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PN Junction Diode Full Class ( Hindi Version )

Multiple Choice Questions & Notes

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Chapter-1 ( Semiconductor Physics & PN Junction Diode )

Here are 50 multiple-choice questions (MCQs) on Semiconductor Physics and PN Junction Diodes, along with the answers:

1. What is the basic difference between conductors, semiconductors, and insulators?

• a) Number of electrons
• b) Energy band gap
• c) Type of atoms
• d) Number of protons
  Answer: b) Energy band gap

2. Which of the following materials is a semiconductor?

• a) Copper
• b) Silicon
• c) Iron
• d) Rubber
  Answer: b) Silicon

3. In intrinsic semiconductors, the number of free electrons is equal to the number of:

• a) Holes
• b) Protons
• c) Neutrons
• d) Ions
  Answer: a) Holes

4. The energy gap of Silicon at room temperature is approximately:

• a) 1.1 eV
• b) 2.2 eV
• c) 0.7 eV
• d) 1.5 eV
  Answer: a) 1.1 eV

5. In a PN junction diode, the P side is called the:

• a) Cathode
• b) Anode
• c) Gate
• d) Collector
  Answer: b) Anode

6. What happens at the depletion region in a PN junction diode?

• a) It conducts electricity freely.
• b) It becomes completely insulating.
• c) Electrons and holes recombine.
• d) Only holes move freely.
  Answer: c) Electrons and holes recombine.

7. Which of the following is a majority carrier in the N-type semiconductor?

• a) Electrons
• b) Holes
• c) Neutrons
• d) Protons
  Answer: a) Electrons

8. A diode is forward biased when:

• a) The P side is connected to the negative terminal of the battery.
• b) The N side is connected to the positive terminal of the battery.
• c) The P side is connected to the positive terminal of the battery.
• d) The P side is connected to ground.
  Answer: c) The P side is connected to the positive terminal of the battery.

9. The potential barrier in a silicon diode is approximately:

• a) 0.3 V
• b) 0.7 V
• c) 1.1 V
• d) 1.5 V
  Answer: b) 0.7 V

10. What happens to the width of the depletion region when a PN junction is reverse biased?

• a) It increases.
• b) It decreases.
• c) It remains the same.
• d) It disappears.
  Answer: a) It increases.

11. In which type of material is the Fermi level exactly in the middle of the band gap?

• a) Intrinsic semiconductor
• b) Extrinsic semiconductor
• c) Conductor
• d) Insulator
  Answer: a) Intrinsic semiconductor

12. What is the main purpose of doping in semiconductors?

• a) To increase the number of free electrons.
• b) To decrease the energy band gap.
• c) To create a depletion region.
• d) To make the material a better insulator.
  Answer: a) To increase the number of free electrons.

13. The reverse saturation current in a PN junction diode is:

• a) Directly proportional to temperature
• b) Inversely proportional to temperature
• c) Independent of temperature
• d) None of the above
  Answer: a) Directly proportional to temperature

14. When a diode is reverse biased, the current through the diode is:

• a) High
• b) Low
• c) Zero
• d) None of the above
  Answer: b) Low

15. The majority carriers in a P-type semiconductor are:

• a) Electrons
• b) Holes
• c) Neutrons
• d) Protons
  Answer: b) Holes

16. Zener diodes are designed to operate in which region?

• a) Forward bias
• b) Reverse bias
• c) Forward breakdown
• d) None of the above
  Answer: b) Reverse bias

17. Which process leads to the formation of an N-type semiconductor?

• a) Doping with pentavalent impurities
• b) Doping with trivalent impurities
• c) Heating the semiconductor
• d) Cooling the semiconductor
  Answer: a) Doping with pentavalent impurities

18. In a diode, if the anode is at a higher potential than the cathode, the diode is:

• a) Reverse biased
• b) Forward biased
• c) Open circuited
• d) Short circuited
  Answer: b) Forward biased

19. The term “extrinsic semiconductor” refers to:

• a) Pure semiconductor material
• b) Semiconductor material with added impurities
• c) Non-conducting material
• d) Conducting material
  Answer: b) Semiconductor material with added impurities

20. The main application of a Zener diode is:

• a) Rectification
• b) Voltage regulation
• c) Signal amplification
• d) Frequency modulation
  Answer: b) Voltage regulation

21. The Fermi level in an N-type semiconductor is closer to:

• a) Valence band
• b) Conduction band
• c) Mid-bandgap
• d) None of the above
  Answer: b) Conduction band

