Tiếng anh chuyên ngành kỹ thuật điện, điện tử

TRƯỜNG ĐẠI HỌC QUẢNG BÌNH
KHOA: NGOẠI NGỮ

GIÁO TRÌNH
(Lưu hành nội bộ)

TIẾNG ANH CHUYÊN NGÀNH
ĐIỆN – ĐIỆN TỬ
(Dành cho: Sinh viên ĐH, CĐ CNKT Điện – Điện tử)
Tác giả: Nguyễn Thọ Phước Thảo

Năm 2015
0


MỤC LỤC
Lời nói đầu
Unit 1: Introduction to electricity…………………………………...3
Unit 2: Static electricity……………………………………………..7
Unit 3: Electric current …………...………………………………...10
Unit 4: Powerful sources….………………………………………...13
Unit 5: The electric system………………………...………………..17
Unit 6: Light switch………….……………………………………...20
Unit 7: Knife switch………………………………………………...24
Unit 8: Electric meter….……………………………………………27
Unit 9: Electric gifts………………………………………………...30
Tài liệu tham khảo

1

LỜI NÓI ĐẦU
Điện – Điện tử là một lĩnh vực chuyên ngành riêng biệt. Để đọc hiểu các
văn bản tiếng Anh về điện, điện tử, người học cần có những kiến thức cơ bản về
tiếng Anh và những hiểu biết về lĩnh vực này.
Giáo trình Tiếng Anh chuyên ngành điện – điện tử được biên soạn dựa
trên một số tài liệu tham khảo, sách và giáo trình tiếng Anh chuyên ngành điện,
điện tử của các trường đại học trong nước. Mục đích của giáo trình này nhằm
cung cấp vốn từ vựng, thuật ngữ, kiến thức chuyên ngành đặc trưng trong lĩnh
vực Kỹ thuật điện -điện tử, cá đặc trưng ngữ pháp cơ bản thường sử dụng trong
lĩnh vực chuyên ngành.
Tác giả đã có những chỉnh sửa, bổ sung nhất định để phù hợp với đối
tượng là sinh viên hệ đại học, cao đẳng chuyên ngành kỹ thuật điện-điện tử
trường Đại học Quảng Bình.

2


UNIT 1: INTRODUCTION TO ELECTRICITY
Electricity is the flow of electrical power or charge. It is a secondary energy source
which means that we get it from the conversion of other sources of energy, like coal,
natural gas, oil, nuclear power and other natural sources, which are called primary
sources.
Electricity is our greatest
friend. At home, it lights
bulbs, moves fans, pumps
water and works household
gadgets. In offices and
factories it operates lifts,
runs huge machines and
produces all sorts of goods for us. It carries messages instantly from one corner of the

world to another through telephones, graphs, faxes and computers. It lights the streets
and runs trains. It entertains us through movies and televisions.
The electricity that causes lightning, sparks, crackling noises and attracts objects, and
is contained in things like storm clouds, nylon and plastic, is called static electricity.
Static electricity can be got by rubbing things together and is called static because it
cannot move on its own. Electricity that flows through wires and does work for us,
like lighting a torch or working a fan, is called current electricity. Current electricity is
produced by batteries or by generators in power plants and is supplied to homes.
I. READING COMPREHENSION
*Read the text carefully and answer the questions
1. What is electricity?
2. What are the examples of primary sources?
3. Why can we say that electricity is our greatest friend?
4. How many kinds of electricity are there?
5. What are the differences between static electricity and current electricity?
* True (T) or False (F)
1. Electricity comes from the conversion of primary sources.
2. Storm clouds, nylon, plastic are electricity.
3. Static electricity itself cannot move.
4. Current electricity is the flows of electricity through wires.
5. Battery is a device that produces current electricity.

