Electronics Devices And Circuit 2(TTA)
INSTRUCTIONS-1. NUMBER OF QUESTIONS 25
2. HAS A TIME LIMIT OF 15 MINUTES
3. HAS A PASS MARKS OF 30%
4. QUESTIONS PER PAGE 1
5. EACH QUESTIONS HAS 1 MARKS
6. NEGATIVE MARKING FOR EACH QUESTIONS IS 0.257. WILL ALLOW TO YOU GO BACK ,SKIP AND CHANGE YOUR ANSWERS
8. WILL ALLOW TO YOU PRINT OUT YOUR RESULT AND CERTIFICATE
9. WILL ALLOW TO YOU PRINT OUT YOURS RESPONSE SHEET WITH
CORRECT ANSWER KEY AND EXPLANATION
.
Questions and Answers
- 1.
When a diode is forward-biased, the recombination of free electron and holes may produce
- A.
Heat
- B.
Light
- C.
Radiation
- D.
All of the above
Correct Answer
D. All of the aboveExplanation
When a diode is forward-biased, the recombination of free electrons and holes may produce heat, light, and radiation. This is because when the diode is forward-biased, the positive terminal of the voltage source is connected to the p-side of the diode and the negative terminal is connected to the n-side. This causes the free electrons from the n-side to move towards the p-side and recombine with the holes. This recombination process can result in the release of energy in the form of heat, light, and radiation. Therefore, all of the above options are correct.Rate this question:
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- 2.
A Zener diode is based on the principle of
- A.
Thermionic emission
- B.
Tunneling of charge carriers across the junction
- C.
Diffusion of charge carriers across the junction
- D.
None of the above NONE OF THESE
Correct Answer
B. Tunneling of charge carriers across the junctionExplanation
A Zener diode is based on the principle of tunneling of charge carriers across the junction. This means that the charge carriers are able to pass through the junction barrier, allowing current to flow in the reverse direction. This phenomenon is known as the Zener effect and is utilized in Zener diodes to regulate voltage and provide voltage stabilization.Rate this question:
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- 3.
Silicon diode is less suited for low voltage rectifier operation because
- A.
Its breakdown voltage is high
- B.
Its reverse saturation current is low
- C.
Its cut-in voltage is high
- D.
None of the above
Correct Answer
C. Its cut-in voltage is highExplanation
A silicon diode is less suited for low voltage rectifier operation because its cut-in voltage is high. The cut-in voltage is the minimum voltage required for the diode to start conducting current in the forward direction. In low voltage applications, such as rectification, a lower cut-in voltage is desirable as it allows for more efficient and effective operation. A high cut-in voltage in a silicon diode would result in a higher voltage drop and potentially inefficient rectification.Rate this question:
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- 4.
Silicon is not suitable for fabrication of light-emitting diodes because it is
- A.
An indirect band gap semiconductor
- B.
A direct band gap semiconductor
- C.
A wide band gap semiconductor
- D.
None of the above
Correct Answer
A. An indirect band gap semiconductorExplanation
Silicon is not suitable for the fabrication of light-emitting diodes because it is an indirect band gap semiconductor. In an indirect band gap semiconductor, the minimum energy required for an electron to transition from the valence band to the conduction band is not efficiently emitted as light. This means that the recombination of electrons and holes does not result in the emission of photons, which is necessary for the functioning of a light-emitting diode. Therefore, silicon, being an indirect band gap semiconductor, is not suitable for the fabrication of LEDs.Rate this question:
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- 5.
A Zener diode
- A.
Has a high forward voltage rating
- B.
Has a sharp breakdown at low reverse voltage
- C.
Is useful as an amplifier
- D.
None of the above
Correct Answer
B. Has a sharp breakdown at low reverse voltageExplanation
A Zener diode is a type of diode that has a sharp breakdown at low reverse voltage. This means that when the reverse voltage across the diode exceeds a certain threshold, called the Zener voltage, the diode starts conducting current in the reverse direction. This characteristic makes Zener diodes useful for voltage regulation and protection against voltage spikes. The other options, such as having a high forward voltage rating or being useful as an amplifier, do not accurately describe the behavior of a Zener diode.Rate this question:
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- 6.
