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DEMOCRATIC AND POPULAR ALGERIAN REPUBLIC

MINISTRY OF THE SUPERIOR TEACHING AND THE SCIENTIFIC RESEARCH

SUPERIOR NORMAL SCHOOL OF TECHNICAL TEACHING OF ORAN

Department of electrical engineering

TECHNICAL ENGLISH FOR GRADUATE

STUDENTS

COMPOSITION AND SUMMARISING

LESSON 2

First name: Abel!aer

Famil" name: Mec#ernene

Option of t#e magister:

Anal"sis an comman of electrics mac#ines

$ni%ersit" "ear: &''( ) &''*

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TECHNICAL ENGLISH FOR GRADUATE STUDENTS

V. COMPOSITION AND SUMMARISING:

5.1. Revision exercise

Fi!! in "#e $%&s 'i"# % s(i"%)!e 'or* or &(" "#e 'or* in )r%c+e"s in i"s correc" ,or-.

1 In an amplitude modulation receiver, a resonant circuit is (se*to pick up the wanted radio station.

/ The resonant circuit"(neto oscillate at exactly the frequency of the required carrier wave.

0 This carrier and this only is picked up.

2 The modulated carrier from the resonant circuit is ,ee*to an amplifier.

5 The output of'%veamplifying circuit can then be fed to a loudspeaker.

3 The volume is con"ro!!e*by a variable resistor.

4 I" is very simple to remember, isn't it

!t the output of an amplifier, the signal is s"ron$erthan the input.

6 "usic is "r%ns-i""e*through space using electromagnetic waves.

17 T#isprocess is called broadcasting.

11 "ohamed is the o!*es"student of the group.

1/ #y travelling ,%s"er %n* ,%s"erthan sound, an aeroplane breaks the sound barrier.

10 $esting is -ore &!e%s%n"than working in a classroom.

12 !li is considered as the )es"student in the group.

15 %xcuse me& I want a chemistry book and physics one.

13 !re "#esebooks for sale I want "#%"red one.

14 o& #ut "#oseones by my side are.

1 T#isis my desk and "#%"is yours.

16 If you don't put off the heater, it will get #o""er %n* #o""er./7 %ach frame is )(i!"up by first scanning the odd(numbered lines and then the even.

/1 )an you hear the headmaster c%!!

// I watched the train !e%vin$the station.

5./ Co-&osi"ion

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TECHNICAL ENGLISH FOR GRADUATE STUDENTS

The most important qualities of a good explanation are clearness, accuracy and careful arrangement

%xplain briefly how a system or an equipment of your choice works.

T#e e!ec"ric -o"or o, *irec" c(rren"

The electric motors are devices that transform the electrical energy in mechanical one. There aremotors to direct current and alternating current.

The working of motors comes of a physical principle discovered by !ndr- "arie !mpre in /012. 3e

noted that an electrical wire placed in a magnetic field and crossed by a current, was submitted to a

mechanical strength.

The motor of direct current is composed of two distinct mechanical elements:

( T#e s"%"or: It is constituted of a magnetic circuit and its coil, "#e in*(cin$ coi! orin*(c"or, that

produces the inductive magnetic field when it is crossed by a direct current, it is called current of

excitation.

( T#e ro"or: It is the rotating part of the machine and it carries "#e in*(ce* coi!, it includes wire

witch cross the magnetic field.

To start the motor, it is necessary to apply a direct voltage to extremities of the induced coil, it i

crossed by a current and the rotor is submitted to a mechanical couple and turn.

Two voltage feed are necessary to use a motor to direct current:

( the first to feed the induced coil, and is delivered by the electric network.

( the second to feed the inducing coil and to produce the magnetic field and is delivered by the electric

network 4self excited motors5 or by an auxiliary voltage feed 4separated excitation motor5:

( the shunt motor 4motor of parallel excitation5,

( the motor of sery excitation,

( the motor of compound excitation.

These motors have so been used in the industry, but are currently replaced by the asynchronous motors

The electric motors of direct current are reversible. They can transform the electrical energy in

mechanical energy6 it is the working in direct current generator.

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