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James Watt harnessed steam to meet man's needs for useful power.
Modern hydroelectric power-stations use water power to turn the ma-
chines which generate electricity. The water power may be obtained from
small dams in rivers or from enormous sources of water power like those to be
found in Russia. However, most of our electricity, that is about 86 per cent,
still comes from steam power-stations.
In some other countries, such as Norway, Sweden, and Switzerland, more
electric energy is produced from water power than from steam. They have
been developing large hydroelectric power-stations for the past forty years, or
so, because they lack a sufficient fuel supply. The tendency, nowadays, even
for countries that have large coal resources is to utilize their water power in
order to conserve their resources of coal. As a matter of fact, almost one half of
the total electric supply of the world comes from water power.
The locality of a hydroelectric power plant depends on natural conditions.
The hydroelectric power plant may be located either at the dam or at a consid-
erable distance below. That depends on the desirability of using the head sup-
ply at the dam itself or the desirability of getting a greater head. In the latter
case, water is conducted through pipes or open channels to a point farther
downstream where the natural conditions make a greater head possible.
The design of machines for using water power greatly depends on the na-
ture of the available water supply. In some cases great quantities of water can
be taken from a large river with only a few feet head. In other cases, instead of
a few feet, we may have a head of several thousands of feet. In general, power
may be developed from water by action of its pressure, of its velocity, or by a
combination of both.
A hydraulic turbine and a generator are the main equipment in a hydroe-
lectric power-station. Hydraulic turbines are the key machines converting the
energy of flowing water into mechanical energy. Such turbines have the fol-
lowing principal parts: a runner composed of radial blades mounted on a rotat-
ing shaft and a steel casing which houses the runner. There are two types of
water turbines, namely, the reaction turbine and the impulse turbine. The reac-
tion turbine is the one for low heads and a small flow. Modified forms of the
above turbine are used for medium heads up to 500-600 ft, the shaft being
horizontal for the larger heads. High heads, above 500 ft, employ the impulse
type turbine.
Hydropower engineering is developing mainly by constructing high ca-
pacity stations integrated into river systems known as cascades. Such cascades
are already in operation on the Dnieper, the Volga and the Angara.
TEXT 4
NUCLEAR POWER PLANT
The heart of the nuclear power plant is the reactor which contains the nu-
clear fuel. The fuel usually consists of hundreds of uranium pellets placed in
long thin cartridges of stainless steel. The whole fuel cell consists of hundreds
of these cartridges. The fuel is situated in a reactor vessel filled with a fluid.
The fuel heats the fluid and the super-hot fluid goes to a heat exchanger i.e.
steam generator, where the hot fluid converts water to steam in the heat ex-
changer. The fluid is highly radioactive, but it should never come into contact
with the water that is converted into steam. Then this steam operates steam tur-
bines in exactly the same way as in the coal or oil fired power-plant.
A nuclear reactor has several advantages over power-plants that use coal
or natural gas. The latter produce considerable air pollution, releasing com-
busted gases into atmosphere, whereas a nuclear power plant gives off almost
no air pollutants. As to nuclear fuel, it is far cleaner than any other fuel for op-
erating a heat engine. Furthermore, our reserves of coal, oil and gas are de-
creasing so nuclear fuel is to replace them.
TEXT 5
ELECTRONICS AND TECHNICAL PROGRESS
Large – scale application of electronic techniques is a trend of technical
progress capable of revolutionizing many branches of industry.
Electronics as a science studies the properties of electrons, the laws of
their motion, the laws of the transformation of various kinds of energy through
the media of electrons.
At present it is difficult to enumerate all branches of science and technol-
ogy which are based on electronic technique.
Electronics make it possible to raise industrial automation to a higher
level, to prepare conditions for the future technical retooling of the national
economy. It is expected to revolutionize the system of control over mecha-
nisms and production processes. Electronics greatly helps to conduct funda-
mental research in nuclear physics, in the study of the nature of matter, and in
realization of controlled thermonuclear reactions.
An ever greater role is being played by electronics in the development of
the chemical industry.
Electronics embrace many independent branches. The main among them
are vacuum, semiconductor, molecular and quantum electronics.
TEXT 6
PROTECTION AND CONTROL EQUIPMENT
In electrical systems for the generation, distribution and use of electrical
energy, considerable control equipment is necessary. It can be divided into two
classes:
a) equipment used at the generating and distributing end;
b) equipment used at the receiving end of the system.
c) secondary emission, in which electrons are driven from a material by
the impact of electrons or other particles on its surface.
d) field emission, in which electrons are drawn from the surface of a
metal by the application of very powerful electric fields.
TEXT 7
THE NUCLEUS
The nucleus is composed of protons, neutrons, and other subatomic parti-
cles. The proton is a relatively heavy positive particle. It has exactly the same
quantity of electrical charge as the electron although its sign (or value) is op-
posite. The proton weighs the same as approximately 1845 electrons, and the
atom contains a like number of protons and electrons. The neutron is so named
because it is electrically neutral, that is, it is neither positive nor negative. The
neutron adds weight to the atom and tends to prevent movement of the protons.
