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Файл:Professional English for Electrical Engineers. Part 1. Учебное пособие
.pdf
Exercise 26. Did you know….?
Read the text and then make questions so that the words in bold provide
answers.
Static Electricity
Charge carriers, particularly electrons, can build up, or become deficient, on things
without flowing anywhere. You’ve experienced this when walking on a carpeted floor
during the winter, or in a place where the humidity was low. An excess or shortage of
electrons is created on and in your body. You acquire a charge of static electricity. It’s
called “static” because it doesn’t go anywhere. You don’t feel this until you touch some
metallic object that is connected to earth ground or to some large fixture; but then there is
a discharge, accompanied by a spark.
If you were to become much more charged, your hair would stand on end, because
every hair would repel every other. Like charges are caused either by an excess or a
deficiency of electrons; they repel. The spark might jump an inch, 2 inches, or even 6
inches. Then it would more than startle you; you could get hurt. This doesn’t happen with
ordinary carpet and shoes, fortunately.
In the extreme, lightning occurs between clouds, and between clouds and ground in
the earth’s atmosphere. This spark, called a stroke, is a magnified version of the spark
you get after shuffling around on a carpet. Until the
stroke occurs, there is a static charge in the clouds,
between different clouds or parts of a cloud, and
the ground. In Figure 11, cloud-to-cloud (A) and
cloud-to-ground (B) static buildups are shown. In
the case at B, the positive charge in the earth
follows along beneath the storm cloud. The
current in a lightning stroke is usually several tens
of thousands, or hundreds of thousands, of amperes. Figure 11
But it takes place only for a fraction of a second. Still, many coulombs of charge are
displaced in a single bolt of lightning.
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Exercise 27. Fill in the blanks with prepositions.
1) It is dangerous to go ... a stormy day.
2) Lightning is a very great flash ... light resulting ... a discharge ... atmospheric
electricity.
3) Protecting buildings ... lightning was the first discovery ... the field ... electricity
used ... the good ... mankind.
4) ... thousands ... years people knew nothing ... thunderstorms.
5) Lightning flashes are followed ... thunder which can be heard ... kilometres
around.
6) There is always some danger ... a thunderstorm ... a very high building or a man
standing ... the open field.
7) It is difficult to see a single drop ... water ... the sea.
8) Some scientists ... the past melted metals ... the help ... solar furnaces.
9) Modern civilization cannot do ... electrical appliances.
10) Electric current is necessary ... the operation ... trolley-buses, buses, and modern
trains.
Exercise 28. Compose a dialogue explaining the principles of a spark.
1.4 Molecules
Before you start
1. What is a compound?
2. What is a molecule?
Exercise 29. Read and translate the text.
Different elements can join together to share
electrons. When this happens, the result is a chemical
compound. There are literally thousands of different
chemical compounds that occur in nature. When atoms
of elements join together to form a compound, the
resulting particles are molecules. Figure 12 is an
example of a molecule of water, consisting of three atoms Figure 12
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put together.
The natural form of an element is also known as its molecule. Oxygen tends to
occur in pairs most of the time in the earth’s atmosphere. Thus, an oxygen molecule is
sometimes denoted by the symbol O2. The “O” represents oxygen, and the subscript 2
indicates that there are two atoms per molecule. The water molecule is symbolized H2O,
because there are two atoms of hydrogen and one atom of oxygen in each molecule.
Sometimes oxygen atoms exist all by themselves; then we denote the molecule
simply as O. Sometimes there are three atoms of oxygen grouped together. This is the gas
called ozone, which has received much attention lately in environmental news. It is written
O3.
All matter, whether solid, liquid, or gas, is made of molecules. These particles are
always moving. The speed with which they move depends on the temperature. The hotter
the temperature, the more rapidly the molecules move around. In a solid, the molecules are
interlocked in a sort of rigid pattern, although they vibrate continuously (figure 12A). In a
liquid, they slither and slide around (figure 12B). In a gas, they rush all over the place,
bumping into each other and into solids and liquids adjacent to the gas (figure 12C).
