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Файл:Professional English for Electrical Engineers. Part 1. Учебное пособие
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The design of a typical Leyden jar was a glass bottle
partially filled with water with a metal foil coating the inside of
the bottle and another metal foil covering the outside of the bottle
with a metal wire extending from the inside of the bottle to the
outside through a cork plug.
Electrical charge was stored up in the jar by touching the
conducting wire to an electrical source such as the
aforementioned electric tube. Positive electrons would gather on Figure 4
the inside foil, negative on the outside, thus making a perfect electronic storage device.
It was initially thought that the electricity was stored in the water, but Benjamin
Franklin found that it was actually stored in the glass. Later it was determined that just
about any item could act as the storage device, but that different items would conduct and
store electricity at different rates.
In a letter written in 1748, Franklin described to Collinson how the Leyden jar could
be positively and negatively charged, the first time these terms were used in relation to
electricity. He also, for the first time, used the terms charging and discharging when
describing the transfer of electricity from one object to another. He described his discovery
that the charge was held in the glass of the jar itself.
In order to further study the properties of the electrical storage of glass, Franklin
constructed what he called an electric battery of glass window panes and thin lead plates.
With them he demonstrated how electricity could be passed through and stored in the glass
itself. This is the first description of an electrical battery and the first time such a term was
used.
Exercise 8. Speak on the work of B. Franklin using the words given below.
To prove, unlike, charge, to rub, dissimilar, object, rubber, negative, glass, positive.
1.2 Atoms
Before you start
1. What is the smallest particle known to humans?
2. What are the three particles found in an atom?
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3. What is the atomic number?
Exercise 9. Read and translate the text.
Each chemical element has its own unique type of particle, known as its atom.
Atoms can be divided. It turns out that they are made up of even smaller subatomic
particles called electrons, neutrons, and protons. These subatomic particles are very
important to the understanding of electricity. Electrons carry a negative charge, protons
have a positive charge, and neutrons have no charge at all. It’s the interaction of these
charges that causes the phenomenon we call electricity.
The part of an atom that gives an element its identity is the nucleus. It is made up of
two kinds of particles, the proton and the neutron. These are extremely dense. A
teaspoonful of either of these particles would weigh tons. Every proton in the universe is
just like every other. Neutrons are all alike, too. The number of protons in an element’s
nucleus is known as the atomic number. In general, as the number of protons in an
element’s nucleus increases, the number of neutrons also increases. Elements with high
atomic numbers, like lead, are therefore much denser than elements with low atomic
numbers, like carbon.
For a given element, such as oxygen, the number of neutrons can vary. But no
matter what the number of neutrons, the element keeps its identity, based on the atomic
number. Differing numbers of neutrons result in various isotopes for a given element.
Each element has one particular isotope that is most often found in nature. But all elements
have numerous isotopes. Changing the number of neutrons in an element’s nucleus results
in a difference in the weight, and also a difference in the density, of the element. Thus,
hydrogen containing a neutron or two in the nucleus, along with the proton, is called heavy
hydrogen. The atomic weight of an element is approximately equal to the sum of the
number of protons and the number of neutrons in the nucleus.
This crude model of an atom (figure 5) is that of the element carbon, with six
protons, six neutrons, and six electrons. In any atom, the protons and neutrons are very
tightly bound together, which is an important quality. Neutrons are much less influential
on the chemical character and identity of an atom than protons, although they are just as
hard to add to or remove from the nucleus, being so tightly bound. If neutrons are added
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or gained, the atom will still retain the same
chemical identity, but its mass will change
slightly and it may acquire strange nuclear
properties such as radioactivity.
It’s important to understand the
electrostatic attraction between charges: opposite
charges attract and like charges repel. For
example, two protons will repel each other and
two electrons will repel each other, but a proton Figure 5
will attract an electron (figure 6).
Figure 6
The force of attraction or repulsion depends on two factors: the magnitude of the
individual charges and the proximity of the charges. The magnitude of the individual
charges, whether they are attracting or repelling, directly affects how strongly the force of
attraction or repulsion will be. Since a single proton carries a fixed positive charge and a
single electron carries a fixed negative charge, the magnitude of an individual charge
depends on the number of protons or electrons involved. An atom with two protons, for
example, will have twice the force of attraction to an electron as will an atom with a single
proton.
