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6. Complete the sentences using while. Follow the model on page 13.
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6. Complete the sentences using while. Follow the model on page 13.
1. The value of a fixed resistor is constant ….
2. Current-carrying capacity is given in amperes ….
3. The lower the value of current, the lower is the temperature of a resistor ….
4. An electric source produces energy ….
7. Pair work. Put these questions to your groupmate and let him/her answer them.
1. What is a resistor used for?
2. When does the temperature of a resistor rise?
3. What element is used to change the value of voltage?
4. How are resistors rated?
5. What types of resistors do you know?
6. When does a resistor get open?
7. What does an open resistor result in?
8. What is the difference between a fixed resistor and a variable resistor?
9. How much is the current-carrying capacity of a two-ohm resistor?
10. What resistors have a variable value?
8. Solve the problem:
What is the maximum current for a resistor having a 5-watt capacity and a resistance of 20, 000 ohms?
9. Pair work. Think of three similar problems of your own. Ask your groupmate to solve them.
Unit Nine [9]
1. a) Cover the right column and read the English words. Translate them into Russian and check your translation.
b) Cover the left column and translate the Russian words back into English.
| cell | [sel] | элемент |
| output | [ˈ autput] | емкость, мощность |
| bulb | [bʌ lb] | электрическая лампа |
| to light | [laɪ t] | зажигать, освещать |
| to increase | [ɪ nˈ kriː s] | увеличивать(ся), возрастать |
| to substitute | заменять | |
| ... and so on | и так далее |
2. Read the words and put down their Russian equivalents:
| [ɪ ˈ lektroud] | electrode | ___________________________ |
| [ɪ ˈ lektrə laɪ t] | electrolyte | ___________________________ |
| [stɑ ː t] | start | ___________________________ |
| [ˈ ɔ pə reɪ t] | to operate | ___________________________ |
| [ˈ aɪ sə leɪ t] | to isolate | ___________________________ |
3. Translate into Russian and put down the Russian equivalents. Then translate the Russian equivalents back into English (orally).
| a. current capacity | ______________________________ |
| resistor temperature | ______________________________ |
| voltage output | ______________________________ |
| current value | ______________________________ |
| b. to start supplying energy | ______________________________ |
| to stop operating | ______________________________ |
| to start lightening | ______________________________ |
| to stop lightening the bulbs | ______________________________ |
| c. to operate well | ______________________________ |
| to operate badly | ______________________________ |
| to increase the voltage output | ______________________________ |
| to substitute the resistor | ______________________________ |
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4. Read and translate into Russian. Mind one:
1. The element has a trouble. It operates badly. It should be substituted by a new one.
2. The element with a trouble was substituted with a new one and the cell started operating.
Electric Cells
An electric cell is used to produce and supply electric energy. It consists of an electrolyte and two electrodes. Electrodes are used as terminals, they connect the cell to the circuit - current passes through the terminals and the bulb lights.
Cells can be connected in series, in parallel and in series-parallel. In order to increase the current capacity cells should be connected in parallel. In order to increase the voltage output cells should be connected in series. In case a battery has a large current capacity and a large voltage output, its cells are connected in series-parallel.
When cells are connected in series the positive terminal of one cell is connected to the negative terminal of the second cell, the positive terminal of the second cell - to the negative terminal of the third... and so on.
When cells are connected in parallel their negative terminals are connected together and their positive terminals are also connected.
Fig. 6 Fig. 7
In case a cell has a trouble it stops operating or operates badly. This cell should be substituted by another one.
5. Complete the sentences using the correct variant:
| 1. A cell is used | a) to increase the voltage output. b) to reduce the current capacity. c) to supply electric energy. |
| 2. The terminals of a cell are used | a) to conduct current. b) to increase voltage. c) to connect the battery to a circuit. |
| 3. When cells are connected in series | a) all the positive terminals are connected together. b) all the negative terminals are connected together. c) the positive terminal of one cell is connected to the negative terminal of the second. |
| 4. Cells are connected in series in order | a) to increase the current capacity. b) to increase the voltage output. |
| 5. In order to increase the current capacity | a) cells are connected in series, b) cells are connected in parallel. |
6. Answer the following questions:
1. What is a cell used for?
2. What does a cell consist of?
3. What is the function of the terminals?
4. In what way are cells connected in order to increase the voltage output?
5. In what way are cells connected in order to increase the current capacity?
6. In what way are the terminals of series cells connected?
7. In what case does a cell stop operating?
8. What should be done in case it stops operating?
7. Solve these problems:
1. Suppose that you have four electric cells. The current capacity of each cell equals l. 5 amp, the voltage output equals 2 V.
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a) Connect the cells in series. In what way should it be done?
b) Connect the battery to a circuit whose resistance value equals 15 ohms. What is the value of current in the circuit?
2. Suppose that you have three cells of the same value.
a) Connect them in parallel. In what way should it be done?
b) Connect the second battery to the same circuit: what will it result in?
Suppose that one of the cells stops operating. What should be done in this case?
Unit Ten [10]
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