2020-04-07
3860
Lesson 13. Filters
1. Read and learn the words:
filter - фильтр
bypass - шунт
choke - дроссель
high-pass - высокопроходной
low-pass - низкопроходной
to oppose - оказывать сопротивление
on the other hand - с другой стороны
choke coil - дроссельная катушка
bypass coil - шунтовая катушка
bypass condenser - шунтирующий конденсатор
high-pass filter - фильтр верхних частот
low-pass filter - фильтр низких частот
opposing coils - противодействующие витки
opposed current – противоток
Read and translate the text.
Filters
This filter is used to separate direct current from alternating current. It consists of a capacitor and a choke coil. Direct current cannot flow through the capacitor since its insulators oppose the flow of direct current. Therefore, it flows through the choke coil. Its windings easily pass direct current through them. Alternating current, on the other hand, passes through the capacitor, since it cannot easily pass through the choke coil. In this way the direct and the alternating currents are separated.
I. A high-pass filter is used to pass high frequencies and to prevent the flow of low frequencies. It consists of a condenser and an inductance coil. The condenser passes currents of high frequencies and opposes the flow of low frequency currents. Low frequencies must be returned to the source and the inductance coil is used for a bypass.
II. A low-pass filter is used to pass low frequencies and to prevent the flow of high frequencies. It consists of an inductance coil and a condenser. The inductance coil passes low frequencies and opposes the flow of high frequencies. To return the high frequencies back to the source, a condenser is used for a bypass. Its capacity opposes the flow of low frequencies through it.
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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.
4. 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..........
5. 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.
Практическое занятие 14. Электронные лампы
Lesson 14. Electron Tubes
1. Read and learn the words:
tube - электронная лампа
bulb - баллон
grid - сетка
screen - экран
to contain - вмещать
to collect - собирать
to emit - излучать
to suppress - глушить, подавлять
control circuit - контрольная цепь
control grid - управляющая сетка
screen grid - экранирующая сетка
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screen grid tube - экранированная лампа
suppressor grid - защитная сетка
counter flow - противоток
oscillatory circuit - колебательный контур
Read and translate the text.
Electron Tubes
Let us consider electron tubes. Among the electron tubes in use nowadays there are a diode, a triode, a tetrode and a pentode. The main parts of electron tubes are electrodes. Electrodes are placed into a glass or metal bulb.
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 o f 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.
3. 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.
4. 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?
