Практическое занятие 6. Гальванические элементы

Lesson 6. Electric Cells

1. Read and learn the words:

Cell - элемент

output - емкость, мощность

bulb - электрическая лампа

to light - зажигать, освещать

to increase - увеличиваться), возрастать

to substitute - заменять

...and so on - и так далее

 

Read and translate the text.

 

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. In case a cell has a trouble it stops operating or operates badly. This cell should be substituted by another one.

 

 

3. 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.

 

4. 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?

 

Практическое занятие 7. Конденсаторы

Lesson 7. Capacitors

1. Read and learn the words:

capacitor - конденсатор

insulator - изолятор

frequency -  частота

distance -  расстояние

advantage - преимущество

disadvantage -  недостаток

plate - анод (лампы)

part - часть

to apply - прилагать, применять

to move - двигать(ся)

to prevent -  предотвращать

reason - причина

for this reason - по этой причине

besides - кроме того

provided that - при условии что

Read and translate the text.

Capacitors

A capacitor is one of the main elements of a circuit. It is used to store  electric energy. A capacitor stores electric energy provided that a voltage source is applied to it.

The main parts o f a capacitor are metal plates and insulators. The function of insulators is to isolate the metal plates and in this way to prevent a short.

In the diagram one can see two common types of capacitors in use nowadays: a fixed capacitor and a variable one. The plates of a fixed capacitor cannot be moved; for this reason its capacity does not change. The plates of a variable capacitor move; its capacity changes. The greater the distance between the plates, the less is the capacity of a capacitor. Variable capacitors are commonly used by radiomen; their function is to vary the frequency in the circuit.

Fixed capacitors are used in telephone and radio work. Fixed capacitors have insulators produced of paper,   ceramics and other materials; variable capacitors have air insulators. Paper capacitors are commonly used in radio and electronics; their advantage is their high capacity: it may be higher than 1,000 picofarad.

Besides, electrolyte capacitors are highly in use. They also have a very high capacity: it varies from 0.5 to 2,000 microfarad. Their disadvantage is that they change their capacity when the temperature changes. They can operate without a change only at temperatures not lower than -40° С.

Common troubles in capacitors are an open and a short. A capacitor stops operating and does not store energy in case it has a trouble. A capacitor with a trouble should be substituted by a new one.

 

 

 

 

3. Complete these sentences using the correct variant:

1. A capacitor is used

a) to supply voltage.

b) to increase the voltage output.

c) to store energy.

 

2. The main parts of a capacitor are

a) insulators only.

b) metal plates only.

c) metal plates and insulators between them.

 

1. The function of insulators is

a) to store energy.

b) to isolate the metal plates.

c) to prevent a short between 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.

 

5. The capacity of a fixed capacitor

a) is constant.

b) is varied.

 

6. The plates of a variable capacitor

a) can be moved.

b) cannot be moved.

 

1. In order to charge a capacitor a voltage source is applied

a) to the metal plates.

b) to the insulators.

 

8. The greater the distance between the plates,

a) the greater is the capacity of a capacitor.

b) the less is the capacity.

 

9. Variable capacitors have

 a) air insulators.

b) paper insulators.

c) ceramic insulators.

 

10. Electrolyte capacitors have

 a) а very low capacity.

b) a very high capacity.

 

11. In case a capacitor has a trouble

a) it operates.

b) it stops operating.