МІНІСТЕРСТВО ОСВІТИ І НАУКИ, МОЛОДІ ТА СПОРТУ УКРАЇНИ

Черкаський політехнічний технікум

Тексти для домашнього читання

з іноземної мови за професійним спрямуванням

для студентів спеціальностей:

5.05070104 “Монтаж і експлуатація електроустаткування підприємств і цивільних споруд”

5.10010102 “Монтаж обслуговування та ремонт електротехнічних установок в агропромисловому комплексі”

(3 курс, V семестр)

Розробив: викладач іноземної мови

А.В.Кособокова

Розглянуто і схвалено цикловою

комісією філологічних дисциплін

Протокол № ____ від _______________ 2012 р.

Голова комісії __________ А.О.Гаврилець

2012

(2441 знаки)

MAN AND HIS MACHINES

In all his activities man now makes use of a lot of machines. Although most of these are of quite recent origin, a few simple ones have come down from ancient times.

The arrow, for example, has been well known to man since prehistoric times, since it was only by hunting that he could get his food. The wheel, one of the greatest inventions ever made by man, is also of prehistoric origin. A two-wheeled carriage is represented widely in his art and literature. The lever is probably of equally ancient origin. It is mentioned by the Greek philosopher Aristotle as a means of lifting a great weight by using a very small force.

After Aristotle there was little change in the number and kind of machines in use for nearly twenty centuries. Since then one new device after another has come to displace others that were less efficient only to be displaced in turn by other devices still faster or better. Let us have a look at a few of these changes.

In going from his home in Mount Vernon to New York to be inaugurated as the first President of America, Washington travelled in a horse-drawn carriage. The roads were extremely difficult to travel. The travel of a little over two hundred miles required seven hard days. That is a speed of about 35 miles a day. Men could travel by land in only two other ways – on foot and on horseback. Within half a century of that time a few short railways had been built in three different parts of the country. At first the trains were drawn by horses; in 1831 the first steam locomotive in America was put into use. The "iron horse" soon proved its efficiency. New lines were designed and old ones extended. The speed of 35 miles a day had given way to regular schedules exceeding 35 miles an hour.

In the first decade of the present century it was thought that the limit of desirable speed had been reached. But the substitution of diesel and electric engines for steam engines and numerous other improvements have shown that much higher speeds may be easily achieved. Modern transportation uses electricity in many ways. Without it transportation, as is known today, could not exist.

On the other hand, life today would be unthinkable with­out modern means of transportation. To reach any part of the world is a matter of hours or days, while a century or two ago it took weeks, sometimes even months or years.

Now let us have a look at a few facts and figures concerning Moscow transport. According to historical documents one-horse cabs appeared in Moscow as early as 1586. Public trans­port was established only in the forties of the last century. The first lines for horse-drawn trams were built in 1872 and those for mechanized trams in 1903. Four years later there were already 800 trams in operation. The first eight buses appeared in the city 40 years ago, while today there are thou­sands in operation. By the way, a Muscovite makes about 800 trips in buses, trolley-buses, the metro, and trams annualy.

Текст № 1 для домашнього читання

для студентів III курсу, 5 семестр (ЕП, ЕС)

Підготував викладач: Кособокова А.В.

(1984 знаки)

Steam turbine

Steam is the principal factor in producing usable energy because of the power created by its expansion. The discovery of the power in steam produced great changes in industry.

Steam power is used mainly in the generation of electric­ity. At present only about 25 per cent of the power used in the Soviet Union is obtained from moving or falling water. Besides electrical power plants are needed in many places where, water power is not available. A great number of electric power stations throughout the country is run by the me­chanical power of steam turbines.

Here is an example of an invention that had to wait many centuries before men discovered its practical application. We mean the steam turbine. More than two thousand years ago a man named Hero who lived in Alexandria, Egypt, made the first steam turbine. It was a steam engine that produced rotary motion. It used neither a piston nor a cylin­der as is the case in steam engines. The steam from a boiler was carried into a ball which had a pair of bent tubes. The steam forced the ball to rotate.

For almost two thousand years men did little with this idea. They did not know how to make the engine perform useful work. Then a few hundred years ago, men began to experiment with this device and came to a simple steam turbine. The ro­tor mounted on a shaft has many small blades around its out­side edge. Nozzles direct jets of steam against these blades causing the rotor to rotate at high speed. This rotary mo­tion can be taken off the rotor shaft by gears to drive other machinery or an electric generator.

A modern turbine usually has not just one but a whole series of bladed disks which together make up the rotor. They are all mounted on a single shaft so that all rotate together. Between each pair of disks there is a stationary ring in which a series of blades is set. The blades curve in the opposite direc­tion from the blades in the rotor. After the steam has passed through the first disk and given the rotor a powerful rotary push, it reverses direction. It then goes through the curved blades on the stationary ring which reverses its direction again, so that it can push against the blades in the second disk. In this way, the steam goes through the turbine, pushing against the rotor blades and changing direction again in the stationary blades and so on. Most of the useful energy in the steam is utilized by the above process.

Текст № 2 для домашнього читання

для студентів III курсу, 5 семестр (ЕП, ЕС)

Підготував викладач: Кособокова А.В.

(2361 знак)

Units of measurement

In measuring the rate at which electrons are moving through a conductor, an electrician could say that the electric current is flowing at the rate of one coulomb per second. How­ever, electricians have a unit which measures it directly and, therefore, instead of using the above-mentioned expression, an electrician would simply say: the current is one ampere. The ampere is the electrical unit which measures directly the quantity of electricity flowing in the conductor. The kiloampere, the largest unit of current, is equal to one thou­sand amperes. Where the ampere is too large a unit to be used, we may employ the milliampere or the microampere, the prefix "milli" meaning a thousandth and "micro" standing for a millionth.

Keep in mind exactly what a volt is because the term is constantly used in all branches of electrical work. It is the practical unit used to measure the pressure that causes the electric current to flow through the circuit. However, it is necessary to have both larger and smaller units. Thus, we have a megavolt (million volts), a millivolt (a thousandth of volt), and a microvolt, that is a millionth of a volt. In electrical circuits, we are also interested in the magni­tude of the resistance in each conductor. Resistance plays a very important part in the operation of every electrical cir­cuit. For that reason, it became necessary that some special practical unit be developed. It would indicate definitely how much resistance were present in any given conductor or cir­cuit. That unit is called the ohm, a megohm equalling one million ohms and a micro-ohm being one millionth of an ohm.

The ohm was named after an experimentor who investigat­ed the resistance taking place in electrical circuits. His name was George Simon Ohm. He carried on numerous experiments which demonstrated that there is a very close relationship between voltage, current, and resistance in any given circuit. He showed that the amount of current which flowed in a cir­cuit depended both upon the amount of resistance in the circuit and the amount of voltage which caused the current to flow.

Having considered the measurement of electrical quanti­ties, we shall define now two units of heat. These are the calorie and the British thermal unit. The first is a metric unit and may be defined as the average amount of heat required to raise the temperature of one gram of water one degree Centigrade. In the same way the British thermal unit, or Btu, is the average amount of heat necessary to raise the tem­perature of one pound of water one degree Fahrenheit. Since the calorie is a rather small quantity of heat, a large unit called the kilogram calorie, or large calorie, is often used. It is not difficult to understand that the kilogram calorie is 1,000 times as large as the calorie which was defined above.

Текст № 3 для домашнього читання

для студентів III курсу, 5 семестр (ЕП, ЕС)

Підготував викладач: Кособокова А.В.

(1582 знаки)