Part C

I. Read the following text and entitle it.

1. The working principles of electronics can be demonstrated by tracing the history of radio tubes and photoelectric cells. The history began in 1883, when Thomas Edison found that the heated filament in his incandescent lamp gave off material that blackened the inside of the bulb. This was called the Edison effect, and it led to the development of the modern radio tube. In the Edison effect, also called thermionic emission, heat supplies some electrons in the filament with at least the minimal energy to overcome the attractive forces holding them in the structure of the metal. This discharge of electrons is widely used as a source of electrons in conventional electron tubes—for example, in television picture tubes.

2. In 1887 Heinrich Hertz, while trying to prove the existence of radio waves, discovered the photoelectric effect. If polished metal is given a negative charge and then is flooded with ultraviolet radiation, it steadily loses the charge. Some chemical elements such as cesium and selenium are sensitive to visible light. This discovery led to photoelectric cells.

3. The development of the radio tube began in 1904, when John A. Fleming of England produced the Fleming valve, which today is called a diode, meaning “two electrodes.” He started by heating a filament (also called a cathode) in a vacuum tube with “A-circuit current.” The heat drove electrons out of the filament and into surrounding space. If nothing more happened, the first electrons to escape would soon have formed a negative space charge that would have kept others from being driven out because like charges repel. Fleming avoided this by placing a plate in the tube and connecting the plate and filament through an outside B circuit. The electrons driven from the filament then crossed the tube to the plate and followed the circuit back to the filament. Fleming next placed a battery in the B circuit. The battery was used to supply electrons—that is, negative charges—to the filament, or cathode, and draw them from the plate, or anode, leaving a positive charge. Electrical heating drove electrons steadily from the filament and sent a strong current through the B, or plate, circuit. The strength of the current depends partly upon the heat and partly upon the voltage from the battery. This device could be used as a radio detector.

4. In 1906 the American inventor Lee De Forest transformed the diode into a device that he called an audion, the modern name of which is triode. He did this by inserting a grid of fine wire mesh between the filament and the plate. If variable voltages from an antenna circuit are placed on the filament and the grid, they cause variations in the flow of electrons to the plate. Moreover, the variations in current are much stronger than those caused by the voltage of the incoming signal acting alone. Thus the triode amplifies, or strengthens, the signal.

5. The vacuum tube became the basis of radio, television, and computers, the latter first developed at the end of World War II in 1944 and 1945. The invention of the transistor in 1947 initiated a radical reduction in the size of electronic circuits and in their power requirements. The later development of the integrated circuit set into motion the continuing miniaturization of all electronic devices, which has at the same time greatly increased their speed and computing power.

Notes:

radio tube – электронная лампа

filament – нить накала

incandescent lamp – лампа накаливания

photoelectric cell – фотодиод

II. Answer the following questions on the contents of the text.

1. What discovery led to the modern radio tube?

2. When was the photoelectric effect discovered?

3. What does the Fleming valve consist of?

4. How does a triode differ from a diode?

5. When did the first computers appear?

III. Read the text and say where Thomas Edison’s discovery finds wide application.

IV. Find information about Lee De Forest’s contribution to the development of electronics.

V. List the major steps of electronics history.

VI. Give the main points of the text in 5-6 sentences.

UNIT 2

Part A

Word List

I. Study the following words and choose:

a) nouns

1) reality, real, realistic, realize

2) intense, intensity, intensive, intensification

3) resistant, resist, resistance, resistive

4) development, developed, develop, developing

5) provide, providing, provision, provided

b) adjectives

1) strength, strengthen, strong, strongly

2) differ, differently, difference, different

3) transmissible, transmit, transmission, transmitter

4) inefficiently, efficient, efficiency, efficiently

5) dependence, dependent, depend, independence

c) verbs

1) communication, communicative, communicated, communicate

2) applied, applicable, apply, application

3) installation, installed, installment, install

4) amplify, amplifier, amplified, amplification

5) stimulus, stimulation, stimulate, stimulated

II. Arrange the words of the two groups in pairs:

a) with similar meaning

b) with contrary meaning

III. Match the words with their definitions.

IV. Study the text and try to understand all details.

LASER

1. In the “War of World” written before the turn of the century H. Wells told a fantastic story of how Martians almost invaded our Earth. Their weapon was a mysterious “sword of heat”. Today Wells’ sword of heat has come to reality in the laser. The name stands for light amplification by stimulated emission of radiation.

2. Laser, one of the most sophisticated inventions of man, produces an intensive beam of light of a very pure single colour. It represents the fulfillment of one of the mankind’s oldest dreams of technology to provide a light beam intensive enough to vaporize the hardest and most heat-resistant materials. It can indeed make lead run like water, or, when focused, it can vaporize any substance on earth. There is no material unamenable to laser treatment and laser will have become one of the main technological tools.

3. The applications of laser in industry and science are so many and so varied as to suggest magic. Scientists in many countries are working at a very interesting problem: combining the two big technological discoveries of the second half of the 20-th century – laser and thermonuclear reaction – to produce a practically limitless source of energy. Physicists of this country have developed large laser installations to conduct physical experiments in heating thermonuclear fuel with laser beams. There also exists an idea to use laser for solving the problem of controlled thermonuclear reaction. The laser beam must heat the fuel to the required temperature so quickly that the plasma does not have time to disintegrate. According to current estimates, the duration of the pulse has to be approximately a thousand-millionth of a second. The light capacity of this pulse would be dozens of times greater than the capacity of all the world’s power plants. To meet such demands in practice scientists and engineers must work hard as it is clear that a lot of difficulties are to be encountered on route.

4. The laser’s most important potential may be its use in communications. The intensity of a laser can be rapidly changed to encode very complex signals. In principle, one laser beam, vibrating a billion times faster than ordinary radio waves, could carry the radio, TV and telephone messages of the world simultaneously. In just a fraction of a second, for example, one laser beam could transmit the entire text of the Encyclopedia Britannica.

5. Besides, there are projects to use lasers for long distance communication and for transmission of energy to space stations, to the surface of the Moon or to planets in the solar system. Projects have also been suggested to place lasers aboard Earth satellites nearer to the Sun in order to transform the solar radiation into laser beams, with this transformed energy subsequently transmitted to the Earth or to other space bodies. These projects have not yet been put into effect, because of the great technological difficulties to be overcome and therefore the great cost involved. But there is no doubt that in time these projects will be realized and the laser beam will begin operating in outer space as well.

Notes:

unamenable – неподдающийся

as to suggest magic – можно принять за чудо

put into effect – осуществлять

V. Say whether the following statements are true or false.

1. Laser means “light amplification by stimulated emission of radiation”.

2. Laser produces an intensive beam of light.

3. In the next few years laser will become one of the main technological tools.

4. Martians almost invaded the Earth before the turn of the century.

5. Laser and thermonuclear reaction can produce a limited source of energy.

6. The laser beam heats the fuel so quickly that the plasma disintegrates.

7. There are projects to transform lunar radiation into beams.

8. The laser beam will begin operate in outer space.

Date: 2015-12-13; view: 515; Нарушение авторских прав