When the parts of the atom are examined, there can be found minute par-
ticles with positive and negative electrical charges. The basic difference be-
tween lead and gold lies in the number of electrons and protons in the atoms
which compose these materials (metals).
The simplest atom consists of a nucleus which contains one proton, which
is orbited by a single electron. This is the hydrogen atom. One of the more com-
plex atoms is californium. This atom contains 98 photons and 98 electrons with
the electrons orbiting the nucleus in seven different and distinct energy shells.
TEXT 8
WHAT IS AN ELECTRON?
What is an electron? It is a very small, indivisible, fundamental particle –
a major constituent of all matter. All electrons appear to be identical and to
have properties that do not change with time.
Two essential characteristics of the electron are its mass and its charge.
Qualitatively, an electron is a piece of matter that has weight and is affected by
gravity. Just as the mass of any object is defined, the mass of the electron can be
defined by applying a force and measuring the resulting rate of change in the ve-
locity of the electron, that is, the rapidity with which its velocity changes. This
rate of change is called acceleration, and the electron mass is then defined as the
ratio of the applied force to the resulting acceleration. The mass of the electron is
found to be about 9.11 × 10-28 grams. Not only the electron but all matter appears
to have positive mass, which is equivalent to saying that a force applied to any
abject results in acceleration in the same direction as the force.
How does the other aspect, the charge of the electron, arise? All electrons
have an electric charge, and the amount of charge, like the mass, is identical
for all electrons. No one has ever succeeded in isolating an amount of charge
smaller than that of the electron. The sign of the charge of the electron is con-
ventionally defined as negative; the electron thus represents the fundamental
unit of a negative charge.
TEXT 9
ELECTRONS AND ELECTRONIC CHARGES
An atom of ordinary hydrogen is composed of one positively charged pro-
ton as a nucleus and one negatively charged electron. The proton is about
1,840 times more massive than the electron. Heavier atoms are built up of pro-
tons, neutrons, and electrons. When a body is negatively charged, it has excess
electrons; if positively charged, there is a deficiency of electrons.
In metallic conductors many of the electrons are free to travel about
among the atoms like molecules of a gas.
When electric charges are static, they do not progress in any definite di-
rection. Excess electrostatic charges reside on the outer surface of a conductor,
and their density is greatest in regions of greatest curvature.
TEXT 10
POLARITY
All matter is basically composed of two types of electricity: positive par-
ticles and negative particles. The negative particles are relatively light in
weight and in constant motion. These orbiting particles exhibit equal and op-
posite electrical characteristics to the heavier particles within the nucleus.
When an atom has the same number of electrons as it has protons, it ex-
alts no outward electrical properties. This is because the positive and negative
charges are exactly balanced. Such an atom is electrically stable and is said to
be neutral.
When an atom takes on an excess of electrons, it exhibits outward charac-
teristics similar to the electron. It takes an overall negative property. This con-
dition is called a negative change, and such changed atom is not electrically
stable. A charged atom is called an ion, and if the charge is negative, it is
called a negative ion.
An atom which has less than its normal quota of electrons, displays a
positive polarity similar to that of the proton due to the fact that it has more
positive protons than it has negative electrons. This type of atom is said to as-
sume a positive electrical charge. Such an atom is known as a positive ion
while it is in this electrically unstable condition.
These charges of atoms are the simplest examples of static electricity. We
stated that atoms are influenced to accept or give up electrons.
As the name dynamic electricity indicates, this is electricity in motion.
The heart of the matter is electron movement.
In electrical system, electrical pressure is needed. To maintain this pres-
sure, a device that will move electrons in a way similar to that in which the
pump moves water is necessary. The most familiar is the storage battery.
TEXT 11
ENERGY CONVERSION
Since energy can neither be created nor destroyed, any process of produc-
ing voltage must be a conversion from one form of energy to another. There
are several names for the machines that convert mechanical energy into elec-
trical energy. The dynamo is the source of huge amounts of power; the mag-
neto supplies minute power outputs; and in between there are alternators and
generators. All of these work at the same principle, the principle demonstrated
by Faraday when he discovered that relative motion between a magnetic field
and a conductor in that field would induce a current in the conductor. It makes
no real difference whether the conductor is stationary and the field moving or
the field is stationary and the conductor moving. The important factor is the
relative motion in a manner that will cause flux to cut across the conductor.
ЛИТЕРАТУРА
1. Комолова З. П., Новоселецкая В. П., Новикова Н. В. Популярная электроника. – М.:
ВШ, 1988. – 157 с.
2. Бахчисарайцева М. Э., Каширина В. А., Антипова А. Ф. English for Power Engineer-
ing Students. – М.: ВШ, 1983. – 155 с.
3. Кабо П. Д., Фомичева С. Н. Popular Science Reader. – М.: Просвещение, 1983. – с. 28–37.
4. Четвертакова М. М. Сборник текстов по электротехнике – Санкт-Петербург, 1999. – 48 с.
5. Беляева М. А., Голова З. С., Иванова А. П., Арутюнова К. М. Сборник технических
текстов на английском языке. Учебное пособие для ВТУЗов. Под ред. Н. В. Володина. – М.:
Изд-во литературы на иностранных языках. 1959.