3


* Match each word in column A with its synonym in column B
A

B

1. Current electricity

a. electricity produced by friction

2. Static electricity

b. a metal conductor that carries electricity
over a distance

3. Bulb

c. the spark of light

4. Wire

e. a flow of electric charge

5. Lightning

f. electric light

II. LANGUAGE FOCUS
1. Simple present and past simple passive (review)
Ex: Current electricity is produced by batteries or by generators in power plants and is
supplied to homes.
* Form: Subject + finite form of to be + Past Participle (V-ed/ column 3)
* Use: We use passive verbs to say what happens to the subject in contrast to active
verbs which are used to say what the subject does.
* Note: Use by if you want to name the person or thing that does/ causes the action.
2. Practice

* Choose the correct verbs form to fill in the blanks provided
1. Light bulb gives light when it……………on. (switches/ is switched)
2. The police believe that electric wire………… the fire in the house. (caused/ was
caused)
3. I …………… an electricity shock from the wire. (got/ was gotten)
4. They had only lived in that house for three years when fire ……….. it (destroyed/
was destroyed)
5. Energy ………..as the capacity for doing work (defines/ is defined)
* Write passive sentences
1. He/ strike/ lightning/ yesterday.
2. Electricity/ use/ widely/ houses/ factories.
3. The electric light bulb/ invent/ Thomas Edison?
4. Static electricity/ usually/ obtain/ rubbing two things.
5. The magnetic field/ create/ a flow of wire/ the wires

4


* Change the following active sentences into the passive voice
1. She pays electricity bill at the end of each month.
2. My hair gets full of static when I brush it.
3. The engineer turned off the electricity.
4. A short circuit causes the fire.
5. They electrified the railway in the 1950s.
III. WRITING AND SPEAKING
* Odd one out
1. electricity

coal

natural gas

oil

2. bulbs

fans

pumps

houses

3. telephones

faxes

graphs

machines

4. movies

televisions

lifts

radios

5. lightning

clouds

spark

thunder

6. torch

batteries

generator

transistor

* Work in groups and make a comparison between the life before electricity and
after electricity.

5


UNIT 2: STATIC ELECTRICITY
Everything we see is made up of tiny little parts called atoms. The atoms are made of
even smaller parts. These are called protons, electrons and neutrons. They are very
different from each other in many ways. One way they are different is their "charge."
Protons have a positive (+) charge. Electrons have a negative (-) charge. Neutrons
have no charge.
Usually, atoms have the same number of electrons and protons. Then the atom has no
charge, it is "neutral." But if you rub things together, electrons can move from one
atom to another. Some atoms get extra electrons. They have a negative charge. Other
atoms lose electrons. They have a positive charge. When charges are separated like

this, it is called static electricity.
If two things have different charges, they attract, or pull towards each other. If two
things have the same charge, they repel, or push away from each other.

So, why does your hair stand up after you take your hat off? When you pull your hat
off, it rubs against your hair. Electrons move from your hair to the hat. Now each of
the hairs has the same positive charge. Things with the same charge repel each other.
So the hairs try to move away from each other. The farthest they can get is to stand up
and away from all the other hairs.

If you walk across a carpet, electrons move from the rug to you. Now you have extra
electrons. Touch a door knob and ZAP! The electrons move from you to the knob.
You get a shock.
I. READING COMPREHENSION
* Answer the questions
1. What are things in our universe made of?
2. What are atoms made of?
3. What kind of charge do electrons and protons have?
4. When is an atom neutral?
5. Why does your hair stand up after you take your hat off?
6


* True (T) or False (F)
1. Air and water are made of atoms.
2. Atoms are smaller than electrons.
3. Neutrons have a negative (-) charge.
4. Two positive (+) charges attract each other.
5. “Repel” means “pull towards each other”
* Fill in the gaps to complete the sentences

1. Atoms are made from electrons, protons and …………….
2. Positive charge and negative charge are……………charges.
3. Static electricity can be obtained by……………two things together.
4. When you pull your hat off, some…………… from your hair move to the hat.
5. If you walk across a carpet, you will get a static…………..
II. LANGUAGE FOCUS
1. A number of and The number of
A number of = “Một số những..”
* Form: A number of + Plural noun + Plural verb
Ex: Wires have a very large number of loose electrons that move about within it in a
random way.
The number of = “ Số lượng những…”
* Form: The number of + Plural noun + single verb
Ex: The number of electrons in oxygen is eight
2. Practice:
* Put a/an or the in the blanks
1. Elements have…………..different number of protons.
2. When an atom is in balance, it has …………. equal number of protons and
electrons.
3. When you pull your hat off, ……….. number of electrons move from your hair to
the hat.
4. Atoms have ……………same number of electrons and protons.
5. As of 2009, the world's most popular battery electric car, the REVAi, is sold in
………… number of countries in Europe and Asia.

