to result in an acceleration — вызывать ускорение

charge — заряд

affect — воздействовать

gravity - сила тяжести, удельный вес

arise — возникать

investigate — исследовать

 mount — количество, сумма

to set up — зд. создавать

Exercise 1.1. Answer the questions:

1. What is the mass of the electron?

2. What is identical for all electrons?

3. How is the sign of the electron charge defined?

4. What are two inseparable aspects of a single unity?

5. What does the electron represent?

6. What does the motion of an electron result from?

7. How can force to an electron be applied?

8.  What sets up an electric field?

9. What sets up a magnetic field?

10. What are the laws of electron motion?

 Exercise 1.2. Find the following words and word combinations in the text:

1. составная часть материи

2. масса электрона составляет

3. электрический заряд

4. одинаковый для всех электронов

5. движение электрона

6. зависит от силы

7. создает электрическое поле

Exercise 1.3. Find the wrong statements and correct them:

1. The properties of the electrons do not change with time.

2. All electrons are identical and have permanent mass and velocity.

3. The electron mass is defined as the ratio of the applied force to the rate of change in the electron velocity.

4. The amount of charge is identical for all electrons.

5. The sign of the charge of the electron is positive.

6. The current affects a magnetic field.

7. An electric field applies a force to the first charge.

Exercise 1.4. Translate into English :

1. Электрон — маленькая, неделимая, основная частица.

2. Свойства электрона не изменяются со временем.

3. Существенные характеристики электрона — масса, заряд.

4. Масса определяется как отношение силы к ускорению.

5. Знак заряда электрона отрицательный.

6. Заряд и масса — два неотделимых аспекта единого целого.

7. Движение электрона зависит от силы, действующей на него.

Exercise 1.5. Translate the 1^st and the 2^nd paragraphes.

Вариант 4

Read the text:

ELECTRON EMISSION

1. The electron tube depends for its action on a stream of electrons that act as current

carriers. To produce this stream of electrons, a special metal electrode (cathode) is present in every tube. But at ordinary room temperatures the free electrons in the cathode cannot leave its surface because of certain restraining forces that act as a barrier. These attractive surface forces tend to keep the electrons within the cathode substance, except for a small portion that happens to have sufficient kinetic energy (energy of motion) to break through the barrier. The majority of electrons move too slowly for this to happen.

2. To escape from the surface of the material, the electrons must perform a certain

amount of work to overcome the restraining surface forces. To do this work, the electrons must have sufficient energy imparted to them from some external source of energy, since their own kinetic energy is inadequate. There are four principal methods of obtaining electron emission from the surface of the material: thermionic emission, photoe-electric emission, field emission, and secondary emission.

3. Thermionic emission. It is the most important and one most commonly used in

electron tubes. In this method the metal is heated, resulting in increased thermal or kinetic energy of the unbound electrons. Thus, a greater number of electrons will attain sufficient speed and energy to escape from the surface of the emitter. The number of electrons released per unit area of an emitting surface is related to the absolute temperature of the cathode and quantity of the work an electron must perform when escaping from the emitting surface.

4. The thermionic emission is obtained by heating the cathode electrically. This may be produced in two ways: (1) by using the electrons emitted from the heating spiral for the conduction of current (direct heating) or (2) by arranging the heating spiral in a nickel cylinder coated with barium oxide which emits the electrons (indirect heating). Normally, the method of indirect heating is used.

5. Photoelectric emission. In this process the energy of the light radiation falling upon the metal surface is transferred to the free electrons within the metal and speeds them up sufficiently to enable them to leave the surface.

6. Field or cold-cathode emission. The application of a strong electric field (i.e. a high positive voltage outside the cathode surface) will literally pull the electrons out of the material surface, because of the attraction of the positive field. The stronger the field is, the greater the field emission from the cold emitter surface is.

7. Secondary emission. When high-speed electrons suddenly strike a metallic surface,they give up their kinetic energy to the electrons and atoms which they strike. Some of the bombarding electrons collide directly with free electrons on the metal surface and may knock them out from the surface. The electrons freed in this way are known as secondary emission electrons, since the primary electrons from some other source must be available to bombard the secondary electron-emitting surface.