The force of attraction also varies exponentially as the inverse of the distance
between the charges. If the distance between the two charges is doubled, then the force of
attraction or repulsion will decrease by a factor of four; if the distance is halved, then the
force will increase by a factor of four.
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where force is the magnitude or strength of the force exerted, k is a constant, q1 and q2 are
charges on the particles, and d is the distance between them.
This relationship shows how the force of attraction or repulsion depends on the
magnitude of the two charges, q1 and q2, and the distance of separation. This law of
attraction or repulsion of electrostatic charges is called Coulomb’s law after CharlesAugustin de Coulomb, a French physicist who discovered the relationship.
Exercise 10. Define the following words and expressions.
Proximity
Inverse
Attract
Repel
Exert
Weight
Density
Hydrogen
Interaction
Isotope
Exercise 11. Match the words to their synonyms.
dense division
magnitude react
separation close
decrease fluid
identity feature
bound sameness
liquid rate
quality strength
force to reduce
affect limit
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Exercise 12. What do you know about the interaction between two charges?
Charge 1
Charge 2
Electric force between them
Positive
Positive
Positive
Negative
Positive
Uncharged
Negative
Positive
Negative
Negative
Negative
Uncharged
Define the electric force (repulsion, attraction, no interaction) and complete the table.
Table 1
Exercise 13. Apply the formula.
In a hydrogen atom, the electron (q = –1.60.10-19 C) is 5.29.10-11 m away from the
proton of equal charge magnitude (but opposite sign). Find the electrical force of
attraction.
Exercise 14. Ask 5 questions on the text “Atoms”. Discuss them with your
partner.
Exercise 15.
a. Make an outline of the text “Atoms”.
b. Retell the text “Atoms” according to the written outline.
Exercise 16. Did you know….?
Read the text and then make questions so that the
words in bold provide answers.
Charles Augustin de Coulomb (figure 7) (1736-1806),
French physicist, pioneer in electrical theory, born in
Angouleme. He served as a military engineer for France in the
West Indies, but retired to Blois, France, at the time of the
French Revolution to continue research in magnetism, friction, and Figure 7
electricity. In 1777 he invented the torsion balance for measuring the force of magnetic
and electrical attraction. With this invention, Coulomb was able to formulate the principle,
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now known as Coulomb's law, governing the interaction between electric charges. In
1779 Coulomb published the treatise Theorie des machines simples (Theory of Simple
Machines), an analysis of friction in machinery. After the war Coulomb came out of
retirement and assisted the new government in devising a metric system of weights and
measures. The unit of quantity used to measure electrical charges, the coulomb, was
named for him.
Exercise 17. Prepare a short report about Charles Augustin de Coulomb
according to the plan:
• Biography;
• Scientific discoveries;
• The importance of his works.
1.3 Electrons
Before you start
1. What is an electron?
2. What are the two kinds of electrical charges?
3. What is the difference between electricity at rest and electricity in motion?
Exercise 18. Read and translate the text.
Surrounding the nucleus of an atom are particles
having opposite electric charge from the protons. These
are the electrons.
One of the earliest ideas about the atom pictured
the electrons embedded in the nucleus, like raisins in a
cake. Later, the electrons were seen as orbiting the
nucleus, making the atom like a miniature solar system Figure 8
with the electrons as the planets (figure 8). Still later, this view was modified further.
Today, the electrons are seen as so fast-moving, with patterns so complex, that it is not
even possible to pinpoint them at any given instant of time. All that can be done is to say
that an electron will just as likely be inside a certain sphere as outside. These spheres are
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known as electron shells. Their centers correspond to the position of the atomic nucleus.
The farther away from the nucleus the shell, the
more energy the electron has (figure 9).
Electronic Drift
Some atoms, like copper, silver, and gold, are
structured so that their outer electrons are
weakly bound to the atom and are more easily
pulled from their orbit. Other atoms, like silicon
and germanium, have more tightly bonded outer
electrons that are less likely to be influenced by
Figure 9 external forces.
When any two objects bump into each other they produce friction, and the friction
produces heat. Billions upon billions of electrons are typically flowing in an electrical
circuit, and each collision contributes a small amount of heat. That heat represents the loss
of energy that is converted from electrical energy and dissipated in the form of heat.
Depending on the number of electrons that are flowing and the number of collisions, the
total amount of heat loss in the entire circuit can be significant.