7


* Give the correct verbs form
1. The number of protons in an atom…………..(determine) the kind of atom.

2. A number of bulbs ………….(be) suddenly out when we were holding the party.
3. What ………….(be) the number of air conditions in this university?
4. A large number of people in our country still…………(not pay) attention to
conserving electricity.
5. A safety device for a number of electrical loads that are connected to a supply line
between a high-side path and a low-side path.
III. SPEAKING AND WRITING
* Summarize the passage about Static electricity basing on the following diagram
Things in universe

Atoms

Protons
+
(
+
)

Electrons
Neutrons

(
+
)

* Work in groups and find more example of Static electricity

8

UNIT 3: ELECTRIC CURRENT
To light bulb, all you need to do is press a switch. When the switch is on, electric
current flows through the wire. What is this current made of?
Wires have a very large number of loose electrons that move about within it in a
random way. A battery or the mains supply at home pushes these free electrons, so
that they all move in one direction. An electric current consists of a flow of these
electrons.
There are two types of current. DC or
direct current is produced by batteries
and flows in one direction. They are
used in automobiles and flashlights.
AC or alternating current continually
reserves the direction of its flow. The
current supplied to homes and schools
through the mains supply is alternating
current.
Some materials made the light bulb
glow. These materials, like the
aluminum foil, paper clip, coin and the
key allow current to pass through them. They are conductors of electricity. Most
metals are good conductors.
Other materials like wood, glass and rubber are examples of bad conductors of
electricity. They are called insulators.
Insulators are as useful as conductors in making a current flow from one place to
another. We use conductors to carry electricity where it is needed and we use
insulators to prevent it from leaking into places where we do not want it. Wires used
in electrical connections are covered with plastic to make them safe to handle. This is
call insulation.
Pure water is a poor conductor of electricity. Pure water is free of impurities. Tap
water which is not filtered is a good conductor of electricity. Dry air is also a poor

conductor of electricity.
The resistance offered by any material to the flow of current can be measured in terms
of ohms. Conductors have very low resistance while insulators have very high
resistance.
A galvanometer is a current-measuring instrument. It detects the presence of electric
current.

9


I. READING COMPREHENSION
* Answer the questions
1. What is electric current made of?
2. How many types of current are there? What are they?
3. What are the aluminum foil, paper clip, coin and the key called?
4. What do we use insulators for?
5. What is insulation?
* True (T) or False (F)
1. Electric current flows through the wire when the switch is on.
2. Direct current (DC) reserves the direction of its flow.
3. AC stands for alternating current.
4. The unit of resistance is ohms.
5. Metals don’t allow current to pass through them.
6. A galvanometer is a current-measuring instrument.
* Match the words in column A with the phrases in column B to make true
sentences
A

B

1. An electric current

a. flows in one direction

2. Direct current (DC)

b. reserves the direction of its flow.

3. Alternating current (AC)

c. prevent electricity from leaking into other places

4. Conductors

d. measures current

5. Insulators

e. carry electricity

6. A galvanometer

f. is a flow of charge

II. LANGUAGE FOCUS
1. VERB + “-ing” or “to – inf”
+ Verb + “to-inf”: decide, expect, forget, hope, learn, manage…
+ Verb + “-ing”: avoid, consider, like, enjoy, prevent, begin, stop…
2. Practice
* Choose the correct verb form

1. Did you remember to turn off / turning off the electricity when you went on
holiday?

10


2. Don't forget to pay/paying the electricity bill tomorrow.
3. I don’t like to live/living without electricity.
4. This procedure avoids to risk/ risking electrical shorts.
5. Don't forget to check/ checking the electric wires of your car.
* Give the correct verb form in each gap
I used to like going to our local cinema. It was old and rather uncomfortable, but it
has character. Now they’ve stopped…………(show) films there. The owner would
like to go on……….(run) the cinema, but he would need………..(make) a lot of
improvements, which would mean…………(spend) tens of thousands of pounds. I
remember…………(watch) the last film at cinema. It was a murder mystery. It was
five minutes from the end, and we were trying…………(work) out who the murderer
was when suddenly all the lights went out and the film stopped. We sat in the dark for
a few minutes, and then the owner appeared with a torch. “I regret……….(tell) you”.
He said “ that our electricity has failed. I don’t mean…………(disappoint) you, but
I’m afraid we can’t show you the end of the film. We’ve tried…………(phone) the
electricity company, but they say they can’t help”. He went on………….(explain) to
the audience how the film ended. I didn’t understand the story. But I don’t regret
…………..(go) to the cinema on that last evening.

