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EXERCISES
A
Notice the correct variant. Remember information technology:
1. a capacitor is used
a) to supply voltage
b) to increase the voltage output
c) to shop energy
2. the main parts of a capacitor are
a) insulators only
b) metal plates just
c) metal plates and insulators between them
three. the part of insulators is
a) to shop energy
b) to isolate the metal plates
c) to prevent a brusk betwixt the metal plates
4. the capacity of a capacitor depends on
a) the size of the plates
b) the distance between the plates
c) the material of the insulators
five. the chapters of a fixed capacitor
a) is abiding
b) is varied
half-dozen. the plates of a variable capacitor
a) can be moved
b) cannot be moved
7. in order to charge a capacitor a voltage source is applied
a) to the metal plates
b) to the insulators
viii. the greater the distance between the plates
a) the greater the capacity of a capacitor
b) the less the capacity
9. variable capacitors have
a) air insulators
b) paper insulators
c) ceramic insulators
10
electrolyte capacitors accept
a) a very depression capacity
b) a very loftier capacity
11. in case a capacitor has a trouble
a) it operates
b) information technology stops operating
B
Cease the sentences using the words with the opposite meaning:
I. The plates of a fixed capacitor cannot be moved to vary the capacity� � . 2. The capacity of a variable capacitor is varied. 3. Electrolyte capacitors modify their capacity when the temperature changes... � . 4. The less the distance between the plates the greater the capacity ... ... . 5. \\'hen a capacitor has no trouble it stores energy � � .
C
Answer the following questions:
I. What is a capacitor used for? 2. What are the master parts of a capacitor? 3. What is the function of insulators? iv. What does the chapters of a capacitor depend on? 5. What is the difference betwixt a fixed capacitor and a variable one? vi. What should be washed in order to change a capacitor? 7. What is the relation between the value of chapters and the altitude of plates? 8. What type of insulators accept variable capacitors? ix. What should be done in case a capacitor has a problem?
������ � �������
A
ii - �; three - b, �; 4 - b; 5 - a; half dozen - a; 7 - a; 8 - b; nine - a; 10 - b; 11 - Jb.
�
1. variable movement
2. fixed does not change
3. paper do non change
4. the greater the less
5. has does not store
C
i. to store electric free energy
2. metal plates and insulators
three. to isolate the metal plates
4. the voltage, the size of plates and their number, the distance between the-plates, material
of insulator
five. stock-still - capacity does not change; variable - changes
half dozen. to alter insulator
7. the greater the altitude the less the capacity
8. air insulators
ix. it should be substituted.
Lesson 8 |
CONDUCTORS AND INSULATORS |
CONDUCTORS |
silvery | widely | |
copper | decrease | |
coefficient | telephone call | |
inexpensive | wire conductors | |
and then that | copper wire conductors | |
Conductors are materials having a depression resistance, so that current easily passes through them. The lower the resistance of the material the more current can pass through it.
The nearly mutual conductors are metals, and argent and copper are the best of them. The reward of copper is that it is much cheaper than silver. Thus copper is widely used to produce wire conductors. One of the common functions of wire conductors is to connect a voltage source to a load resistance. Since copper wire conductors take a very low resistance a minimum voltage drib is produced in them. Thus, all of the applied voltage can produce current in the load resistance.
It should be taken into consideration that nearly materials change the value of resistance when their temperature changes.
Metals increment their resistance when the temperature increases while carbon decreases its resistance when the temperature increases. Thus, metals have a positive temperature coefficient �f resistance while carbon has a negative temperature coefficient. The smaller is the temperature coefficient or the less the change of resistance with the change of temperature, the more perfect is the resistance material.
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������������� �������� ������������� ��� ��������� �����������, � ������������� ���� ������. ����� �������, ������� ����� ������������� ������������� ����������� �������������, � ����� � �������������. ��� ������ ������������� ����������� ��� ������ ��������� ������������� � ���������� �����������, ��� ����� �������� �������������.
EXERCISES
I. Answer the following questions:
I. What is the text about? 2. What materials are called conductors? 3. What is the advantage of copper compared with silverish? 4. What is the most mutual function of wire conductors? 5. Why is a minimum voltage drop produced in copper conductors? six. What is the relation between the value of resistance and the temperature in carbon?
������ � �������
I
1. conductors
ii. with a low resistance
iii. it is much cheaper
four. to connect a voltage source to a load resistance
5. they accept a very low resistance
half-dozen. carbon decreases its resistance when the temperature increases.
INSULATORS
difficulty | brand something do something something |
rubber | |
Materials having a very high resistance are called insu�lators. Current passes through insulators with great diffi�culty.
The most common insulators are air, paper, prophylactic, plastics.
Any insulator can acquit electric current when a high enough voltage is applied to it. Currents of cracking value must exist applied to insulators in order to make them bear. The higher the resistance of an insulator the greater the applied voltage must be.
When an insulator is connected to a voltage source, it stores electric charge and a potential is produced on the insulator. Thus, insulators have the two main functions:
ane. to isolate conducting wires and thus to prevent a curt between them and
two. to store electric charge when a voltage source is ap�plied.
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����� �������� ����� ��������� ��� ��� ���������� ������� ����������� ����������. ����� ������� ��������� ������������, � ��� ������ ���� ��������� ���������� ������� ��������. ��� ���� ������������� ���������, ��� ������� ���������� ������ ���� ���������.
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1. ����������� ���������� �, ����� �������, ������������� �������� ��������� ����� ���� �
2. ����������� ������������� ����� ��� ������� ��������� �������.
EXERCISES
A
Observe the right variant. Call up information technology:
one. insulators are materials having
a) depression resistance
b) high resistance
2. current passes through conductors
a) easily
b) with not bad difficulty
three. copper and silver are
a) common conductors
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