Which of these is a best description of a Zener diode?
- A.
It operates in the reverse region
- B.
It is a constant voltage device
- C.
It is a constant current device
- D.
All of the above
Correct Answer
B. It is a constant voltage deviceExplanation
A Zener diode is a type of diode that operates in the reverse region, meaning that it conducts current when the voltage across it is in the reverse direction. It is commonly used as a voltage regulator, maintaining a constant voltage across its terminals even when the input voltage varies. Therefore, it can be described as a constant voltage device. It does not function as a constant current device, so the correct answer is that it is a constant voltage device.Rate this question:
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- 7.
When two Zener diodes each of 10 V and 15 V are connected in series, then the overall voltage between them when they are in conduction is
- A.
10 V
- B.
25 V
- C.
15 V
- D.
Zero
Correct Answer
C. 15 VExplanation
When two Zener diodes are connected in series, the overall voltage between them when they are in conduction is equal to the sum of their individual voltages. In this case, since the Zener diodes have voltages of 10 V and 15 V respectively, the overall voltage between them would be 10 V + 15 V = 25 V. Therefore, the correct answer is 25 V.Rate this question:
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- 8.
The LED is usually made of materials like
- A.
GaAs
- B.
C and Si
- C.
GeAs
- D.
None of these
Correct Answer
A. GaAsExplanation
The LED (Light Emitting Diode) is usually made of materials like GaAs (Gallium Arsenide). GaAs is a commonly used semiconductor material in LED manufacturing due to its high efficiency and ability to emit light in the visible spectrum. C (Carbon) and Si (Silicon) are not typically used in LED production, and GeAs (Germanium Arsenide) is also not commonly used. Therefore, the correct answer is GaAs.Rate this question:
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- 9.
Varactor diodes are used in FM receivers to obtain
- A.
Automatic frequency control
- B.
Automatic gain control
- C.
Automatic volume control
- D.
None of the above
Correct Answer
A. Automatic frequency controlExplanation
Varactor diodes are used in FM receivers to obtain automatic frequency control. This is because varactor diodes have a variable capacitance that can be controlled by changing the reverse bias voltage applied to them. By varying the capacitance, the resonant frequency of the tuned circuit can be adjusted, allowing for automatic frequency control in FM receivers. Automatic gain control and automatic volume control are not directly related to the use of varactor diodes in FM receivers.Rate this question:
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- 10.
.No-load voltage of power supply is 100 V and full-load voltage is 80 V, the percentage of regulation is
- A.
0
- B.
25
- C.
15.75
- D.
None of above
Correct Answer
B. 25Explanation
The percentage of regulation is calculated by subtracting the full-load voltage from the no-load voltage, dividing the result by the full-load voltage, and then multiplying by 100. In this case, the calculation would be (100 - 80) / 80 * 100 = 25. Therefore, the percentage of regulation is 25%.Rate this question:
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- 11.
Zener diodes are used as
- A.
Reference voltage elements
- B.
Reference current elements
- C.
Reference resistance
- D.
None of these
Correct Answer
A. Reference voltage elementsExplanation
Zener diodes are used as reference voltage elements because they have a specific breakdown voltage known as the Zener voltage. When the voltage across the diode exceeds this Zener voltage, it starts conducting in the reverse direction, maintaining a constant voltage regardless of the current flowing through it. This characteristic makes Zener diodes suitable for generating stable and accurate reference voltages in electronic circuits.Rate this question:
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- 12.
Zener diodes are
- A.
Specially doped p-n junctions
- B.
Normally doped p-n junctions
- C.
Lightly doped p-n junctions
- D.
