CHAPTER # 16
BASIC ELECTRONICS
Multiple Choice Questions
i.
Thermionic Emission
ii.
Electrons
iii.
NAND
iv.
NAND gates
v.
Both A and B are 0
vi.
A and B are 1
vii.
Both of its input is 1
REVIEW QUESTIONS
16.1 What happens when a narrow beam of electrons is passed through (a) a uniform electric field (b) a uniform magnetic field. What do these results indicate about the charge on electron?
When a narrow beam of electrons is passed through a uniform electric field it will deflect towards positive plate. When it is passing through a uniform magnetic field it will deflect from its original path. These results indicate that the charge on electron is negative.
16.2 Explain the working of different parts of oscilloscope.
Oscilloscope consists of mainly three parts.
- Electron gun
- Deflecting plates
- Fluorescent screen
For long Question Refer to PTB (Punjab Text Book) page # 142, topic 16.3.
16.3 Name some uses of oscilloscope.
- It is used to display waveforms.
- It is used to measure Voltage.
- It is used in radar.
- It is used in echo-sounding.
- It is used to display heartbeats.
16.4 Explain the following.
a) How the filament is heated?
A 6-volt supply is connected with the filament to heat it.
b) Why the filament is heated?
To obtain a fine beam of electrons, filament is heated.
c) Why the anode potential is kept positive with respect to the cathode potential?
The positive potential of an anode is used to accelerate electrons emitted from a heated filament. As the electrons pass through the anode, they are focused into a fine beam.
d) Why a large potential is applied between anode and cathode?
A large potential is applied between anode and cathode to direct the electrons in specific direction.
e) Why the tube is evacuated?
Ionization of gases in the tube occurs as a result of the high voltage applied across the tube, so it must be evacuated. Because of gas ionization, a fine beam of electrons cannot be produced and accelerated in a specific direction.
16.5 What is electron gun? Describe the process of thermionic emission.
To investigate the properties of an electron beam, an electron gun is used. It consists of a tungsten filament with 6-volt supply and a high voltage supply.
For long Question Refer to PTB (Punjab Text Book) page # 141, topic 16.2.
16.6 What do you understand by digital and analogue quantities?
|
Analogue
Quantity |
Digital
Quantity |
|
Analogue
quantities are those that change over time in a continuous manner. |
Quantities that
change in discrete steps are referred to as digital quantities. |
16.7 Differentiate between analogue electronics and digital electronics. Also write the names of both electronic and analogue devises.
|
Analogue
Electronics |
Digital
Electronics |
|
Analogue
electronics refers to the branch of electronics that processes data in the
form of analogue quantities. |
Digital
electronics is the branch of electronics that processes data that is provided
in the form of digits. |
|
Analogue
Devices |
Digital
Devices |
|
|
16.8 State and explain for each case whether the information given by the following devices is in analogue or a digital form.
a) A moving-coil voltmeter measuring the e.m.f of a cell.
- Analogue form
b) a microphone generating an electric current.
- Analogue form
c) a central heating thermostat controlling the water pump.
- Analogue signal
d) automatic traffic lights controlling the flow of traffic.
- Analogue quantity
16.9 Write down some benefits of using digital electronics over analogue electronics.
- Digital signals are less affected by distortion, noise, and interference.
- Digital circuits are more dependable.
- Digital circuits are easier to design and less expensive than analogue circuits.
- The hardware implementation in digital circuits is more flexible than analogue.
- Cross-talk is extremely uncommon in digital communication.
16.10 What are the three universal Logic Gates? Give their symbols and truth tables.
AND gate
|
A |
B |
X = A.B |
|
0 |
1 |
0 |
|
1 |
0 |
0 |
|
0 |
0 |
0 |
|
1 |
1 |
1 |
OR gate
|
A |
B |
X = A+B |
|
0 |
1 |
1 |
|
1 |
0 |
1 |
|
0 |
0 |
0 |
|
1 |
1 |
1 |
NOT gate
|
A |
X |
|
0 |
1 |
|
1 |
0 |
CONCEPTUAL QUESTION
16.1 Name two factors which can enhance thermionic emission.
- Nature of material
- Temperature
- Surface Area
16.2 Give three reasons to support the evidence that cathode rays are negatively charged electrons.
- Attraction towards positive charge.
- Deflection opposite to positive charge in a magnetic field.
- Its charge to mass ratio is equal to electrons e/m ratio.
16.3 When electrons pass through two parallel plates having opposite charges, they are deflected towards the positively charged plate. What important characteristic of the electron can be inferred from this?
Electrons carry negative charge due to this reason they deflect from positive charge plate in opposite direction.
16.4 When a moving electron enters the magnetic field, it is deflected from its straight path. Name two factors which can enhance electron deflection.
- Speed of electron.
- Strength of magnetic field.
16.5 How can you compare the logic operation X=A.B with usual operation of multiplication?
Whenever we multiply this operation with any Boolean variable, its result is zero. So, it behaves as a multiplicative inverse. Hence, the logic operation (.) is act as an operation of multiplication.
16.6 NAND gate is the reciprocal of AND gate. Discuss
NAND gate is the reciprocal of AND gate because every time the output of AND gate is inverted by Not operation.
16.7 Show that the circuit given below acts as OR gate.
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