11


UNIT 4: POWERFUL SOURCES
Most of the electricity we use is from the mains supply. The mains supply is

generated in Power Stations, often away from the city, and transmitted by wires to
homes, offices and factories. There is a network of these wires running throughout the
country.
These wires carry a very high voltage to substations where the voltage is reduced. The
reduced voltage is distributed to users through underground cables and overhead
wires.
Electricity from magnets
Power stations produce electricity by the effect of a magnet on a rotating machine.
These are called generators. If a magnet is continually pushed in and out of a coil of
wire, an electric current is produced in the wire. The same thing happens if the wire is
moved instead of the magnet.
A generator makes electricity. A turbine
turns a generator. What turns the
turbine? Some kind of energy is
necessary to turn the turbine. In thermal
power stations, the heat energy from
coal or oil is used to produce steam.
The steam turns the turbine and
generates electricity.
The heat from nuclear fuel can also do
the same job. This is done in nuclear
power stations.
Hydroelectric power stations use the energy of falling water to turn a turbine. For
small generation units, biogas, wind, and tides of seas are also used to rotate the
turbine.
Electricity from chemicals
Batteries use chemical energy to produce electricity. A
reaction between chemicals inside a battery produces a
voltage across its terminals.You know that a battery
always has two terminals, one positive (+) and other

negative (-). When connected to a complete circuit, a
battery produces an electric current. The current flows
from the positive to the negative terminals.

12


Other sources of electricity
Thomas Seebeck discovered that electricity could be
produced by using very hot and cold substances.
When unlike metals are subjected to different
temperatures, very hot and very cold, they produce
electricity. This is called a thermocouple.
Electricity can also be obtained from the sun’s
energy. This is done by Solar Cells.
I. READING COMPREHENSION
* Answer the questions
1. Where is most of electricity from?
2. What is a generator?
3. What rotates the turbine?
4. What are two terminals of a battery?
5. Who discovered that electricity could be produced by using very hot and cold
substances?
* True (T) or False (F)
1. All electricity is from the mains supply.
2. The voltage is distributed to users through underground cables and overhead wires.
3. An electric current is produced in the wire if the wire is moved.
4. In a battery, the current flows from the negative to the positive terminals.
5. The sun’s energy also obtains electricity.
* Choose the best answer

1. The main supply is generated in …………
a. Power Stations

b. Substations

c. Generators

c. Batteries

2. In thermal power stations the heat from ……….is used to produce electricity.
a. coal

b. oil

c. nuclear

c. coal and oil

3. In ……….power stations, the energy of falling water turns the turbine and
generates electricity
a. thermal

b. hydroelectric

c. nuclear

d. water

II. LANGUAGE FOCUS
1. Determiner with of and without of: most, most of, many, many of…

Ex: Most of the electricity
13


* Form: Most of the electricity we use is from the mains supply.
Determiner + of

Determiner without of

+ Before the: most of the electricity

+ most electricity

+ Before this, that…: many of those + many light bulbs
bulbs
+ Before my, her…: a few of my + a few household gadgets
household gadgets
+ some electrical engineers
+ Before it, us…: some of them
* Usage:
+ Determiner + of refers to general things
+ Determiner without of refers to particular ones.
2. Practice
* Put of or nothing into each gap
1. To many………….. people, the most important inventor of all time is Thomas Alva
Edison.
2. Most …………his 1000-plus inventions were devices.
3. Many………… the things he invented played a crucial role in the development of
modern technology, simply by showing what was possible.
4. In so many…………ways, Edison is the perfect example of an inventor.