Exercise 30. Transcribe the following words:
Molecule
Oxygen
Symbolize
Environmental
Hydrogen
Chemical
Occur
Rigid
Slither
liquid
Exercise 31. Match the antonyms to the following words.
at rest separation
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solid fastly
fast divide
useful decrease
charge liquid
denote in motion
join invaluable
move slow
compound useless
increase discharge
continuously rest
valuable conceal
Exercise 32. Match the parts of the sentences below.
There are literally thousands of different the more rapidly the molecules move
chemical compounds around.
When atoms of elements join together because there are two atoms of
to form a compound, hydrogen and one atom of oxygen
in each molecule.
The “O” represents oxygen, the resulting particles are molecules.
the subscript 2 indicates
The water molecule is symbolized H2O, although they vibrate continuously.
The hotter the temperature, that there are two atoms per molecule.
In a solid, the molecules are interlocked that occur in nature.
in a sort of rigid pattern,
Exercise 33. Insert the missing words.
1. When this happens, the result is a chemical …….
2. The natural form of an element is also known as its ……..
3. …… tends to occur in pairs most of the time in the earth’s atmosphere.
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4. This is the gas called ….., which has received much attention lately in
environmental news.
5. In a gas, they rush all over the place, bumping into each other and into ….. and
….. adjacent to the gas.
Exercise 34. Define the omitted words and compose 6 sentences with them.
Exercise 35.
a. Make an outline of the text “Molecules”.
b. Retell the text “Molecules” according to the written outline.
Exercise 36. Did you know….?
Read the text and then make questions so that the words in bold provide
answers.
Molecular electronics, also called moletronics, is an interdisciplinary subject that
spans chemistry, physics and materials science. The unifying feature of molecular
electronics is the use of molecular building blocks to fabricate electronic components,
both active (e.g. transistors) and passive (e.g. resistive wires). The concept of molecular
electronics has aroused great excitement, both in science fiction and among scientists. This
is because of the prospect of size reduction in electronics which is offered by molecularlevel control of properties. Molecular electronics provides means to extend Moore’s Law
beyond the foreseen limits of small-scale conventional silicon integrated circuits.
Molecular electronics clearly has the advantage of size. The components of these
circuits are molecules, so the circuit size would inherently range between 1 to 100 NM.
Molecular systems, or systems based on small organic molecules, possess interesting and
useful electronic properties. The rapidly developing area of organic -or plasticelectronics is based on these materials. The investigations of molecular systems that have
been performed in the past have been strongly influenced. Molecular electronics is
reaching a stage of trustable and reproducible experiments. This has lead to a variety of
physical and chemical phenomena recently observed for charge currents owing through
molecular junctions, posing new challenges to theory. The potential application of
molecular electronics has already attracted the interest of some large corporate sectors.
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Exercise 37. Express your understanding of the concept of molecular
electronics and prepare a short report.
1.5 Check Yourself
Refer to the texts in this unit if necessary. A good score is at least 8 correct answers
out of these 10 questions. The answers are listed in the back of this book (Appendix A).
1. The atomic number of an element is determined by
(a) the number of neutrons.
(b) the number of protons.
(c) the number of neutrons plus the number of protons.
(d) the number of electrons.
2. The atomic weight of an element is approximately determined by
(a) the number of neutrons.
(b) the number of protons.
(c) the number of neutrons plus the number of protons.
(d) the number of electrons.
3. Suppose there is an atom of oxygen, containing eight protons and eight neutrons
in the nucleus, and two neutrons are added to the nucleus. What is the resulting atomic
weight?
(a) 8
(b) 10
(c) 16
(d) 18
4. An isotope
(a) is electrically neutral.
(b) has positive electric charge.
(c) has negative electric charge.
(d) can have either a positive or negative charge.
5. A molecule
(a) can consist of a single atom of an element.
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(b) always contains two or more elements.
(c) always has two or more atoms.
(d) is always electrically charged.
6. In a compound,
(a) there can be a single atom of an element.
(b) there must always be two or more elements.
(c) the atoms are mixed in with each other but not joined.
(d) there is always a shortage of electrons.
7. A coulomb
(a) represents a current of 1 ampere.
(b) flows through a 100-watt light bulb.
(c) is equivalent to 1 ampere per second.
(d) is an extremely large number of charge carriers.
8. The attraction or repulsion between two electrically charged objects is called
(a) electromagnetic deflection.
(b) electrostatic force.
(c) magnetic force.
(d) electroscopic force.