None of the above
Correct Answer
A. Specially doped p-n junctionsExplanation
Zener diodes are specially doped p-n junctions. This means that the p and n regions of the diode are intentionally doped with impurities to create a specific level of doping concentration. This special doping allows the diode to exhibit the Zener effect, which is the ability to conduct current in reverse bias and maintain a nearly constant voltage across the diode. This makes Zener diodes useful for voltage regulation and protection in electronic circuits.Rate this question:
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- 13.
A general propose diode is more likely to suffer an avalanche breakdown rather than a Zener breakdown because
- A.
It is lightly doped
- B.
It is heavily doped
- C.
It has weak covalent bonds
- D.
None of the above
Correct Answer
A. It is lightly dopedExplanation
A general purpose diode is more likely to suffer an avalanche breakdown rather than a Zener breakdown because it is lightly doped. Avalanche breakdown occurs when the electric field across the diode is high enough to cause the generation of electron-hole pairs through collision, leading to a sudden increase in current. Lightly doped diodes have a lower breakdown voltage, making them more susceptible to avalanche breakdown. On the other hand, Zener breakdown occurs in heavily doped diodes when the electric field is high enough to cause the tunneling of electrons across the depletion region.Rate this question:
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- 14.
Zener diode
- A.
Has a high forward voltage rating
- B.
Is useful as an amplifier
- C.
Has a sharp breakdown at low reverse voltage
- D.
None of the above
Correct Answer
C. Has a sharp breakdown at low reverse voltageExplanation
A Zener diode is a type of diode that is designed to operate in the reverse breakdown region. It has a sharp breakdown at low reverse voltage, meaning that it starts conducting significantly when the reverse voltage across it reaches a certain threshold. This characteristic makes it useful for voltage regulation and protection in electronic circuits. The other options mentioned, such as having a high forward voltage rating or being useful as an amplifier, do not accurately describe the behavior and characteristics of a Zener diode.Rate this question:
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- 15.
.If the junction temperature of LED is increased the radiant output power
- A.
Decreases
- B.
Increases
- C.
Remains the same
- D.
None of the above none of these
Correct Answer
A. DecreasesExplanation
When the junction temperature of an LED increases, the radiant output power decreases. This is because as the temperature rises, the efficiency of the LED decreases, causing it to emit less light. The increase in temperature can also lead to thermal degradation of the LED, further reducing its radiant output power. Therefore, the correct answer is "Decreases".Rate this question:
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- 16.
The Zener effect is valid approximately
- A.
Below 5 V
- B.
Above 5 V
- C.
Equal to 5 V
- D.
None of the above
Correct Answer
A. Below 5 VExplanation
The Zener effect is a phenomenon observed in a Zener diode, where it exhibits a sharp increase in current when the voltage across it reaches a certain threshold called the Zener voltage. This effect is valid below 5 V, meaning that when the voltage across the Zener diode is less than 5 V, it will not exhibit the Zener effect.Rate this question:
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- 17.
.The clipping action of a diode requires that its forward resistance
- A.
Be zero
- B.
Have a finite value
- C.
Be infinite
- D.
None of the above none of these
Correct Answer
A. Be zeroExplanation
The clipping action of a diode requires that its forward resistance be zero. This means that when the diode is forward biased, it should ideally have no resistance, allowing current to flow through it without any hindrance. This is necessary for the diode to effectively clip or limit the voltage or current in a circuit. If the forward resistance of the diode is not zero, it will impede the flow of current and the clipping action will not be achieved.Rate this question:
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- 18.
For a low voltage rectification
- A.
Two diode full-wave rectifier is suitable
- B.
Both bridge and full-wave rectifier are suitable
- C.
Bridge rectifier is suitable
- D.
None of the above none of these
Correct Answer
A. Two diode full-wave rectifier is suitableExplanation
A two diode full-wave rectifier is suitable for low voltage rectification because it allows for the conversion of AC voltage into DC voltage. In a two diode full-wave rectifier, both positive and negative halves of the AC waveform are rectified, resulting in a smoother DC output compared to a half-wave rectifier. This makes it a suitable choice for low voltage applications where a more stable DC output is desired. A bridge rectifier, on the other hand, is typically used for higher voltage applications.Rate this question:
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- 19.
