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flash – a dangerous power which could both kill people and burn or destroy
their houses. The second manifestation of electricity was more or less familiar
to people: a strange yellow stone which looked like glass was sometimes found
in the earth. On being rubbed, that strange yellow stone – amber – obtained the
ability of attracting light objects of a small size. The third phenomenon was
connected with the so-called electric fish which possessed the property of giving
more or less strong electric shocks which could be obtained by a person com-
ing into contact with it.
Nobody knew that the above phenomena were due to electricity. People
could neither understand their observations nor find any practical applications for
them. All of man's knowledge in the field of electricity has been obtained during
the last 370 years. It took a long time before scientists learned how to make use
of electricity. Most of the electrically operated devices, such as the electric lamp, the
refrigerator, the tram, the lift, the radio are less than one hundred years old. In
spite of their having been employed for such a short period of time, they play a
most important part in man's everyday life all over the world.
Famous names are connected with the scientific research on electricity, its
history. As early as about 600 B. C. the Greek philosopher Phales discovered
that when amber was rubbed, it attracted and held minute light objects. How-
ever, he could not know that amber was charged with electricity owing to the
process of rubbing. Then Gilbert, the English physicist, began the first system-
atic scientific research on electrical phenomena. He discovered that various
substances possessed the property similar to that of amber: they generated
electricity when they were rubbed. He gave the name "electricity" to the phe-
nomenon he was studying. He got this word from the Greek "electrum" meaning
«amber».
Many learned men of Europe began to use the new word «electricity» in
their conversation as they were engaged in research of their own. Scientists of
Russia, France and Italy made their contribution as well as the Englishmen and
the Germans.
TEXT 12
FROM THE HISTORY OF ELECTRICITY
There are two types of electricity, namely, electricity at rest or in a static
condition and electricity in motion, that is, the electric current. Both of them
are made up of electric charges, static charges being at rest, while electric cur-
rent flows and does work. Thus, they differ in their ability to serve mankind as
well as in their behaviour.
Static electricity was the only electrical phenomenon to be observed by
man for a long time. At least 2,500 years ago the Greeks knew how to get elec-
tricity by rubbing substances. However, the electricity to be obtained by rub-
bing objects cannot be used to light lamps, to boil water, to run electric trains,
and so on. It is usually very high in voltage and difficult to control, besides it
discharges in no time.
As early as 1753, Franklin made an important contribution to the science
of electricity. He was the first to prove that unlike charges are produced due to
rubbing dissimilar objects. To show that the charges are unlike and opposite,
he decided to call the charge on the rubber-negative and that on the glass-
positive.
In this connection one might remember the Russian academician V. V. Pet-
rov. He was the first to carry on experiments and observations on the electrifi-
cation of metals by rubbing them one against another. As a result he was the
first scientist in the world who solved that problem.
Volta’s discovery of electric current developed out of Galvani's experi-
ments with the frog. Galvani observed that the legs of a dead frog jumped as a
result of an electric charge. He tried his experiment several times and every
time he obtained the same result. He thought that electricity was generated
within the leg itself.
Volta began to carry on similar experiments and soon found that the elec-
tric source was not within the frog's leg but was the result of the contact of both
dissimilar metals used during his observations. However, to carry on such-
experiments was not an easy thing to do. He spent the next few years trying to
invent a source of continuous current. To increase the effect obtained with one
pair of metals, Volta increased the number of these pairs. Thus the voltaic pile
consisted of a copper layer and a layer of zinc placed one above another with a
layer of flannel moistened in salt water between them. A wire was connected
to the first disc of copper and to the last disc of zinc.
The year 1800 is a date to be remembered: for the first time in the world's
history a continuous current was generated.
Volta was born in Como, Italy, on February 18, 1745. For some years he
was a teacher of physics in his home town. Later on he became professor of
natural sciences at the University of Pavia. After his famous discovery he trav-
eled in many countries, among them France, Germany and England. He was
invited to Paris to deliver lectures on the newly discovered chemical source of
continuous current. In 1819 he returned to Como where he spent the rest of his
life. Volta died at the age of 82.
TEXT 13
NATURE OF ELECTRICITY
The first recorded observation on electricity was made by the ancient
Greek philosopher Phales. He stated that a piece of amber rubbed with fur at-
tracted light objects. But more than 22 centuries passed before the study of
magnetism and of electrical phenomena began by Galileo and other scientists.
It was well known that not only amber, but many other substances having
been rubbed behave like amber i. e. can be electrified. It was discovered that
any 2 dissimilar substances forced into contact and then separated became
electrified, or acquired electrical charges.
