Методические указания и контрольные задания для студентов заочников

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1. To separate electronics from the concepts of electricity is extremely difficult. The field of electricity is generally concerned with magnetism, light, heating and the production of electricity by generators and chemical action.

2. Electronics usually deals with the application of electricity in communications, in radio, television and other devices where vacuum tubes¹ and transistors are employed. We know the vacuum tube and the transistor to be major components of various electronic devices.

3. The many disadvantages of vacuum tubes include high cost, bulky construction, high amount of operating current², limited life and high operating temperature. However the vacuum tube is ideal in many situations where electrical energy is readily available and where heat is no problem.

4. A more recent invention – the transistor is known to have replaced the vacuum tube in many situations. The transistor operates on a minimum amount of electrical energy, emits very little heat and has a long life. The transistor is tiny compared to the size of the vacuum tube of equivalent energy output. This feature has permitted an electronic circuit to be so small that the electronic technician uses magnifying lenses to aid him in his circuit construction and repair.

5. Later research has revealed a device which has revolutionized the field of transistor, Lew Esaki, discovered a simple semiconductor class of crystal that is even more amazing than the transistor. The tunnel diode⁴, as it is called, operates on a negligible amount of electric current, its diameter being some few thousandths of an inch. With such a transistor man will be able to see telephones to be worn on wrists, pocket-size TV sets and ring radio sets⁵.

6. Several recent developments in the field of electronics have led to better ways to communicate efficiently over long distances. The maser and the laser permit man to beam extremely coherent and concentrated energy with almost no loss of intensity. Lasers and masers are known to have been used for transmitting power, radio waves and other waves used in communication.
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Where will lasers and masers be used?

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1. The modern atomic age which we live in began because of an accidental discovery. In 1895 a German scientists named Wilhelm Roentgen discovered the existence of X-rays. Many scientists had studied these rays but no one had discovered that when these cathode rays struck the glass wall of Crookes tube¹ X-rays were created.

2. Roentgen also revealed that these X-rays could pass through solid matter and expose an X-ray film². This discovery led immediately to the use of X-rays in medicine, the use we are all familiar with.

3. Although Roentgen discovered the properties of X-rays he did not know what rays were. He therefore called them X-rays, the X standing for their unknown nature. Today scientists know X-rays to be electromagnetic radiation of extremely high frequency and therefore of extremely short-wave length. X-rays are considered to be produced whenever rapidly moving electrons bombard any solid material. The greater the atomic weight of the material, the more plentiful the X-rays, the greater the speed of the electrons the higher the frequency of the X-rays.

4. As mentioned above X-rays were in a wide use for diagnostic purposes in medicine since their discovery. Industrial radiology has been discovered later particularly for inspecting welds and castings in the automobile and airplane industries. Flaws and cracks inside the metal are readily revealed due to the use of X-ray techniques. Famous paintings are often X-rayed to determine whether they are the originals or forgeries³.

5. Using X-rays irradiation the scientists have learnt to change structures of well-known materials such as metals, ceramics, etc. They could obtain materials of greater strength with higher melting point and particular electrical properties.

6. Radiation is known to be a multagenic agent. In microbiology mutations are increased by irradiation. When a large-scale production of penicillin was introduced the best strain⁴ yielded 100-200 units of penicillin. Being irradiated with X-rays, the same strain produced more than 1,000 units. Many new uses have been found for this treatment in agriculture.

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What increase was obtained in the productivity of penicillin being irradiated with X-rays?

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1. Many of the most serious environment problems of the technological nations result from the use of energy. Every form of energy production is known to cause some damage to the surroundings. A large part of urban air pollution is probably caused by emission from internal combustion engines. Other forms of urban air pollution result from the combustion of coal and low grade oil in steam electric plants or central heating plants.

2. Hydroelectric plants are considered to cause serious problems in the environment as well. One major problem of hydroelectric plants is the enormous weight of the water that fills the lake behind the dam rather quickly after the dam is constructed. The added weight places severe stresses on the geological formation, causing earthquakes in the area. The most severe earthquake- 6,5 on the Richter scale- happened as the lake behind the dam in Konga (India) was filled.

3. Perhaps, the most tragic problem created by the Aswan High Dam on the Nile River is the increase of diseases. The still waters behind the dam prove to create a good ground for insects carrying diseases.