22. When a PN junction diode is forward biased, the current flow is due to:

• a) Majority carriers only
• b) Minority carriers only
• c) Both majority and minority carriers
• d) None of the above
  Answer: c) Both majority and minority carriers

23. Which of the following materials has the highest energy band gap?

• a) Silicon
• b) Germanium
• c) Gallium arsenide
• d) Diamond
  Answer: d) Diamond

24. In reverse bias, the current in a diode is mainly due to:

• a) Majority carriers
• b) Minority carriers
• c) Both majority and minority carriers
• d) None of the above
  Answer: b) Minority carriers

25. What happens to the reverse saturation current if the temperature of a diode increases?

• a) Increases
• b) Decreases
• c) Remains constant
• d) Drops to zero
  Answer: a) Increases

26. The knee voltage of a silicon diode is approximately:

• a) 0.2 V
• b) 0.3 V
• c) 0.7 V
• d) 1.1 V
  Answer: c) 0.7 V

27. What is the primary use of a PN junction diode in electronic circuits?

• a) To amplify signals
• b) To rectify alternating current
• c) To regulate voltage
• d) To generate signals
  Answer: b) To rectify alternating current

28. Which of the following is NOT a property of an intrinsic semiconductor?

• a) High resistivity
• b) Equal electron and hole concentration
• c) Doping is required
• d) Conductivity increases with temperature
  Answer: c) Doping is required

29. The leakage current in a reverse-biased diode is typically:

• a) Very high
• b) Very low
• c) Independent of the reverse voltage
• d) None of the above
  Answer: b) Very low

30. The minority carriers in a P-type semiconductor are:

• a) Electrons
• b) Holes
• c) Neutrons
• d) Protons
  Answer: a) Electrons

31. A diode is said to be in saturation region when:

• a) It is forward biased
• b) It is reverse biased
• c) It is not conducting
• d) It is operating at a high reverse voltage
  Answer: d) It is operating at a high reverse voltage

32. When temperature increases, the intrinsic carrier concentration in a semiconductor:

• a) Increases
• b) Decreases
• c) Remains constant
• d) First increases then decreases
  Answer: a) Increases

33. The cut-in voltage of a germanium diode is approximately:

• a) 0.3 V
• b) 0.7 V
• c) 1.1 V
• d) 2.2 V
  Answer: a) 0.3 V

34. Which of the following is used to describe the level of impurity in a semiconductor?

• a) Conductivity
• b) Doping concentration
• c) Energy band gap
• d) Thermal energy
  Answer: b) Doping concentration

35. In a forward-biased diode, the current is primarily due to the flow of:

• a) Free electrons only
• b) Holes only
• c) Both free electrons and holes
• d) Neutrons
  Answer: c) Both free electrons and holes

36. In a semiconductor, what does the term “drift current” refer to?

• a) Current due to recombination of electrons and holes
• b) Current due to the movement of charge carriers under an electric field
• c) Current due to thermal generation
• d) Current due to external magnetic fields
  Answer: b) Current due to the movement of charge carriers under an electric field

37. Which material has a higher electrical conductivity at room temperature?

• a) Silicon
• b) Germanium
• c) Copper
• d) Diamond
  Answer: c) Copper

38. What happens to the conductivity of an intrinsic semiconductor with an increase in temperature?

• a) Decreases
• b) Increases
• c) Remains constant
• d) Decreases and then increases
  Answer: b) Increases

39. In a PN junction diode, reverse current is due to:

• a) Diffusion of majority carriers
• b) Diffusion of minority carriers
• c) Recombination of carriers
• d) Thermal energy
  Answer: b) Diffusion of minority carriers

40. The term “forward voltage drop” in a diode refers to:

• a) The voltage at which the diode starts conducting in reverse bias
• b) The voltage required to overcome the potential barrier in forward bias
• c) The voltage required to completely stop the current
• d) The voltage drop across the depletion region
  Answer: b) The voltage required to overcome the potential barrier in forward bias

41. Which process is used to introduce impurities into a semiconductor material?

• a) Ionization
• b) Doping
• c) Diffusion
• d) Recombination
  Answer: b) Doping

42. A Zener diode primarily operates in which mode?

• a) Forward bias
• b) Reverse bias
• c) Avalanche breakdown
• d) Cutoff
  Answer: b) Reverse bias