During the 19th century the idea of the nature of electricity was com-
pletely revolutionized. The atom was regarded as the ultimate subdivision of
matter. Today the atom is regarded as an electrical system. In this electrical
system there is a nucleus containing positively charged particles called pro-
tons. The nucleus is surrounded by lighter negatively charged units – electrons.
So the most essential constituent of matter is made up of electrically charged
particles. Matter is neutral and produces no electrical effects when it has equal
amounts of both charges.
But when the number of negative charge is unlike the number of positive
ones, matter will produce electrical effects. Having lost some of its electrons,
the atom has a positive charge: having an excess of electrons – it has a nega-
tive charge.
TEXT 14
ATMOSPHERIC ELECTRICITY
Electricity plays such an important part in modern life that in order to get
it, men have been burning millions of tons of coal. Coal is burned instead of its
being mainly used as a source of valuable chemical substances which it con-
tains. Therefore, finding new sources of electric energy is a most important
problem that scientists and engineers try to solve.
Hundreds of millions of volts are required for a lightning spark about one
and a half kilometre long. However, this does not represent very much energy
because of the intervals between single thunderstorms. As for the power spent
in producing lightning flashes all over the world, it is only about 1/10,000 of
the power got by mankind from the sun, both in the form of light and that of
heat. Thus, the source in question may interest only the scientists of the future.
Atmospheric electricity is the earliest manifestation of electricity known
to man. However, nobody understood that phenomenon and its properties until
Benjamin Franklin made his kite experiment. On studying the Leyden jar (for
long years the only known condenser), Franklin began thinking that lightning
was a strong spark of electricity. He began experimenting in order to draw
electricity from the clouds to the earth. The story about his famous kite is
known all over the world.
On a stormy day Franklin and his son went into the country taking with
them some necessary things such as: a kite with a long string, a key and so on.
The key was connected to the lower end of the string. "If lightning is the same
as electricity," Franklin thought, "then some of its sparks must come down the
kite string to the key." Soon the kite was flying high among the clouds where
lightning flashed. However, the kite having been raised, some time passed be-
fore there was any proof of its being electrified. Then the rain fell and wetted
the string. The wet string conducted the electricity from the clouds down the
string to the key. Franklin and his son both saw electric sparks which grew big-
ger and stronger. Thus, it was proved that lightning is a discharge of electricity
like that got from the batteries of Leyden jars.
Trying to develop a method of protecting buildings during thunderstorms,
Franklin continued studying that problem and invented the lightning conduc-
tor. He wrote necessary instructions for the installation of his invention, the prin-
ciple of his lightning conductor being in use until now. Thus, protecting build-
ings from strokes of lightning was the first discovery in the field of electricity
employed for the good of mankind.
TEXT 15
MAGNETISM
In studying the electric current, the following relation between magnetism
and the electric current can be observed; on the one hand magnetism is pro-
duced by the current and on the other hand the current is produced from mag-
netism.
Magnetism is mentioned in the oldest writings of man. Romans, for example,
knew that an object looking like a small dark stone had the property of attract-
ing iron. However, nobody knew who discovered magnetism or where and
when the discovery was made. Of course, people could not help repeating the
stories that they had heard from their fathers who, in their turn, heard them
from their own fathers and so on.
One story tells us of a man called Magnus whose iron staff was pulled to
a stone and held there. He had great difficulty in pulling his staff away. Mag-
nus carried the stone away with him in order to demonstrate its attracting ability
among his friends. This unfamiliar substance was called Magnus after its dis-
coverer, this name having come down to us as "Magnet".
According to another story, a great mountain by the sea possessed so much
magnetism that all passing ships were destroyed because all their iron parts fell
out. They were pulled out because of the magnetic force of that mountain.
The earliest practical application of magnetism was connected with the use
of a simple compass consisting of one small magnet pointing north and south.
A great step forward in the scientific study of magnetism was made by
Gilbert, the well-known English physicist (1540–1603). He carried out various
important experiments on electricity and magnetism and wrote a book where
he put together all that was known about magnetism. He proved that the earth
itself was a great magnet.
Reference must be made here to Galileo, the famous Italian astronomer,
physicist and mathematician. He took great interest in Gilbert's achievements
and also studied the properties of magnetic materials. He experimented with
them trying to increase their attracting power.
At present, even a schoolboy is quite familiar with the fact that in mag-
netic materials, such as iron and steel, the molecules themselves are minute mag-
nets, each of them having a north pole and a south pole.
TEXT 16
MAGNETIC EFFECT OF AN ELECTRIC CURRENT
The invention of the voltaic cell in 1800 gave electrical experimenters a
source of a constant flow of current. Seven years later the Danish scientist and
experimenter Oersted, decided to establish the relation between a flow of cur-
rent and a magnetic needle. It took him at least 13 years more to find out that a
compass needle is deflected when brought near a wire through which the elec-
tric current flows. At last, during a lecture he adjusted, by chance, the wire paral-
lel to the needle. Then, both he and his class saw that when the current was
turned on, the needle deflected almost at right angles towards the conductor.
