III. Answer the following questions:
Why does an iron bar become magnetized if you pass electric current through a length of the surrounding wire?
What determines the polarity of an electromagnet?
What is the rotating component of an electric motor called?
How does the commutator reverse the flow of electrical current through the armature?
What is the function of a brush?
Why must the direction of the flow of the current be reversed in order for an electric motor to function? What would happen if the direction remained the same?
How is the power of an electric motor applied in practice?
IV. Match each of these figures with the correct description, A, B, C, or D. One of the descriptions does not match any of the figures. (The figures are in the correct sequence, but the descriptions are not.)
Motor run on direct current
A
The armature turns a quarter of a turn. Then electric contact is broken because of the gap in the commutator, but the armature keeps turning because there is nothing to stop it.
В
When current flows, the armature becomes an electromagnet. Its north pole is attracted by the south pole and repelled by the north pole of the field magnet.
С
When a universal motor is run on direct current, the magnetic poles in the armature change while those of the field magnet remain constant.
D
When the commutator comes back into contact with the brushes, current flows through the armature in the opposite direction. Its poles are reversed and the turn continues.
V. Find in the Text 2 and put down key words that can be used to speak about operating principles of an electric motor.
VI. Match each of these components to its function, and then describe its function in a sentence.
Example: The function of an electric motor is to convert electrical energy to mechanical energy.
Component Function
1. armature a. transfers rotation from the motor
2. bearings b. create an electromagnetic field
3. brushes с. converts electromagnetic energy to rotation
4. commutator d. reverses the current to the armature
5. drive shaft e. support the drive shaft
6. field windings f. supply current to the armature
VII. Match the given words to sentences 1–7.
battery, cable, controller, lamp, solar panel, electrical current, switch
1. shines a light when the switch is on: __________ .
2. converts the sun’s energy into an electric current: __________ .
3. stores electricity: __________ .
4. When a __________ is closed, the electrical current can flow.
5. DC is a type of __________ .
6. Electricity passes through the __________ to the lamp or the battery.
7. carries the electrical current: __________ .
Text 3.
I. Read the text and be ready to do exercises that follow it.
Vocabulary
alternator ['ɔ:ltəneɪtə] – генератор переменного тока
linear alternator – линейный генератор
occasionally [ə'keɪʒənəlɪ] – иногда, изредка
to wind [waɪnd] (wound, wound) – наматывать, обматывать
to offset – балансировать, компенсировать
with respect – по отношению
slip ring – токосъемник
restricted [rɪ'strɪktɪd] – ограниченный
automotive [,ɔ:tə'məutɪv] – автомобильный
to feed [fi:d] (fed, fed) – снабжать, подавать