I. LESSON 1. The Electric Current

1. Read and memorize the following words and combinations:

electron- электрон

electric current - электрический ток

conductor - проводник

“direct” current (DC) - постоянный ток

"alternating" current (AC) - переменный ток

to vibrate - вибрировать

resistance - сопротивление, резистор

direction - направление

conducting circuit - проводящая цепь

disadvantage - недостаток

transformer - трансформатор

conduction - проводимость

charge - заряд

ion - ион

visible - видимый

metal wire - металлическая проволока

solid - твёрдое тело

to collide with - сталкиваться с

 

2. Read and translate the following text:

THE ELECTRIC CURRENT

An electric current is a flow of negative particles called electrons. They always move toward the positive terminal of the source of supply.

In a metal there is a large number of electrons which are free and can move through the metal under the action of an electric force. When such an electric force is applied to the metal, these electrons move from one part of the metal to another. Then we say that in the conductor there is an electric current. This flow of electrons through a conductor is similar to the flow of water through a pipe.

The practical application of electricity depends upon the effects produced by the electric current. The engineer has to control the current in order to control the heating, chemical and magnetic effects of electricity.

There are two common types of electric current: "direct" and "alternating". In a "direct" current (DC) the electrons flow steadily from the negative to the positive. In an "alternating" current (AC) they do not flow along at all, they merely vibrate a short distance backwards and forwards.

A direct current is the flow of electrons that starts from a battery or generator, passes through resistances, meters, motors and so on, and finally returns to its starting point. A direct current is used in the electrical system of an automobile \ and an airplane, in the tram, telegraph, telephone, in industry, etc.

A direct current (d. c.) flows continuously through a conducting circuit in one direction ONLY. An alternating current (a. c.) on the other hand, continually reverses in direction. A direct current has one great disadvantage – there is no economic way by means of which one can increase or decrease its voltage.

At present an alternating current is used for lighting, heating and industrial purposes, as this current flowing first in one direction and then in another and its voltage can be increased or decreased with little loss of energy by a transformer.

No one has ever seen an electric current. We only know of the existence of a current by its effects. Conduction is the name normally given to a movement or flow of charges. The charges are usually electrons, but may also be ions.

A metal is made up of tiny crystals which are visible under a microscope. When an electromotive force is applied to the ends of a metal wire the free electrons move in one direction. It is the movement of the free electrons in a conductor that induces an electric current. The greater the number of participating electrons, the greater is the flow of current.

An electric current in a solid is due to the movement of "free" electrons along that solid. Although the molecules are close together within a metallic solid, they do have a movement due to thermal kinetic energy and this movement increases with the temperature.

Conduction of electricity through gases is produced through the medium of ions as in a liquid but the ions are produced in a different manner. Gas ions may result from the bombardment of gas atoms by high-speed electrons or ions, and by the action of electro-, magnetic waves of suitable frequency. If a high-speed electron is projected into a gas, it will collide with some of the molecules of that gas.

 

3. Find in the text the English equivalents:

практическое использование электричества, двигаться в металле, под действием электрического тока, постоянно менять направление, увеличивать напряжение, индуцировать электрический ток, уменьшать напряжение, термическая внутренняя энергия, электрический ток, поток электронов, постоянный ток, переменный ток, работать от генератора, иметь большое преимущество, поток заряженных частиц, электрон, вибрация электронов, ион, недостаток, проводящая цепь.

 

True or False?

1) In a metal there is a large number of electrons which are free and can move through the metal under the action of an electric force.

2) The flow of electrons through a conductor is similar to the tornado.

3) In a "direct" current (DC) the electrons do not flow along at all, they merely vibrate a short distance backwards and forwards.

4) The engineer has to control the current in order to control the heating, chemical and magnetic effects of electricity.

5) A direct current is used for lighting, heating and industrial purposes.

6) No one has ever seen an electric current.

7) A metal is made up of tiny crystals which are visible to the naked eye.

8) The charges are usually electrons, but may also be ions.

9) An electric current in a solid is due to the movement of ions along that solid.

10) If a high-speed electron is projected into a gas, it will collide with some of the molecules of that gas.

 

5. Answer the questions:

1) What is an electric current?

2) How many types of electric current do you know?

3) When can the free electrons move through the metal?

4) To what current is the term d. с applied?

5) How does an alternating current flow?

6) What do we call a "direct" current?

7) What type of current is used now for lighting, heating and industrial purposes?

8) How do we call a movement or flow of charges?

9) Tell about the current flow in solids. Liquids. Gasses.

 

6. Translate orally, and make it fast:

Поток воды в трубке, DC, вибрировать, visible, только в одном направлении, существование электрического тока, transformer, conduction, поток зарядов, conducting circuit, charge, постоянное движение, генератор, metal wire, возвращаться к начальной точке, advantage, ion, сталкиваться с некоторыми молекулами, resistance, AC, индуцировать, двигаться, постоянно менять направление, kinetic energy, electric force, батарея, pipe.

 

7. Find the match in the gap below:

Bombardment through the medium battery little loss of energy pipe depends upon

батарея трубка малая потеря энергии зависит от бомбардировка посредством