As soon as the direction of the current was reversed, the direction the needle
pointed in was reversed too.
Oersted also pointed out that provided the wire were adjusted below the
needle, the deflection was reversed.
The above-mentioned phenomenon highly interested Ampere who re-
peated the experiment and added a number of valuable observations and state-
ments. He began his research under the influence of Oersted's discovery and
carried it on throughout the rest of his life.
Everyone knows Ampere's rule thanks to which the direction of the magnetic
effect of the current can always be found. Ampere established and proved that
magnetic effects could be produced without any magnets by means of electricity
alone. He turned his attention to the behaviour of the electric current in a single
straight conductor and in a conductor that is formed into a coil, i.e. a solenoid.
When a wire conducting a current is formed into a coil of several turns,
the amount of magnetism is greatly increased.
It is not difficult to understand that the greater the number of turns of wire,
the greater is the m.m.f. (that is the magnetomotive force) produced within the
coil by any constant amount of current flowing through it. In addition, when
doubling the current, we double the magnetism generated in the coil.
A solenoid has two poles which attract and repel the poles of other mag-
nets. While suspended, it takes up a north and a south direction exactly like the
compass needle. A core of iron becomes strongly magnetized if placed within
the solenoid while the current is flowing.
PART II
INTERESTING FACTS
ON ELECTRICITY AND ELECTRONICS
TEXT 1
ELECTRICITY MAY BE DANGEROUS
Many people have had strong shocks from the electric wires in a house.
The wires seldom carry current at a higher voltage than 220, and a person who
touches a bare wire or terminal may suffer no harm if the skin is dry. But if the
hand is wet, he may be killed. Water is known to be a good conductor of elec-
tricity and provides an easy path for the current from the wire to the body. One
of the main wires carrying the current is connected to earth, and if a person
touches the other one with a wet hand, a heavy current rill flow through his
body to earth and so to the others. The body forms part of an electric circuit.
When dealing with wires and fuses carrying an electric current, it is best
to wear rubber gloves. Rubber is a good insulator and will not let the current
pass to the skin. If no rubber gloves can be found in the house, dry cloth gloves
are better than nothing. Never touch a bare wire with the wet hand, and never,
in any situation, touch a water pipe and an electric wire at the same time.
People use electricity in their homes every day but sometimes forget that
it is a form of power and may be dangerous. At the other end of the wire there
are great generators driven by turbines turning at high speed. One should re-
member that the power they generate is enormous. It can burn and kill, but it
will serve well if it is used wisely.
TEXT 2
POWER TRANSMISSION
They say that about a hundred years ago, power was never carried far
away from its source. Later on, the range of transmission was expanded to a
few miles. And now, in a comparatively short period of time, electrical engi-
neering has achieved so much that it is quite possible, at will, to convert me-
chanical energy into electrical energy and transmit the latter over hundreds of
kilometres and more in any direction required. Then in a suitable locality the
electric energy can be reconverted into mechanical energy whenever it is de-
sirable. It is not difficult to understand that the above process has been made
possible owing to generators, transformers and motors as well as to other nec-
essary electrical equipment. In this connection one cannot but mention the
growth of electric power generation in this country. The longest transmission
line in pre-revolutionary Russia was that connecting the Klasson power-station
with Moscow. It is said to have been 70 km long, while the present Volgograd–
Moscow high-tension transmission line is over 1000 kilometres long. (The
reader is asked to note that the English terms "high-tension" and "high-
voltage" are interchangeable.)
It goes without saying that as soon as the electric energy is produced at the
power-station, it is to be transmitted over wires to the substation and then to the
consumer. However, the longer the wire, the greater is its resistance to current
flow. On the other hand, the higher the offered resistance, the greater are the heating
losses in electric wires. One can reduce these undesirable losses in two ways,
namely, one can reduce either the resistance or the current. It is easy for us to see
how we can reduce resistance: it is necessary to make use of a better conducting
material and as thick wires as possible. However, such wires are calculated to
require too much material and, hence, they will be too expensive. Can the current
be reduced? Yes, it is quite possible to reduce the current in the transmission sys-
tem by employing transformers. In effect, the waste of useful energy has been
greatly decreased due to high-voltage lines. It is well known that high voltage
means low current, low current in its turn results in reduced heating losses in
electrical wires. It is dangerous, however, to use power at very high voltages for
anything but transmission and distribution. For that reason, the voltage is always
reduced again before the power is made use of.
TEXT 3
HYDROELECTRIC POWER-STATION
Water power was used to drive machinery long before Polzunov and