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Файл:Professional English for Electrical Specialties. Учебное пособие для СПО
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and soon became interested in improving the steam engines, invented by the English
engineers Thomas Savery and Thomas Newcomen, which were used at the time to pump
water from mines.
Watt determined the properties of steam, especially the relation of its density to its
temperature and pressure, and designed a separate condensing chamber for the steam
engine that prevented enormous losses of steam in the cylinder and enhanced the vacuum
conditions. Watt's first patent, in 1769, covered this device and other improvements on
Newcomen's engine, such as steam-jacketing, oil lubrication, and insulation of the cylinder
in order to maintain the high temperatures necessary for maximum efficiency.
At this time, Watt was the partner of the British inventor John Roebuck, who had
financed his researches. In 1775, however, Roebuck's interest was taken over by British
manufacturer Matthew Boulton, owner of the Soho Engineering Works at Birmingham,
and he and Watt began the manufacture of steam engines. Watt continued his research
and patented several other important inventions, including the rotary engine for driving
various types of machinery; the double-action engine, in which steam is admitted
alternately into both ends of the cylinder; and the steam indicator, which records the
steam pressure in the engine. He retired from the firm in 1800 and thereafter devoted
himself entirely to research work.
The misconception that Watt was the actual inventor of the steam engine arose from
the fundamental nature of his contributions to its development. The centrifugal or flyball
governor, which he invented in 1788, and which automatically regulated the speed of an
engine, is of particular interest today. It embodies the feedback principle of a
servomechanism, linking output to input, which is the basic concept of automation. The
electrical unit, the watt, was named in his honor. Watt was also a renowned civil engineer,
making several surveys of canal routes. He invented, in 1767, an attachment that adapted
telescopes for use in measurement of distances. Watt coined the term horsepower. Watt
died in Heathfield, England, on August 19, 1819. By the time he died, he'd changed
history and was the most honored engineer who had ever lived.
Exercise 37. Prepare a short report about J. Watt according to the plan:
• Biography;
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• Scientific discoveries;
• The importance of his works.
2.5 Energy
Before you start
1. What do we call energy?
2. What unit is energy measured in?
3. What does ‘energy is transferred’ mean?
Exercise 38. Read and translate the text.
Energy is a quantity of work done over a period of time, or the capacity to do work.
Electricity is a form of energy that can be converted to and from mechanical energy, safely
transferred over long distances, harnessed, and used for specific purposes.
Energy and power are two distinct entities. Energy is the product of power and time.
To illustrate the difference between the two, suppose that we have two road cases, one
weighing 25 kilograms and the other weighing 50 kilograms. It takes twice the power to
lift the 50-kilogram case, but it takes the same amount of energy to lift the 25-kilogram
road case twice as high. In these cases, the energy expended is equal.
Physicists measure energy in units called joules. One joule (1 J) is the equivalent of
a watt-second, which is the equivalent of 1 watt of power dissipated for 1 second of time
(1 W s or Ws). In electricity, you’ll more often encounter the watt-hour (symbolized W h
or Wh) or the kilowatt-hour (symbolized kW h or kWh). As their names imply, a watthour is the equivalent of 1 W dissipated for 1 h, and 1 kWh is the equivalent of 1 kW of
power dissipated for 1 h.
A watt-hour of energy can be dissipated in an infinite number of different ways. A
60-W bulb consumes 60 Wh in 1 h, the equivalent of a watt-hour per minute (1 Wh/min).
A 100-W bulb consumes 1 Wh in 1/100 h, or 36 s. Besides these differences, the rate of
power dissipation in real-life circuits often changes with time. This can make the
determination of consumed energy complicated, indeed.
Figure 25 illustrates two hypothetical devices that consume 1 Wh of energy. Device
A uses its power at a constant rate of 60 W, so it consumes 1 Wh in 1 min. The power
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consumption rate of device B varies, starting at zero
and ending up at quite a lot more than 60 W. How do
you know that this second device really consumes 1
Wh of energy? You must determine the area under the
curve in the graph. In this case, figuring out this area is
easy, because the enclosed object is a triangle. The
area of a triangle is equal to half the product of the
base length and the height. Device B is powered up for 72 s, Figure 25
or 1.2 min; this is 1.2/60 = 0.02 h. Then the area under the curve is 1/2 × 100 × 0.02 = 1
Wh.
When calculating energy values, you must always remember the units you’re using.
In this case the unit is the watt-hour, so you must multiply watts by hours. If you multiply
watts by minutes or watts by seconds, you’ll get the wrong kind of units in your answer.
Often, the curves in graphs like these are complicated. Consider the graph of power
consumption in your home, versus time, for a day. It
might look like the curve in Figure 26. Finding the area
under this curve is not easy. But there is another way to
determine the total energy burned by your household
over a period of time. That is by means of a meter that
measures electrical energy in kilowatt-hours. Every
month, without fail, the power company sends its
representative to read your electric meter. This person
takes down the number of kilowatt-hours displayed,
subtracts the number from the reading taken the previous month, Figure 26
and a few days later you get a bill. This meter automatically keeps track of total consumed
energy, without anybody having to go through high-level mathematical calculations to find
the areas under irregular curves such as the graph of Figure 26.