43. What does “breakdown voltage” in a diode refer to?

• a) The maximum reverse voltage a diode can withstand
• b) The voltage at which the diode starts conducting in forward bias
• c) The voltage at which a diode fails
• d) The minimum voltage required for conduction
  Answer: a) The maximum reverse voltage a diode can withstand

44. In an N-type semiconductor, the donor energy level is:

• a) Close to the conduction band
• b) Close to the valence band
• c) At the middle of the band gap
• d) None of the above
  Answer: a) Close to the conduction band

45. Which type of carrier is responsible for conduction in a P-type semiconductor?

• a) Electrons
• b) Holes
• c) Neutrons
• d) Protons
  Answer: b) Holes

46. Which of the following factors increases the width of the depletion region in a PN junction?

• a) Increase in forward bias
• b) Increase in reverse bias
• c) Decrease in reverse bias
• d) Increase in temperature
  Answer: b) Increase in reverse bias

47. The diode current in forward bias condition is:

• a) Directly proportional to the forward voltage
• b) Exponentially related to the forward voltage
• c) Inversely proportional to the forward voltage
• d) Independent of the forward voltage
  Answer: b) Exponentially related to the forward voltage

48. A PN junction diode is used in:

• a) Rectifiers
• b) Oscillators
• c) Amplifiers
• d) Modulators
  Answer: a) Rectifiers

49. What does “reverse recovery time” refer to in a diode?

• a) The time taken to turn off the diode from forward to reverse bias
• b) The time taken to recover from a short circuit
• c) The time taken to switch the diode on
• d) The time taken to build up the depletion region
  Answer: a) The time taken to turn off the diode from forward to reverse bias

50. Which of the following best describes a Schottky diode?

• a) A diode with low forward voltage drop
• b) A diode with a high reverse recovery time
• c) A diode with a low reverse recovery time
• d) A diode with a large depletion region
  Answer: a) A diode with low forward voltage drop

These questions should cover a broad range of concepts related to semiconductor physics and PN junction diodes, suitable for testing understanding of the material in Chapter 1.

Part-2 :Below are next 50 questions for practice

Below are 50 multiple-choice questions covering semiconductor physics, PN junction diodes, Zener diodes, photodiodes, tunnel diodes, LEDs, and half-wave rectifiers. Each question includes four options and the correct answer.

Semiconductor Physics

1. Which of the following is the primary charge carrier in n-type semiconductors?
   • a) Holes
   • b) Electrons
   • c) Protons
   • d) Neutrons
     Answer: b) Electrons
2. The energy gap between the valence band and conduction band in semiconductors is typically in the range of:
   • a) 0.1 to 0.5 eV
   • b) 0.5 to 1.5 eV
   • c) 1.5 to 2.5 eV
   • d) 2.5 to 3.5 eV
     Answer: b) 0.5 to 1.5 eV
3. Which of the following materials is commonly used as a semiconductor?
   • a) Copper
   • b) Silicon
   • c) Gold
   • d) Iron
     Answer: b) Silicon
4. In a semiconductor, the number of charge carriers is mainly controlled by:
   • a) Voltage
   • b) Magnetic field
   • c) Temperature
   • d) Pressure
     Answer: c) Temperature
5. The process of adding impurities to a semiconductor is known as:
   • a) Diffusion
   • b) Ionization
   • c) Doping
   • d) Annealing
     Answer: c) Doping
6. Which type of semiconductor is created by doping with a group III element?
   • a) n-type
   • b) p-type
   • c) Intrinsic
   • d) Extrinsic
     Answer: b) p-type
7. Intrinsic semiconductors have:
   • a) Equal numbers of electrons and holes
   • b) More electrons than holes
   • c) More holes than electrons
   • d) No charge carriers
     Answer: a) Equal numbers of electrons and holes
8. The Fermi level in an intrinsic semiconductor is:
   • a) Near the conduction band
   • b) Near the valence band
   • c) Exactly in the middle of the bandgap
   • d) Outside the bandgap
     Answer: c) Exactly in the middle of the bandgap
9. Which of the following statements is true for a semiconductor at absolute zero temperature?
   • a) It behaves as a perfect conductor.
   • b) It behaves as an insulator.
   • c) It has equal numbers of electrons and holes.
   • d) It has free electrons available for conduction.
     Answer: b) It behaves as an insulator.
10. Which phenomenon explains the flow of charge carriers in a semiconductor?
    • a) Photoelectric effect
    • b) Tunneling
    • c) Diffusion and drift
    • d) Magnetization
      Answer: c) Diffusion and drift