5. Most………..models have a motorcycle-like throttle that gives a boost while going
up hills or accelerating from a stop.
6. Many…………common electrical measurement instruments are based on electrical
current.
7. Most………..the circuitry inside modern instrumentation cannot be entirely
explained during any introductory course!
8. Most……….death by electrocution is caused by fibrillation, disruption of the
body's nerve signals controlling rhythmic beating of the heart, induced by modest
current flow through the chest area.
9. If you do not plug in the power supply or turn it on, you can work on
most………….circuits without fear of being shocked.
10. Studying the physics behind these discoveries will occupy most………….this
course.

14


* Write some true sentences using some, some of, most, most of, a few, a few of and
then share your sentences with your friends.
III. SPEAKING AND WRITING
*Write a short paragraph (about 150 words) to talk about protecting powerful
sources

15


UNIT 5: THE ELECTRIC SYSTEM
Electricity is generated as it is used. Unlike other commodities, there is very little
ability to store electricity. Because of the instantaneous nature of the electric system,
constant modifications must be made to assure that the generation of power matches

the consumption of power. The electric system we’ve grown to depend on is very
complex and dynamic, ever adjusting to meet changing needs.
The transmission grid
The electrical transmission system is more complex and dynamic than other utility
systems, such as water or natural gas. Electricity flows from power plants, through
transformers and transmission lines, to substations, distribution lines, and then finally
to the electricity consumer.
(Diagram 1)

The electric system is highly interconnected. The interconnectedness of the system
means that the transmission grid functions as one entity. Power entering the system
flows along all available paths, not just from Point A to Point B. The system does not
recognize divisions between service areas, counties, states, or even countries. The
current transmission grid includes not only transmission lines that run from power
plants to load centers, but also from transmission line to transmission line, providing a
redundant system that helps assure the smooth flow of power. If a transmission line is

16


taken out of service in one part of the power grid, the power can usually be rerouted
through other power lines to continue delivering the power to the customer.
In essence, the electricity from many power plants is “pooled” in the transmission
system, and each distribution system draws from this pool. This networked system
helps to achieve a high reliability for power delivery, since any one power plant that
shuts down should only constitute a fraction of the power being delivered by the
power grid.
This pooling of power means that power is provided from a diversity of sources,
including coal, nuclear, natural gas, oil, or other renewable energy sources such as
hydropower, biomass, wind, or solar power.

I. READING COMPREHENSION
*Answer the questions
1. When is electricity generated?
2. What is the operation of the transmission grid?
3. What does “interconnectedness” mean?
4. What does the current transmission grid include?
5. What does the pooling of power mean?
*True (T) or false (F)
1. Electricity can be stored powerfully.
2. The electrical transmission system is more complex and dynamic than natural gas
system.
3. The electric system functions as one entity.
4. Power entering the system flows not just from one point to the other.
5. The current transmission grid includes only transmission lines that run from power
plants to load centers.
II. LANGUAGE FOCUS
1. Conditional sentences type I
* Form: If + Present simple, will-future
Ex: If a transmission line is taken out of service in one part of the power grid, the
power can usually be rerouted through other power lines to continue delivering the
power to the customer.
* Usage: Conditional Sentences Type I refer to the future. An action in the future will
only happen if a certain condition is fulfilled by that time. We don't know for sure
whether the condition actually will be fulfilled or not, but the conditions seems rather
realistic – so we think it is likely to happen.

17


2. Practice

* Choose the correct verb form
1. If we…………so much electricity, the bill………..so large.
a. don’t waste/isn’t

b. don’t waste/ won’t be

c. doesn’t waste/ won’t be

2. What……….if you……………a fork into an electric socket?
a. happen/ put

b. happens/ will put

c. happens/ put

3. If you…………that electric cable, you……………electrocuted.
a. touch/ will be

b. touches/ will be

c. will touch/ are

4. If I………..the President, I…………free electricity to farmers.
a. become/ give

b. become/ will give

c. will become/ will give

5. If she…………four conditioners in our house, she……….too much money on

electricity.
a. don’t have/ will not pay

b. doesn’t have/ will not pay

c. will not have/ will not pay
6. If you…………electricity available at the construction site, it………..the
connection and testing of the pump.
a. have/ will allow b. has/ will allow

