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1. They are used to pull...

They are used to transform. They were used to count. They will be used to build.

2. When viewed, while doing...

While discussing that interesting question, we argued a lot about it. The direction of a current is anticlockwise when viewed from above.

Exercises

1. Listen, read and translate the text.

2. Answer the following questions in a written form:

1. What purpose are electric motors used for? 2. What fundamental parts of an electric motor do you know? 3. How does a current from a battery flow? 4. When is the current made to reverse? 5. What is called a commutator?

3. Copy these sentences putting "rotates", "the armature",

"a commutator", "repel", "the coil", "a vacuum cleaner"

in the blanks:

1. Electric motors are used to operate ... . 2. ... is the device which automatically changes the direction of the cur­rent in ... . 3. Like poles ... each other. 4. A coil of wire which is wound on a soft iron core is called ... . 5. The com­mutator ... with the coil.

4. Make up and write 6 questions using the words given in the table:

108

Are

Is

Will be Was

Were

they

it

used to

transform energy?

produce sound?

pull trams?

rotate the commutator with the coil?

attract bodies?

produce current?

operate a radio receiver?

5. Make up 5 questions to the following sentences and trans­late them into Russian:

1. The electric motor is a machine which converts electri­cal energy into mechanical energy. 2. The required reversal of current is produced by means of a commutator. 3. The commutator is a split metal ring attached by insulating materials to the spindle on which the loop rotates. 4. The ends of the loop are attached to separate sections of the com­mutator. 5. The current is supplied to the loop through the commutator by means of brushes.

6. Make up and write 10 sentences using the words given in the table:

While preparing for an exami­nation

she

they

always studies in the reading-hall.

sed to study in the library.

will work systematically.

When heated to a sufficient high tempera­ture

a body

a steel bar

becomes a source of light.

becomes a source of heat.

While vibrating

a body strings

produces a sound.

will produce a sound.

produced a sound.

109

While measuring a current

the am­meter

is connected in series in the circuit.

can be connected to any part of the circuit.

will be able to be connected to any part of the circuit.

was connected in series in the circuit.