9. A stroke of lightning
(a) is caused by a movement of holes in an insulator.
(b) has a very low current.
(c) is a discharge of static electricity.
(d) builds up between clouds.
10. Visible light is converted into electricity
(a) in a dry cell.
(b) in a wet cell.
(c) in an incandescent bulb.
(d) in a photovoltaic cell.
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2 Unit 2. Basic Concepts of Electricity
2.1 Voltage
Before you start
1. What was Volta?
2. What did Volta’s discovery result in?
3. When will voltage influence current?
Exercise 1. Read and translate the text.
When the electrons are poised in that static condition (just like water sitting still,
high in a reservoir), the energy stored there is called potential energy. This potential
energy, stored in the form of an electric charge imbalance and capable of provoking
electrons to flow through a conductor, can be expressed as a term called voltage, which
technically is a measure of potential energy per unit charge of electrons, or something a
physicist would call specific potential energy. Defined in the context of static electricity,
voltage is the measure of work required to move a unit charge from one location to
another, against the force which tries to keep electric charges balanced. In the context of
electrical power sources, voltage is the amount of potential energy available (work to be
done) per unit charge, to move electrons through a conductor.
A battery is an example of an energy storage device that is used to supply a constant
voltage to a circuit (as long as it is sufficiently charged) (figure
13). When a battery is charging it is storing energy, and when
it is discharging it is supplying energy. If it is charged but not
connected to a circuit, then it has the potential to supply energy
by applying voltage to it. Figure 13
Voltage is measured in volts. The abbreviation for volt (or volts) is V. Sometimes,
smaller units are used. The millivolt (mV) is equal to a thousandth (0.001) of a volt. The
microvolt (μV) is equal to a millionth (0.000001) of a volt. It is sometimes necessary to
use units larger than the volt. One kilovolt (kV) is one thousand volts (1000 V). One
megavolt (MV) is 1 million volts (1,000,000 V) or one thousand kilovolts (1000 kV).
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In a dry cell, the voltage is usually between 1.2 and 1.7 V; in a car battery, it is 12 to
14 V. In household utility wiring, it is a low-frequency alternating current of about 117 V
for electric lights and most appliances, and 234 V for a washing machine, dryer, oven, or
stove. In television sets, transformers convert 117 V to around 450 V for the operation of
the picture tube. In some broadcast transmitters, the voltage can be several kilovolts.
The largest voltages on our planet occur between clouds, or between clouds and the
ground, in thundershowers. This potential difference can build up to several tens of
megavolts. The existence of a voltage always means that charge carriers, which are
electrons in a conventional circuit, flow between two points if a conductive path is
provided. Voltage represents the driving force that impels charge carriers to move. If all
other factors are held constant, high voltages produce a faster flow of charge carriers, and
therefore larger currents, than low voltages. But that’s an oversimplification in most reallife scenarios, where other factors are hardly ever constant!
Exercise 2. Match the words to their definitions.
static to put or keep
potential someone or something with the same
quantity or value, or someone having the
same rights as another
store of or producing stationary electrical
charges, as those resulting from friction
provoke to put into action
unit to give or provide something needed
amount a piece of machinery that is used to
perform a task
device that can, but has not yet, come into being;
possible; latent; unrealized; undeveloped
supply something that can conduct or transfer
heat, sound or electricity
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constant any fixed quantity, amount, distance,
measure, etc. used as a standard; specif.
apply a receptacle containing electrodes and an
electrolyte either for generating electricity
by chemical action or for use in
electrolysis
equal to excite to some action or feeling
cell a tool or technique used to do a task
conductive an electronic device in which conduction
by electrons takes place through a vacuum
or a gaseous medium within a sealed glass
or metal container and which has various
uses based on the controlled flow of
electrons
appliance the entire mass of something
tube something that doesn't change or
something that continues or remains
steady
Exercise 3. Transcribe the words from the previous exercise.
Exercise 4. Insert the missing words.
• ….. is the measure of specific potential energy (potential energy per unit
charge) between two locations. In layman’s terms, it is the measure of “push” available to
motivate ……..
• Voltage, as an expression of potential energy, is always relative between two
locations, or …….
• When a voltage source is connected to a circuit, the voltage will cause a
uniform flow of electrons through that circuit called a …….
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