c. will have/ will allow

7. If electricity…………available, the well……….drilled and the components set in
place.
a. are not/ will drill b. will not/ can drill c. is not/ can be drilled
* Put the words in order to make sentences
1. If/ two things/ be/ rub/ can/ together/ obtained/ static electricity/ we/,
2. If/ have/ each other/ will/ two things/ attract/ different charges/ they/,
3. If/ pull/ electrons/ move/ your hat/ from/ to/ your hair/ will/ the hat/ off/ you/,/
move
4. If / have/ number/ is/ of/ the same/electrons and protons/ it/ atoms/,/ neutral
5. If / want/ press/ we/ light/ a/ a/ bulb/,/ we/ need/ to/ to/ switch
III. SPEAKING AND WRITING
Work in groups of five; explain the electric system based on the picture 1

18


UNIT 6: LIGHT SWITCH
A light switch is a switch, most commonly used to operate electric lights, permanently

connected equipment, or electrical outlets. Most modern homes have switches set in
the walls, usually 6-10 inches (15-25 cm) away from a door, to operate overhead
ceiling lights. In torches (flashlight) the switch is often near the bulb, but may be in
the tail, or even the entire head itself may constitute the switch (rotated to turn the
light on and off). Home light switches boxes commonly have plastic, ceramic or metal
wall plate covers to prevent accidental contact with live terminals of the switch. Wall
plates are available in different styles and colors to blend in with the style of a room.
The toggle light switch was invented in 1916 by William J. Newton and Morris
Goldberg.

1. TOGGLE LIGHT SWITCH

2. DIMMER SWITCH

The first light-switch employing quick-break technology was invented by John
Holmes in 1884 in the Shield field district of Newcastle-Upon-Tyne. Light switches
are usually built into the walls of the house. Surface mounting is also fairly common
though is seen more in commercial industrial and outbuilding settings than in houses.
Because of electrical safety considerations in many countries their design and
installation is regulated either by law or by widely accepted industry standards. In
practice however in most countries, any requirements for permits or certification are
widely ignored and replacing a light switch is considered a simple "do-it-yourself"
task with the parts being widely available. Because of regulatory issues and the fact
that light switches aren't something that people are usually too bothered with the looks
of, they are usually durable and conservative in design. They frequently remain in
service for many decades, often being changed only when a portion of a house is
rewired. It is not extremely unusual to see century-old light switches still in functional
use.
The dimensions, mechanical designs, and even the general appearance of light switch
change very slowly with time. Manufacturers introduce various new forms and styles,

19


but for the most part decoration and fashion concerns are limited to the faceplates.
Even the "modern" dimmer switch with knob is at least four decades old, and even in
the newest construction the familiar toggle and rocker switch appearances
predominate. The shape and size of the boxes and faceplates as well as what is
integrated (for example in the UK it is normal to have the switch built into the plate)
varies a lot by country.
I. READING COMPREHENSION
* Answer the questions
1. What is a light switch?
2. Where do most modern homes set switches?
3. Why do home light switches boxes commonly have plastic, ceramic or metal wall
plate covers?
4. Who invented the toggle light switch?
5. Why are light switches usually durable and conservative in design?
6. How old is the "modern" dimmer switch with knob?
* True (T) or false (F)
1. All modern homes have switches set in the walls
2. Light switches boxes commonly have plastic, ceramic or metal wall plate covers to
prevent accidental contact with live terminals of the switch.
3. In torches, light switch can be only put in the tail.
4. The first light-switch was invented by John Holmes.
5. The look of the light switches always bothers people first.
6. There are century-old light switches still in functional use.
* Choose the correct answer
1. In torches, the switch is often near the bulb.
A. lights

B. flashlights

C. toggle lights

2. Wall plates are available in different styles and colors to blend in with the style of a
room.
A. compare with

B. belong to

C. suit

3. They are usually durable and conservative in design.
A. long- lasting

B. long

C. available

20


II. LANGUAGE FOCUS
1. Articles: A/an and the
Articles
Definite

Indefinite

The

A/ an

* Usage
- We use "definite" to mean sure, certain. "Definite" is particular.
- We use "indefinite" to mean not sure, not certain. "Indefinite" is general.
- When we are talking about one thing in particular, we use the. When we are talking
about one thing in general, we use a or an.
Ex: 1. A generator makes electricity.
2. In thermal power stations, the heat energy from coal or oil is used to produce
steam. The steam turns the turbine and generates electricity.
2. Practice
* Fill a, an or the in each blank
1. Engineering is…………...large practical action.
2. Electrical engineering is about…………..generation of distribution of electricity
and its many applications.
3. Lightning is………….atmospheric discharge of electricity accompanied by
thunder.
4. Thunder is…………..sound made by lightning.
5. ………….electrical circuit is a network that has………..closed loop, giving a
return path for the current.
* Fill in the blanks with a, an or the