Exercise 39. Give the definitions of the following words and expressions.
Mechanical energy
Distinct entity
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Expend
The power consumption
Power dissipation
Curve
A triangle
Energy values
Multiply
Versus time
Burn
Household
Electric meter
Keep track
Get a bill
Exercise 40.Compose 7 sentences using the words in the previous exercise. Each
sentence should contain 2 words or word expressions above.
Exercise 41. Insert the missing words into the sentences below.
1. Electricity is a form of ….. that can be converted to and from mechanical ….,
safely transferred over long distances, harnessed, and used for specific purposes.
2. It takes twice the …. to lift the 50-kilogram case, but it takes the same amount of
…. to lift the 25-kilogram road case twice as high.
3. One joule (1 J) is the equivalent of a …., which is the equivalent of 1 watt of ….
dissipated for 1 second of time (1 W s or Ws).
4. As their names imply, a watt-hour is the equivalent of 1 … dissipated for 1 …,
and 1 …. is the equivalent of 1 …. of power dissipated for 1 ….
5. If you multiply …. by minutes or …. by seconds, you’ll get the wrong kind of
units in your answer.
6. This person takes down the number of …. displayed, subtracts the number from
the reading taken the previous month, and a few days later you get a bill.
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7. This ….. automatically keeps track of total consumed energy, without anybody
having to go through high-level …. calculations to find the areas under irregular …..
8. But there is another way to ….. the total energy burned by your ……over a period
of time.
9. When calculating energy values, you must always …… the units you’re using.
10. The area of a …… is equal to half the product of the base …. and the …….
Exercise 42. Ask 7 questions using the omitted words from the previous
exercise. Discuss the answers with your partner.
Exercise 43. Translate the sentences below.
1. Основными величинами и параметрами, с помощью которых можно
охарактеризовать электрическую энергию, определить ее качество, есть
общеизвестные из соответствующих разделов физики такие величины и параметры,
как: электрическое напряжение, электрический ток, полная, активная и реактивные
мощности и т.д.
2. Поскольку общее определение энергии – это мощность в единицу времени,
то единицей измерения электрической энергии является киловатт в час (кВт час).
3. Электрическая энергия имеет следующие особенности: она
непосредственно не подлежит визуальному восприятию; легко преобразовывается в
другие виды энергии (например, в тепловую, механическую); достаточно просто и с
большой скоростью передается на большие расстояния; проста в использовании с
помощью машин, установок, приборов; удобна для контроля и управления; качество
ее определяет качество работы оборудования и приборов, которые потребляют эту
энергию; процесс передачи энергии сопровождается ее потерями.
4. Общим для всех электрогенераторов является принцип преобразования
различных видов энергии в электрическую, который заключается в разделении
электрических зарядов противоположного знака и разведении их на некоторое
(межэлектродное) расстояние.
5. В электричестве джоуль обозначает работу, которую совершают силы
электрического поля за 1 секунду при напряжении в 1 вольт для поддержания силы
тока в 1 ампер.
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6. С разработкой электромашинных источников (генераторов) появились
первые электростанции (блок-станции) для питания, в основном, электрического
освещения, а также дополнительно — вентиляторов, насосов и подъемников.
7. Связь электрических и магнитных явлений была установлена в двадцатых
годах прошлого века, когда Ампер и Эрстед доказали, что электрический ток
сопровождается возникновением магнитного поля.
8. Идея П.Н. Яблочкова о централизованном производстве и распределении
электроэнергии претворяется в жизнь, начинается строительство центральных
электростанций переменного тока, однако развивающееся производство требовало
комплексного решения сложнейшей научно-технической проблемы: экономичной
передачи электроэнергии на дальние расстояния и создания экономичного и
надежного электрического двигателя, удовлетворяющего требованиям
промышленного электропривода.
9. Единственным недостатком электрической энергии является «отсутствие
склада готовой продукции», т. е. запасать электроэнергию и сохранять эти запасы в
течение больших сроков человечество еще не научилось, а запасы электроэнергии в
аккумуляторах, гальванических элементах и конденсаторах достаточны лишь для
работы сравнительно маломощных установок, причем сроки хранения этих запасов
ограничены.
10. Применение электрической энергии позволило повысить
производительность труда во всех областях деятельности человека,
автоматизировать и внедрить целый ряд технологических процессов в
промышленности, на транспорте, в сельском хозяйстве и быту, основанных на
новых принципах, ускоряющих, облегчающих и удешевляющих процесс получения
окончательного продукта, а также создать комфорт в производственных и жилых
помещениях.
Exercise 44. Discuss the following points with your partner. Compose a short
report using your answers.
What do we call energy?
What forms of energy do you know?
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What do we call kinetic energy?
What do we call potential energy?
Can energy be created and destroyed?
What machine changes mechanical energy into electric energy?
When is mechanical energy converted into heat?
Can chemical energy be converted into heat?
Work is a force applied over a distance. If twice the force is applied over half the
distance, is the amount of work done the same?
Is electricity a form of energy?
How many BTUs does it take to make 1 kilowatt-hour?