4. Another form of environment degradation common to electric power generation is thermal pollution- the dumping of wasted heat into streams of water or the atmosphere. The warmed water is rather quickly mixed with the streams of water in a lake, this having harmful effect upon ecological balance of the lake.

5. In order to obtain enormous amounts of energy we are building powerful atomic electric stations which open up fine prospects in atomic power industry. However nuclear plants are capable of polluting the environment with radioactive atoms of various elements moreover, nuclear reactors of the types now being built will not be widely used as a source of energy became of the scarcity of the isotope “U” which is used as fuel.

6. The largest potential source of nuclear energy is thermo-nuclear fusion by which the nuclei of small atoms are combined to form large nuclei. However these power plants also contaminate the environment with radioactive elements that are released when the fuel is burnt.
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What substances do power plants contaminate the environment with?

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1. The Earth’s nearest celestial neighbour- the Moon- is only 384,400 km away from us. That is why, it appears sufficiently large and bright. Lunar exploration began in 1959 when Luna-3 spacecraft was sent around the Moon. It radioed back the first photographs of the Moon’s far side. In July 1969 two American astronauts landed on the Moon and carried out a variety of experiments on the surface of the Moon.

2. The kilometers of film exposed by the astronauts, the specimens of rock brought back to the Earth and other data studied by hundreds of scientists from countries all over the Earth have led to new views on several basic problems.

3. Before the Moon landings it was thought that the Moon was a simple body with the same composition throughout. But we now know it to be a body with a metallic core at its centre, a silica- rich mantle and a crust Lunar soils proved to contain a type of structure that is not common on Earth. Small glassy globules were present in the soil.

4. The types of rocks that were encountered on the Moon are familiar to geologists. However, almost all of these rocks have lower proportions of elements with lower melting points than does the Earth. Detailed examinations of the lunar rocks indicate to relatively high proportions of elements with high melting points such as calcium, aluminium and titanium. So the Moon and the Earth seem to be more familiar than had been thought for the last few years. None of the lunar rocks contain any trace of water found inside their minerals. This ends all hope that water and life existed on the Moon at any time in the past.

5. Thus, due to the lunar explorations the scientist were provided with some information about the composition of the solar system, with the information of the Moon and its relationship to the Earth. One day we may be able to use the far side of the Moon as a site for scientific observatories, for optical, ultraviolet or infrared observations. Twenty or thirty years from now we may be able to visit the Moon as researchers or even as tourists.

What purpose will the Moon’s surface be used in future for?

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1. The chemistry of life or biochemistry as chemists call it is an area in which classical fields of chemistry and biology meet. It can be called “molecular biology”. Biochemistry is the study of the structures and reactions of the thousands of compounds involved in life process. Biochemistry is considered to be the most complex area of chemistry.

2. Living things represent the most efficient sophisticated, compact chemical “factories” ever known. How, for example, do cells of the body know when to divide and multiply into new cells having the same characteristics as the original cells? When the body is afflicted by disease or by a wound how does the body protect itself and repair the damage? We know these processes to involve thousands of different chemical compounds.

3. When we compare the nervous system to man-made electronic computers the efficiency and complexity of the biological systems become even more impressive. Despite great advances in computer technology, the greatest computer ever built is almost insignificant being compared to a human brain weighing little more than a kilogram. A computer can perform mathematical operations millions of times faster than a person but what the nervous system can do! For example, it can cause your arm to reach out and touch an object. The brain can translate signals from the retina of the eyes into three dimensional colour images. It can translate a series of frequencies detected by the ear into thoughts whereas a computer can only perform operations being programmed by a person. As to the storage capacity the brain really wins out. The largest computers have storage capacity of about one million “words” but some experts believe the brain to store up all the signals it receives.

4. The chemical processes of our bodies involve enormously complex sequences of reactions, details of these processes being far from complete understanding. Nevertheless the great progress has been made in our understanding of the processes that occur in the body.

5. The first half of this century might be termed the Golden Age of Physics because so many discoveries in understanding the structure of molecules, atoms and nuclei were made. By the same virtue we may be in the midst of a Golden Age in Biochemistry. The next few years of research may bring much increased understanding of chemical processes in cells.