The individual electron flowing in circuit moves only a relatively short distance
before it loses kinetic energy and slows down. When it slows down enough, it falls back
into the orbit of the closest hole or atom that is missing its outer electron(s). The free
electrons move at a relatively slow rate compared to the wave of energy that moves
through the copper. It’s much like the energy of a sound wave that moves through the air.
Individual molecules of air don’t travel horizontally with the wave; rather, they compress
and decompress as the energy of the wave passes. The air is the medium, but the energy is
transferred through it, not with it.
As individual electrons are alternately pulled away from an atom and fall back into
the holes, the net result is that they drift across the sea of atoms at a rate of about a few
millimeters per second. But the resulting transfer of energy is executed at near the speed of
light, which is the speed of electrical transmission.
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Exercise 19. Match the words to their definitions.
opposite not simple; involved or complicated
embed a hard covering on the outside of something
solar the act of colliding, or coming together with
sudden, violent force
complex someone or something that is the reverse of
something else
sphere to relieve of pressure or compression
shell produced by or coming from the sun
pull a closed path or a line forming a boundary
circuit a hollow place, opening or break in something
heat any round body or figure having the surface
equally distant from the center at all points;
collision to set or fix firmly in a surrounding mass
hole a form of energy that causes a difference in
temperature, or the perception of warmth
decompress to make something move toward something
else by tugging or dragging
Exercise 20. The following statements are not true to fact. Correct them.
• All materials are made up of tiny “building blocks” known as electrons.
• All naturally occurring atoms contain particles called molecules, protons, and
ions, with the exception of the protium isotope (1H1) of hydrogen.
• Protons have a negative (-) electric charge.
• Electrons have a positive (+) electric charge.
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• Atoms have no electric charge.
• Molecules can be dislodged from atoms much easier than protons or neutrons.
• The number of neutrons in an atom’s nucleus determines its identity as a
unique element.
Exercise 21. Look at the picture and complete the text.
The nucleus of an atom is made up of (1) ____________
charged protons, (2) ____________ charged electrons and
neutrons with (3) ____________ charge at all. Friction can result
in a separation of charges in a formerly neutral molecule.
Rubbing a plastic rod with wool or a glass rod with silk produces
such charge separation effects. An atom can gain or lose Figure 10
electrons. If it gains (4) ____________, it becomes negatively charged, if it loses electrons
it becomes positively (5) ____________. A “charged” atom is called an “ion.” Electrons
can be made to move from one atom to another. When those electrons move in a “flow”
between the atoms, a current of electricity is created as one electron is attached and
another electron is lost. When electrons move among the atoms of matter, a current of
electricity is created. This is what happens in a piece of wire. The electrons are passed
from (6) ____________ to (7) ____________, creating an electrical current from one end
to the other.
Exercise 22. Define the omitted words and compose 7 sentences with them.
Exercise 23. Match the parts of the sentences below.
Electricity is the transfer of energy the electrons can be pulled free of the
atom.
Electrons are subatomic particles with to be opposite the direction of the
a negative charge orbiting electron flow.
The electrons in some atoms are through the flow of electrons.
When an external force such as a voltage produced by bumping into other
is applied to an element with loosely free electrons produces heat.
bound electrons in the outermost orbit,
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Electron drift is the gradual migration more loosely bound than in other atoms.
The actual path of individual free electrons is or an atom that is missing an electron.
a random zigzag, and the friction
The free electrons may eventually slow down of free electrons toward a positive
and fall into a hole, charge.
The direction of current is considered about the nucleus of an atom in
by most people an electron cloud.
Exercise 24. Answer the following questions.
1. How small is a single atom of copper?
2. If an aluminum atom with a net zero charge has 13 protons, how many
electrons are there in the electron cloud?
3. What is the unit of measure of an electrostatic charge?
4. How many electrons does it take to make up 1 coulomb of electrostatic
charge?
5. Two electrostatic charges are 1 nanometer apart and they have a charge of X
coulombs. (a) If one of them carries a negative charge, what is the polarity of the other
charge? (b) If the distance between the charges is doubled from 1 nanometer to 2
nanometers, what is the resulting force of attraction?
6. What is the speed of electrical transmission in free air?
7. Which is more conductive, tungsten or iron?
8. What is the inverse of resistivity?
9. Why is the direction of current convention opposite that of the flow of
electrons?
battery?
10. Is conventional current flow toward or away from the positive terminal of a
Exercise 25.
a. Make an outline of the text “Electrons”.
b. Retell the text “Electrons” according to the written outline.
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