Light bulb
………….doctor of psychology at the insane asylum was doing his normal morning rounds
when he entered………….patient's room. He found Patient 1 sitting on…………floor,
pretending to saw………….piece of wood in half. Patient 2 was hanging from the ceiling, by
his feet………….doctor asked patient 1 what he was doing.
………….patient replied, "Can't you see I'm sawing this piece of wood in half?"

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………..doctor inquired of Patient 1 what Patient 2 was doing.
Patient 1 replied, "Oh. He's my friend, but he's a little crazy. He thinks he's………..light
bulb."
…………..doctor looks up and notices Patient 2's face is flushing red. The doctor asks
Patient 1, "If he's your friend, you should get him down from there before he hurts himself"
Patient 1 replies, "What? And work in……….dark?

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UNIT 7: KNIFE SWITCH
A knife switch is a type of switch used to control the flow of electricity in a circuit. It
is composed of a hinge which allows a metal lever, or knife, to be lifted from or
inserted into a slot or jaw. The hinge and jaw are both fixed to an insulated base, and
the knife has an insulated handle to grip at one end. Current flows through the switch
when the knife is pushed into the jaw. Knife switches can take several forms,
including single throw, in which the "knife" engages with only a single slot, and
double throw, in which the knife hinge is placed between two slots and can engage
with either one. Also, multiple knives may be attached to a single handle and can be
used to activate more than one circuit simultaneously.
Though once common in the early
days of electricity, knife switches
are now rare, finding use largely in
science experiments where the
position of the switch may be
plainly seen in demonstration. The

knife switch is extremely simple in
construction and use, but its
exposed metal parts present a great
risk of electrocution, and the switch
is subject to arcing when opened at
higher voltages, which poses a
further risk of shock or burns to the operator and can cause fires or explosions under
certain conditions.
Open knife switches were supplanted by safety switches with current carrying
contacts inside a metal enclosure which can only be opened by switching off the
power. In modern applications, automatic switches (such as contactors or relays), and
manual switches such as circuit breakers are used. These devices use a snap action
mechanism which opens the switch contacts rapidly, and feature an arc chute where
the arc caused by opening the switch is quenched. These devices also prevent injury
due to accidental contact, as all of the current carrying metal parts of the switch are
hidden within or surrounded with insulated guards.
I. READING COMPREHENSION
* Answer the questions
1. What is a knife switch?
2. When does current flow through the switch?
3. What are the examples of automatic switches?

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4. Why is the knife switch a great risk of electrcution?
5. What devices use a snap action mechanism which opens the switch contacts
rapidly?
* True (T) or False (F)
1. A knife switch is used to control the flow of electricity in a circuit.

2. The hinge is fixed to an insulated base.
3. Knife switches can take one form only.
4. Multiple knives can be used to activate more than one circuit simultaneously.
5. Open knife switches can only be opened by switching off the power.
II. LANGUAGE FOCUS:
1. Comparative and Superlative Adjectives
* Form:
Comparative

Superlative

Short adjective_ER + than + object

The + short adjective_ EST

More + long adjective + than + object

The most + long adjective

* Usage:
- We use the comparative and superlative form to compare and contrast different
objects in English.
+ Use the comparative form to show the difference between two objects.
+ Use the superlative form when speaking about three or more objects to show which
object is 'the most' of something.
Ex: Multiple knives may be attached to a single handle and can be used to activate
more than one circuit simultaneously
2. Practice
* Fill in the correct form of the words in brackets (comparative or superlative)
1. The electricity in the countryside is ……….. the city. (bad)

2. This light bulb is…………….that one. (expensive)
3. I think this is................wire of all. (long)
4. The electricity supply in this company is………….in the others. (good)
5. Electricity is………….friend of ours. (great)

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