a silk string and the other one being supported by a thin copper wire.

4. We saw many electrical installations, some of the devices being connected to the ground.

Lesson 2.

Text.

Conductors and Insulators

Substances which conduct the flow of current electricity or permit electricity to flow through them arc called conductors. Substances which do not permit the flow of electricity are called insulators.

Conductors vary as to their conductivity. In other word's, there are good, medium, and poor conductors. Electricity must he controlled if it is to work for men. There must be a conductor (or path) through which electricity is to travel and also there must be insulators to keep it from "leaking off" the conductor. All materials used in electrical wiring will come under these two headings: either conductors or insulators. Both conductors and insulators are required by us.

We have learned that all matter is made up of atoms, each atom having positive and negative charges of electricity. The movement within a wire of these negative charges, which are called electrons, is interesting. If the electrons are easily moved, then we have a good conductor such as in silver and copper. But otherwise, if the electrons are arranged tightly within a material, such as in glass or mica, it is almost impossible to move them from atom to atom. The latter is true for a good insulator.

The most common conductor is known to be copper in the form of wire. Silver is considered to be a better conductor than copper but it is more expensive and less plentiful.

Copper wires vary in diameter and in the type of insulation, depending upon the use to be made of them. The diameter of the copper wire is measured by means of a wire gauge. The larger the diameter of a copper wire, the more amperage it will carry.

There are many kinds of insulations used on wires, the kind of insulation depending upon the purposes for which the wire is to be used. For instance, for outside wiring, weatherproof insulation is used; for underground or other damp places, lead covering is placed over the insulation.

Words and word combinations:

mica - (мин.)слюда,

to permit –позволять, разрешать

to leak – протекать, стекать, просачиваться

expensive –дорогой

to made up (to consist of) – состоять из

the latter – зд. последний

otherwise –иначе, иным образом, по-другому

likewise – подобно, также, более того

the electrons are arranged tightly –электроны расположены

a gauge – контрольно-измерительный прибор

weatherproof - не поддающийся влиянию погоды

for instance –например

 lead covering – свинцовое покрытие

Assignment:

I. Find in the text the following words and word combinations:

Вещества, позволять, плохой проводник, состоит из, легко двигаются, более дорогой, зависит от целей, измеряется посредством, свинцовое покрытие, считается лучшим проводником, такой как, медный провод,