PN Junction Diode

11. A PN junction diode allows current to flow in:
    • a) Both directions
    • b) Only forward direction
    • c) Only reverse direction
    • d) It blocks current in all directions
      Answer: b) Only forward direction
12. The region around the PN junction where no charge carriers are present is called:
    • a) Depletion region
    • b) Conduction band
    • c) Valence band
    • d) Transition region
      Answer: a) Depletion region
13. In forward bias, the width of the depletion region in a PN junction diode:
    • a) Increases
    • b) Decreases
    • c) Remains the same
    • d) Completely disappears
      Answer: b) Decreases
14. The forward voltage drop across a silicon diode is approximately:
    • a) 0.3 V
    • b) 0.7 V
    • c) 1.1 V
    • d) 2.2 V
      Answer: b) 0.7 V
15. When a PN junction diode is reverse-biased, the current through the diode is:
    • a) Very high
    • b) Zero
    • c) Very low
    • d) Equal to the forward current
      Answer: c) Very low
16. The reverse breakdown voltage of a diode is:
    • a) The voltage at which the diode begins to conduct in reverse
    • b) The maximum forward voltage the diode can handle
    • c) The voltage at which the diode is destroyed
    • d) The threshold voltage for forward bias
      Answer: a) The voltage at which the diode begins to conduct in reverse
17. In a diode’s I-V characteristics, the point where the diode starts to conduct significantly in reverse bias is called:
    • a) Knee voltage
    • b) Breakdown voltage
    • c) Forward voltage
    • d) Reverse leakage point
      Answer: b) Breakdown voltage
18. Which of the following is a common application of a PN junction diode?
    • a) Voltage regulation
    • b) Signal rectification
    • c) Power amplification
    • d) Oscillation generation
      Answer: b) Signal rectification
19. A diode used to convert AC to DC is commonly referred to as:
    • a) Rectifier diode
    • b) Zener diode
    • c) LED
    • d) Schottky diode
      Answer: a) Rectifier diode
20. What happens to the reverse saturation current in a PN junction diode if the temperature increases?
    • a) It decreases
    • b) It remains constant
    • c) It increases
    • d) It becomes zero
      Answer: c) It increases

Zener Diode

21. A Zener diode is specifically designed to operate in which region?
    • a) Forward bias region
    • b) Reverse breakdown region
    • c) Active region
    • d) Cut-off region
      Answer: b) Reverse breakdown region
22. The primary application of a Zener diode is:
    • a) Signal modulation
    • b) Voltage regulation
    • c) Power amplification
    • d) Switching
      Answer: b) Voltage regulation
23. The breakdown voltage of a Zener diode is determined by:
    • a) Doping level
    • b) Temperature
    • c) Physical size
    • d) Applied current
      Answer: a) Doping level
24. When used as a voltage regulator, a Zener diode is connected:
    • a) In series with the load
    • b) In parallel with the load
    • c) In series with the power supply
    • d) In parallel with the power supply
      Answer: b) In parallel with the load
25. In a Zener diode, the sharp breakdown occurs because of:
    • a) High reverse current
    • b) Zener effect
    • c) Thermal runaway
    • d) Avalanche effect
      Answer: b) Zener effect
26. What is the typical forward voltage drop of a Zener diode when conducting in the forward direction?
    • a) 0.1 V
    • b) 0.3 V
    • c) 0.7 V
    • d) 1.1 V
      Answer: c) 0.7 V
27. The power dissipation in a Zener diode is given by the product of:
    • a) Zener current and forward voltage
    • b) Zener current and Zener voltage
    • c) Forward current and Zener voltage
    • d) Forward current and forward voltage
      Answer: b) Zener current and Zener voltage
28. A 5.6 V Zener diode is used to regulate the voltage across a load. If the input voltage is 12 V, what is the voltage across the load?
    • a) 5.6 V
    • b) 12 V
    • c) 6.4 V
    • d) 0 V
      Answer: a) 5.6 V
29. A Zener diode is most effective in regulating voltage when the supply voltage:
    • a) Is slightly lower than the Zener voltage
    • b) Is exactly equal to the Zener voltage
    • c) Is higher than the Zener voltage
    • d) Varies randomly
      Answer: c) Is higher than the Zener voltage
30. The current flowing through a Zener diode in reverse bias is primarily due to:
    • a) Majority carriers
    • b) Minority carriers
    • c) Both majority and minority carriers
    • d) No current flows in reverse bias
      Answer: b) Minority carriers

