substances – речовини
to resist – чинити опір
insulator – ізолятор
conductance – провідність
passing electric charges – проходячи електричні заряди
water pipe – водопровідна труба
readily – легко
similar material – подібний матеріал
opposition – супротивність, протидія
copper – мідь
to carry - носити
socket – розетка
a piece of string – частина нитки
desk lamp cords and radio cords – шнури настільної лампи чи радіо шнури
II. Read and translate the text.
All substances have some ability of conducting the electric current, however, they differ greatly in the ease with which the current can pass through them. Metals, for example, conduct electricity with ease while rubber does not allow it to flow freely. Thus, we have conductors and insulators.
What do the terms "conductors" and "insulators" mean? Substances through which electricity is easily transmitted are called conductors. Any material that strongly resists the electric current flow is known as an insulator.
Let us first turn our attention to conductance, that is the conductor's ability of passing electric charges. The four factors conductance depends on are: the size of the wire used, its length and temperature as well as the kind of material to be employed.
It is not difficult to understand that a large water pipe can pass more water than a small one. In the same manner, a large conductor will carry the current more readily than a thinner one.
It is quite understandable, too, that to flow through a short conductor is certainly easier for the current than through a long one in spite of their being made of similar material. Hence, the longer the wire, the greater is its opposition, that is resistance, to the passage of current. As mentioned above, there is a great difference in the conducting ability of various substances. For example, almost, all metals are good electric current conductors. Nevertheless copper carries the current more freely than iron; and silver, in its turn, is a better conductor than copper.
Generally speaking, copper is the most widely used conductor. That is why the electrically operated devices in your home are connected to the wall socket by copper wires. Indeed, if you are reading this book by an electric lamp light and somebody pulls the metal wire out of the socket, the light will go out at once. The electricity has not been turned off but it has no path to travel from the socket to your electric lamp. The flowing electrons cannot travel through space and get into an electrically operated device when the circuit is broken. If we use a piece of string instead of a metal wire, we shall also find that the current stops flowing.
A material like string which resists the flow of the electric current is called an insulator.
There are many kinds of insulation used to cover the wires. The kind used depends upon the purposes the wire or cord is meant for. The insulating materials we generally use to cover the wires are rubber, asbestos, glass, plastics and others. Rubber covered with cotton, or rubber alone is the insulating material usually used to cover desk lamp cords and radio cords. Glass is the insulator to be often seen on the poles that carry the telephone wires in city streets. Glass insulator strings are usually suspended from the towers of high voltage transmission lines. One of the almost insulators of all, however, is air. That is why power transmission line wires are bare wires depending on air to keep the current from leaking off.
Conducting materials are by no means the only materials to play an important part in electrical engineering. There must certainly be a conductor, that is a path, along which electricity is to travel and there must be insulators keeping it from leaking off the conductor.
II. Give the Ukrainian equivalents for the words and word combinations below:1) conductors; 2) insulators; 3) transmit; 4) resistance; 5) passage of current; 6) socket; 7) to connect to; 8) cord; 9) high voltage transmission line; 10) leak off.
III. Find in the text the sentences with the following related words and translate them:conducting – conductor – conductivity – conductance
IV. Guess what it is?1. used to cover desk lamp cords
2. one of the most important insulators of all
3. the most widely used conductor
4. a better conductor than copper
5. not so good conductor as copper
6. the insulator usually used on the city street poles and high voltage transmission lines
V. State questions to the underlined words:1) Solid metals conduct electricity with ease.
2) Conductance depends on the four factors.
3) There are many kinds of insulation used to cover the wires.
4) Insulators keep electricity from leaking off the conductor.
5) Conductors play an important role in electrical engineering.
VI. Say whether these sentences are true or false:1) Electrical conductivity of a body depends upon its atomic constitution.
2) There is no difference in the conducting ability of various substances.
3) The longer the wire is the weaker its opposition is.
4) The kind of the insulating material depends upon the purpose it is meant for.
5) Conductors are substances through which electricity is easily transmitted.
6) Insulators do not allow the electric current to flow freely.
VII. Fill in the blanks with the words and phrases:
2. We need ____________for a chemical experiment.
3. When the temperature rises _______to the passing current increases.
4. ______is a perfect insulator.
5. If the switch is __________ the current does not flow.
6. _____is a poor conductor electricity.
7. ________ is a wire not covered with insulated material.
8. We study________.
9. If a wire is covered with_______ it is called an insulated wire.
10. Any magnet has two __________ .
11. Some liquids have ______________ properties.
12. Electricity … by wires.
13. The train ____________ a great distance from Lviv to Sevastopol.
14. If there is no insulation the current can _____ the conductor.
15. We shall consider the ability of insulators _______ the current flow.
16. Copper wires connect electrical devices to the _______________ .
VIII. Arrange the following words in pairs of
1. substance different ease dissimilar
a) Synonyms: b) Antonyms:
2. easily to use difficult to turn off
3. to employ readily short thick
4. various to oppose to turn on insulator
5. to allow of course conductor to close
6. to resist instrument large long
7. certainly to permit thin small
8. device matter like difficulty
9. to break easy
IX. Find the correct variant:
|1. Insulators are materials having||a) low resistance.||b) high resistance.|
|2. Current passes through conductors||a) easily.||b) with great difficulty|
|3. Copper and silver are||a) common conductors.||b) common insulators.|
|4. Air, paper and plastics are||a) common conductors.||b) common insulators.|
|5. Insulators are used||a) to store electric current.||b) to prevent a short between conducting wires.|
|6. Metals increase their resistance||a) when the temperature decreases||b) when the temperature increases.|
|7. In case a high voltage is applied to an insulator||a) it does not conduct current.||b) it conducts current.|
X. Translate the following sentences into English:1. Існує велика різниця в провідній здатності різних матеріалів.
2. Тим не менше мідь проводить струм більш легко, ніж залізо.
3. Існує багато видів ізоляції, що використовується для покриття проводів.
4. Від чого залежить провідність?
5. Чи можемо ми обходитись без ізоляторів?
6. Які матеріали є найкращими провідниками електричної енергії?
7. Які ізолятори ви знаєте?
XI. Find the following words and words combinations in the text.1. проводник ________________
2. изолятор _________________
3. ток проходит _____________
4. медь и серебро ______________
5. сопротивление ______________
6. преимущества _________
7. проволочный проводник __________
8. источник напряжения _____________
9. активная нагрузка ___________________
10. коэфициент ________________________
11. изменение _________________________
12. Углерод __________________________
13. принимать во внимание __________________
14. Увеличивать ___________________________
15. для того, чтобы _______________________
16. увеличивать/ уменьшать _________________