Exercise 45.
a. Make an outline of the text “Energy”.
b. Retell the text “Energy” according to the written outline.
Exercise 46. Did you know…?
Read the text and then make questions so that the words in bold provide
answers.
General Solar Energy Facts
1. Solar energy is the primary source of energy for all life forms.
2. Solar energy is clean. No fossil fuels are used to produce heat or electricity
with solar energy. The only pollution produced is in the manufacturing, transporting
and installing of solar panels.
3. The sun's energy can be used in a variety of ways. Solar power can be used to
cook food, heat and cool homes, warm water and light buildings.
4. Solar thermal power creates electricity by heating water into steam. This heat
can be used to warm the air in your home or the water for your morning shower.
5. California currently has the largest solar power plant in the world.
Covering 1000 acres are nine solar thermal plants in the Mojave Desert.
6. For solar energy to generate electricity, it must be daylight. During night
hours, stored solar energy or an alternative energy source must be used.
7. Photovoltaic Panels (solar panels) are mainly composed of silicon.
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8. Although the initial investment of solar panels is high, energy from the sun is
free. The payback period may take several years, but money will be saved in the long
term.
9. Problems with solar energy may arise in certain locations. Regions that have
an abundance of cloudy, overcast, or rainy days find it hard to benefit from solar
power.
10. Solar energy is measured in kilowatt-hours - 1 kilowatt = 1000 watts.
2.6 Magnetism. Electromagnetism
Before you start
1. Can you name two characteristics that are common to every magnet?
2. Does the flow of current always produce a magnetic field?
3. What is electromagnetism?
Exercise 47. Read and translate the text.
Electric currents and magnetic fields are closely related. Whenever an electric
current flows—that is, when charge carriers move—a magnetic field accompanies the
current. In a straight wire that carries electrical current, magnetic lines of flux surround the
wire in circles, with the wire at the center, as shown
in Figure 27. (The lines of flux aren’t physical
objects; this is just a convenient way to represent
the magnetic field.) You’ll sometimes hear or read
about a certain number of flux lines per unit crosssectional area, such as 100 lines per square
centimeter. This is a relative way of talking about
the intensity of the magnetic field. Figure 27
Magnetic fields are produced when the atoms of certain materials align themselves.
Iron is the most common metal that has this property. The atoms of iron in the core of the
earth have become aligned to some extent; this is a complex interaction caused by the
rotation of our planet and its motion with respect to the magnetic field of the sun. The
magnetic field surrounding the earth is responsible for various effects, such as the
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concentration of charged particles that you see as the
aurora borealis just after a solar eruption.
When a wire is coiled up, the resulting magnetic
flux takes a shape similar to the flux field surrounding
the earth, or the flux field around a bar magnet. Two
well-defined magnetic poles develop, as shown in
Figure 28. Figure 28
The intensity of a magnetic field can be greatly increased by placing a special core
inside of a coil. The core should be of iron or some other material that can be readily
magnetized. Such substances are called ferromagnetic. A core of this kind cannot actually
increase the total quantity of magnetism in and around a coil, but it will cause the lines of
flux to be much closer together inside the material. This is the principle by which an
electromagnet works. It also makes possible the operation of electrical transformers for
utility current.
Magnetic lines of flux are said to emerge from the magnetic north pole, and to run
inward toward the magnetic south pole.
Electromagnetism
In the early nineteenth century, very little was known about electricity. One day in
the spring of 1820, a Danish physicist named Hans Christian Øersted, who taught at
Copenhagen University, stumbled upon a previously unknown phenomenon. While he was
giving a lecture about the heat generated by a current flowing through a platinum wire, he
noticed something that he did not expect. A compass happened to be on his desk in the
vicinity of the wire, and when the current flowed he noticed that the needle deflected. He
had discovered that electricity and magnetism were inextricably linked.
We already know that electrons carry an electrostatic charge and that electricity is
the flow of electrons. Since the discovery of electromagnetism, we understand that electric
current also produces a magnetic field (electromagnetism). If we could see the lines of flux
of that electromagnetic field, we would see concentric rings around the current-carrying
conductor falling off in strength as they get farther from the conductor.
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Following what is known as the right-hand
rule; we can visualize the direction of the magnetic
lines of flux by taking our right hand and wrapping
our fingers around the conductor with our thumb
protruding along the conductor, pointing in the
direction of the current flow.
Our fingers will then indicate the direction of
the magnetic lines of flux, as shown in Figure 29.
The strongest magnetic field is closest to the
conductor, and the strength is inversely proportional
to the square of the distance from the conductor; Figure 29
for example, if the distance from the conductor doubles, then the strength of the magnetic
field drops off by a factor of four.
Exercise 48. Match the words to their definitions.
polarity a condition in the space surrounding some
objects that causes charged or metallic
bodies brought close by to experience
the force of magnetism
attraction the fact or condition of being close in space
or relationship
repulsion a condition where objects move or are pulled
together under the influence of a force
field to coil or twist about or around something
magnetic field having a common center
magnetic lines a condition where objects move or are pulled
apart under the influence of a force
flux the breaking out of a rash or the like
intensity curved lines used to represent a magnetic
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