If Vm is the peak value of an applied voltage in a half-wave rectifier with a large capacitor across the load, then PIV is
- A.
Vm
- B.
Vm/2
- C.
2Vm
- D.
None of these
Correct Answer
C. 2VmExplanation
In a half-wave rectifier with a large capacitor across the load, the peak inverse voltage (PIV) is the maximum voltage that the diode must withstand when it is reverse-biased. Since the capacitor charges to the peak value of the applied voltage, the reverse voltage across the diode is twice the peak value of the applied voltage. Therefore, the correct answer is 2Vm.Rate this question:
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- 20.
.The most significant component of ripple voltage in a half-wave rectifier is contained in
- A.
Fundamental frequency
- B.
Second harmonic
- C.
DC component
- D.
None of the above none of these
Correct Answer
A. Fundamental frequencyExplanation
The most significant component of ripple voltage in a half-wave rectifier is contained in the fundamental frequency. This is because in a half-wave rectifier, only half of the input waveform is rectified, resulting in a pulsating DC output. The ripple voltage is caused by the variation in the rectified voltage as the AC input signal changes polarity. The fundamental frequency represents the lowest frequency component of the AC input signal, and therefore, it contributes the most to the ripple voltage. The second harmonic, DC component, and none of the above do not play a significant role in the ripple voltage of a half-wave rectifier.Rate this question:
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- 21.
The disadvantages of capacitor input LC filter are
- A.
High cost, more weight and external field produced by a series inductor
- B.
High cost, less weight
- C.
Low cost, more weight
- D.
None of these
Correct Answer
A. High cost, more weight and external field produced by a series inductorExplanation
The disadvantages of a capacitor input LC filter include high cost, more weight, and the external field produced by a series inductor. This means that the filter can be expensive to implement, adds additional weight to the system, and may produce electromagnetic interference due to the presence of the series inductor.Rate this question:
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- 22.
Larger the value of the capacitor filter
- A.
Smaller the dc voltage across the load
- B.
Longer the time that current pulse flows through the diode
- C.
Larger the peak current in the rectifying diode
- D.
None
Correct Answer
C. Larger the peak current in the rectifying diodeExplanation
The larger the value of the capacitor filter, the smoother the output voltage across the load. This means that the fluctuations in the voltage are reduced, resulting in a more constant voltage across the load. As a result, the current flowing through the diode will also be more constant, leading to a larger peak current in the rectifying diode.Rate this question:
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- 23.
Which rectifier requires four diodes?
- A.
Half-wave voltage doubler
- B.
Full-wave voltage doubler
- C.
Full-wave bridge circuit
- D.
None of the above
Correct Answer
A. Half-wave voltage doublerExplanation
A half-wave voltage doubler requires four diodes because it uses a combination of two diodes to rectify the positive half-cycle of the input voltage and another two diodes to rectify the negative half-cycle. By using this configuration, the voltage across the load is doubled compared to a regular half-wave rectifier.Rate this question:
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- 24.
Diode transition or space capacitance is due to
- A.
Majority carrier moves from junction
- B.
Storage of minority charge
- C.
Both
- D.
None of these
Correct Answer
A. Majority carrier moves from junctionExplanation
The diode transition or space capacitance is due to the majority carrier moving from the junction. This movement of majority carriers creates a capacitance effect in the diode, which affects its overall behavior. The storage of minority charge, on the other hand, is not directly related to the diode transition or space capacitance.Rate this question:
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- 25.
Which circuit of transistor is known as emitter follower
- A.
CB
- B.
CC
- C.
CE
- D.
ALL
Correct Answer
B. CCExplanation
The circuit of transistor known as an emitter follower is the Common Collector (CC) configuration. In this configuration, the emitter terminal is connected directly to the output, while the collector terminal is connected to the supply voltage through a resistor. The CC configuration provides a high input impedance and a low output impedance, making it suitable for impedance matching and voltage amplification applications.Rate this question:
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