Photo Diode, Tunnel Diode, LED

31. A photodiode operates in which region to detect light?
    • a) Forward bias region
    • b) Reverse bias region
    • c) No bias
    • d) Active region
      Answer: b) Reverse bias region
32. The principle of operation of a photodiode is based on:
    • a) Absorption of photons
    • b) Emission of photons
    • c) Diffusion of electrons
    • d) Tunneling
      Answer: a) Absorption of photons
33. The primary application of a tunnel diode is in:
    • a) Oscillators
    • b) Rectifiers
    • c) Amplifiers
    • d) Voltage regulators
      Answer: a) Oscillators
34. The I-V characteristic curve of a tunnel diode shows:
    • a) Negative resistance region
    • b) Positive resistance region
    • c) Zero resistance region
    • d) Linear resistance region
      Answer: a) Negative resistance region
35. An LED emits light when:
    • a) It is reverse biased
    • b) It is forward biased
    • c) No bias is applied
    • d) It is in saturation mode
      Answer: b) It is forward biased
36. The color of light emitted by an LED depends on:
    • a) The forward voltage
    • b) The material used in the LED
    • c) The applied current
    • d) The size of the LED
      Answer: b) The material used in the LED
37. Which of the following is a key advantage of using LEDs over traditional light sources?
    • a) Lower power consumption
    • b) Higher voltage operation
    • c) Larger size
    • d) Higher operating temperature
      Answer: a) Lower power consumption
38. A tunnel diode is characterized by having:
    • a) A very wide depletion region
    • b) A very narrow depletion region
    • c) High forward voltage drop
    • d) High breakdown voltage
      Answer: b) A very narrow depletion region
39. The efficiency of an LED is measured in terms of:
    • a) Luminous efficacy
    • b) Power dissipation
    • c) Heat generation
    • d) Forward voltage
      Answer: a) Luminous efficacy
40. In a photodiode, as the intensity of incident light increases, the current:
    • a) Decreases
    • b) Remains constant
    • c) Increases
    • d) Becomes zero
      Answer: c) Increases

Half-Wave Rectifiers

41. A half-wave rectifier converts:
    • a) AC to DC
    • b) DC to AC
    • c) AC to AC
    • d) DC to DC
      Answer: a) AC to DC
42. The efficiency of a half-wave rectifier is approximately:
    • a) 25%
    • b) 40.6%
    • c) 50%
    • d) 75%
      Answer: b) 40.6%
43. The output frequency of a half-wave rectifier, given an input frequency of 50 Hz, is:
    • a) 25 Hz
    • b) 50 Hz
    • c) 100 Hz
    • d) 0 Hz
      Answer: b) 50 Hz
44. The ripple factor of a half-wave rectifier is:
    • a) 0.48
    • b) 0.82
    • c) 1.21
    • d) 1.57
      Answer: c) 1.21
45. In a half-wave rectifier, the diode conducts:
    • a) For the entire cycle
    • b) For half of the cycle
    • c) For one-quarter of the cycle
    • d) Only when the input is negative
      Answer: b) For half of the cycle
46. Which of the following components is necessary in a half-wave rectifier circuit?
    • a) Transformer
    • b) Inductor
    • c) Resistor
    • d) Diode
      Answer: d) Diode
47. The peak inverse voltage (PIV) of the diode in a half-wave rectifier must be:
    • a) Equal to the peak input voltage
    • b) Twice the peak input voltage
    • c) Half the peak input voltage
    • d) Irrelevant to the input voltage
      Answer: a) Equal to the peak input voltage
48. A capacitor filter in a half-wave rectifier circuit helps to:
    • a) Increase the ripple
    • b) Decrease the ripple
    • c) Regulate the voltage
    • d) Increase the output frequency
      Answer: b) Decrease the ripple
49. The DC output voltage of a half-wave rectifier is given by:
    • a) V_peak
    • b) V_peak/2
    • c) V_peak x √2
    • d) V_peak/π
      Answer: d) V_peak/π
50. The major disadvantage of a half-wave rectifier is:
    • a) High efficiency
    • b) Low ripple
    • c) Low efficiency
    • d) High cost
      Answer: c) Low efficiency