Complete the sentences using the correct variant

1. A filter is used in order	a) to separate d.c. from a.c. b) to transfer energy from the primary to the secondary. c) to separate low frequencies from high frequencies.
2. A filter consists of	a) a resistor and a transformer. b) a choke coil and a capacitor. c) an inductance coil and a capacitor.
3. Direct current easily passes	a) through a choke coil. b) through a capacitor.
4. Alternating current easily passes	a) through a capacitor. b) through a choke coil.
5. A low-pass filter is used	a) to pass high frequencies and to prevent the flow of low frequencies. b) to pass low frequencies and to prevent the flow of high frequencies.
6. In a low-pass filter	a) a capacitor is used as a bypass. b) an inductance coil is used as a bypass.
7. In a high-pass filter	a) an inductance coil is used as a bypass. b) a capacitor is used as a bypass.

3.Complete these sentences using on the other hand. Follow the model.

Model: Direct current passes through the choke coil of a filter; alternating current, on the other hand, passes through the capacitor.

1.A low -pass filter is used to pass low frequencies ….

2.In a high -pass filter an inductance coil is used as a bypass ….

3.A high -pass filter is used to prevent the flow of low frequencies ….

4. Alternating current passes through a capacitor ….     

 

4. Answer the following questions:

1.What is a filter used for?

2.What does a filter consist of?

3.What is the function of a low-pass filter?

4.What is the function of a high-pass filter?

5.What is the difference between a low-pass filter and a high-pass filter?

6.What elements are used as a bypass?

7.What is the function of a choke coil?

8.What is the function of an inductance coil?

 

Draw schemes of a choke input filter and a capacity input filter. Describe the schemes and the function of the filters.

 

Read the text and answer the question that follows it.

Choke Input Filter and Capacity Input Filter

rectify	[ˈrektɪfaɪ]	выпрямить
eliminate	[ɪˈlɪmɪneɪt]	устранить

 

A choke input filter and a capacity input filter are used in rectifiers. Filters of this kind are connected to rectifiers in order to eliminate pulsations produced in rectified current.

1) Choke input filter is a low-pass filter. A choke coil is in series with the rectifier output.

2) Capacity input filter is a high-pass filter. A capacitor is connected directly across or in parallel with the rectifier output.

 

What is the difference between a choke input filter and a capacity input filter?

Unit Seventeen [17]

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 theRussian words back into English.

tube	[tjuːb]	электронная лампа
bulb	[bʌlb]	баллон
grid		сетка
screen		экран
to contain	[kənˈteɪn]	вмещать
to collect	[kəˈlekt]	собирать
to emit	[ɪˈmɪt]	излучать
to suppress	[səˈpres]	глушить, подавлять
control circuit		контрольная цепь
control grid		управляющая сетка
screen grid		экранирующая сетка
screen grid tube		экранированная лампа
suppressor grid		защитная сетка
counter flow		противоток
oscillatory circuit		колебательный контур

 

2. Form nouns adding -er and translate them.

Model: to heat - heater

to emit -	_______________________________________
to control -	_______________________________________
to suppress -	_______________________________________

                  

Distribute the words below into the three columns.

Model:	action	process	doer
	emit	emission	emitter

 

collector, heat, collection, suppress, collect, suppressor, suppression, contain, reaction, container, react, heater, reactor, computer, compute, oscillate, oscillating, oscillator

 

Read the words and put down their Russian equivalents. Then translate them back into English.

diode	[daɪəd]	___________	cathode	[ˈkæθoud]	___________
triode	[traɪəd]	___________	metal	[ˈmetl]	___________
tetrode	[tetˈroud]	___________	glass	[ɡlɑːs]	___________
pentode	[penˈtoud]	___________	oscillator	[ˈɔsɪleɪtə]	___________

Electron Tubes

Let us consider electron tubes. Among the electron tubes in usenowadays there are a diode, a triode, a tetrode and a pentode. The mainparts of electron tubes are electrodes. Electrodes are placed into a glass or metal bulb.

Fig. 14

A diode contains the cathode and the plate. When a diode operates the cathode emits electrons, the plate collects them.

A triode contains the cathode, the plate and the control grid. When the tube operates the cathode emits electrons, the plate collects them and the grid controls the flow of electrons. Therefore, the grid is called a control grid.

A tetrode contains the cathode, the plate, the control grid and the screen grid.

When a tube operates it may oscillate. The function of the screen grid is to eliminate oscillations. Therefore it is called a screen grid.

A pentode contains two electrodes and three grids: the control grid, the screen grid and the suppressor grid. When a pentode operates the suppressor grid eliminates the secondary emission.

Common troubles in tubes are an open heater and low emission. These troubles result from constant use or from some other reason. In case a tube has a trouble it stops operating or operates badly. A tube with a trouble should be replaced by another one.

 

5. Complete the sentences using the correct variant:

1. A pentode contains	a) the cathode, the plate, two screen grids and the suppressor grid. b) the cathode, the plate, the control grids, the screen grid and the suppressor grid.
2. A tetrode contains	a) the cathode, the plate, the suppressor grid and the screen grid. b) the cathode, the plate, the screen grid and the control grid.
3. A triode contains	a) the cathode, the plate and the screen grid. b) the cathode, the plate and the control grid.
4. The function of the cathode is	a) to collect electrons. b) to eliminate the secondary emission. c) to emit electrons.
5. The function of the plate is	a) to eliminate oscillations. b) to emit electrons. c) to collect electrons.
6. The function of the control grid is	a) to emit electrons. b) to control the electron flow. c) to eliminate secondary emission.
7. The function of the screen grid is	a) to collect electrons. b) to reduce the capacity. c) to eliminate oscillations.
8. The function of the suppressor grid is	a) to control the electron flow. b) to eliminate secondary emission. c) to eliminate oscillations.
9. Constant use of a tube results in	a) high emission. b) low emission. c) an open heater.

6. Answer the following questions:

1. What types of electron tubes are used nowadays?

2. How many electrodes does a diode (a triode, a tetrode, a pentode) contain?

3. What is the function of the cathode (the plate, the control grid, the screen grid, the suppressor grid)?

4. What does the constant use of a tube result in?

5. What does low emission result from?

6. When must a tube be replaced?