NEET Physics Class 12 Chapter 6 Solids And Semiconductors Devices Multiple Choice Questions

Chapter 6 Solids And Semiconductors Devices Multiple Choice Questions Exercise -1 Section (A) Semiconductor, Energy Band

Question 1. A N-type semiconductor is

1. Negatively charged
2. Positively charged
3. Neutral
4. None of these

Answer: 3. Neutral

Question 2. The forbidden energy band gap in conductors semiconductors and insulators are EG₁, EG₂, and EG₃ respectively, The relation among them is

1. EG₁ = EG₂ = EG₃
2. EG₁ < EG₂ < EG₃
3. EG₁ > EG₂ > EG₃
4. EG₁ < EG₂ > EG₃

Answer: 2. EG₃₁ < EG₂ < EG₃

Question 3. The mobility of free electrons is greater than that of free holes because

1. They carry a negative charge
2. They are light
3. They mutually collide less
4. They require low energy to continue their motion

Answer: 4. They require low energy to continue their motion

Question 4. Electric conduction in a semiconductor takes place due to

1. Electrons Only
2. Holes Only
3. Both Electrons And Holes
4. Neither electrons nor Holes

Answer: 3. Both Electrons And Holes

Question 5. Let n p and n e be the numbers of holes and conduction electrons in an intrinsic semiconductor

1. n_p > n_e
2. n_p = n_e
3. n_p < n_e
4. n_p ≠ n_e

Answer: 2. n_p = n_e

Question 6. Let np and ne be the numbers of holes and conduction electrons in an extrinsic semiconductor

1. n_p > n_e
2. n_p = n_e
3. n_p < n_e
4. n_p ≠ n_e

Answer: 4. n_p ≠ n_e

Question 7. An electric field is applied to a semiconductor. Let the number of charge carriers be n and the average drift speed be. If the temperature is increased,

1. Both N And υ Will Increase
2. N Will Increase But υ Will Decrease
3. υ Will Increases But N Will Decrease
4. Both N And υ Will Decrease

Answer: 2. N Will Increase But υ Will Decrease

Question 8. When an impurity is doped into an intrinsic semiconductor, the conductivity of the semiconductor

1. Increases
2. Decreases
3. Remains The Same
4. Become Zero

Answer: 1. Increases

Question 9. In a P-type semiconductor, the acceptor level is 57 meV, above the valence band. The maximum wavelength of light required to produce a hole will be

1. 57 A°
2. 57 × 10¯³ A°
3. 217100 A°
4. 11.61 × 10 A°

Answer: 3. 217100 A°

Question 10. The electrical conductivity of pure germanium can be increased by

1. Increasing The Temperature
2. Doping Acceptor Impurities
3. Doping Donor Impurities
4. Irradiating Ultraviolet Light On It.

Answer: 1. Increassing The Temperature

Question 11. A semiconductor is doped with a donor impurity

1. The hole concentration increases
2. The hole concentration decreases
3. The electron concentration increases
4. The electron concentration decreases

Answer: 2. The hole concentration decreases

Question 12. Which of the following when added as an impurity into silicon produces an n-type semiconductor?

1. P
2. Al
3. B
4. Mg

Answer: 1. P

Question 13. Which of the following diagrams correctly represents the energy levels in the p-type semiconductor?

Question 14. In p-type semiconductor, the major charge carriers are :

1. Holes
2. Electrons
3. Protons
4. Neutrons

Answer: 3. Protons

Question 15. Copper and silicon are cooled from 300 K to 60K, and the specific resistance:-

1. Decrease in copper but an increase in silicon
2. Increase in copper but an increase in silicon
3. Increase in both
4. Decrease in both

Answer: 1. Decrease in copper but increase in silicon

Question 16. The value of the forbidden energy gap for the conductor is:

1. 1 eV
2. 6 eV
3. 0 eV
4. 3 eV

Answer: 1. 1 eV

Question 17. Ga As is a /an :

1. Element Semiconductor
2. Alloy Semiconductor
3. Bad Conductor
4. Metalic Semiconductor

Answer: Alloy Semiconductor

Question 18. The number of free electrons in Si at normal temperature is :

1. 2.5 × 106 per cm3
2. 1.5 × 1010 per cm3
3. 1.5 × 1013 per cm3
4. 2.5 × 1013 per cm3

Answer: 2. 1.5 × 1010 per cm3

Question 19. Hole are the charge carriers in :

1. Semiconductor
2. Ionic Solids
3. P-Type Semiconductor
4. Metals

Answer: 1. Semiconductor

Question 20. Regarding a semi-conductor which one of the following is wrong?

1. There are no free electrons at 0 K
2. There are no free electrons at room temperature
3. The number of free electrons increases with the rise in temperature
4. The charge carriers are electrons and holes.

Answer: 2. There are no free electrons at room temperature

Question 21. At absolute zero, Si acts as :

1. Non-Metal
2. Metal
3. Insulator
4. None Of These

Answer: 3. Insulator

Question 22. By increasing the temperature, the specific resistance of a conductor and ~ semiconductor:

1. Increases For Both
2. Decreases For Both
3. Increases, Decreases Respectively
4. Decreases, Increases Respectively

Answer: 3. Increases, Decreases Respectively

Question 23. The energy band gap is maximum in:

1. Metals
2. Superconductors
3. Insulators
4. Semiconductors

Answer: 3. Insulators

Question 24. A strip of copper and another of germanium are cooled from room temperature to 80 K. The resistance of :

1. Each Of These Decreases
2. Copper Strip Increases And That Of Germanium Decreases
3. Copper Strip Decreases And That Of Germanium Increases
4. Each Of These Increases

Answer: 3. Copper Strip Decreases And That Of Germanium Increases

Question 25. The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the:

1. Crystal Structure
2. Variation Of The Number Of Charges Carries With Temperature
3. Type Of Bonding
4. Variation Of Scattering Mechanism With Temperature

Answer: 2. Variation Of The Number Of Charges Carries With Temperature

Question 26. In p-type semiconductors germanium is doped with :

1. Gallium
2. Aluminium
3. Boron
4. All Of These

Answer: 4. All Of These

Question 27. In a good conductor of electricity, the type of bonding that exists is :

1. Ionic
2. Van Der Waal
3. Covalent
4. Metallic

Answer: 4. Metallic

Question 28. Which of the following statements is true for an n-type semiconductor?

1. The donor level lies closely below the bottom of the conduction band
2. The donor level lies closely above the top of the valence band
3. The donor level lies at the halfway mark of the forbidden energy gap
4. None of the above

Answer: 1. The donor level lies closely below the bottom of the conduction band

Question 29. An n-type semiconductor is

1. Negatively Charged
2. Positively Charged
3. Neutral
4. None Of The Above

Answer: 3. Neutral

Question 30. The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the

1. Crystal Structure
2. Change In The Number Of Charge Career
3. Type Of Bonding
4. None Of These

Answer: 2. Change In The Number Of Charge Career

Question 31. In P-Type Semiconductors Majority Charge Carriers Are

1. Electrons
2. Holes
3. Neutrons
4. Protons

Answer: 2. Holes

Question 32. Wire P and Q have the same resistance at ordinary (room) temperature. When heated, the resistance of P increases, and that of Q decreases. we conclude that

1. p and Q are conductors of different materials.
2. p is an n-type semiconductor and Q is a p-type semiconductor
3. p is semiconductor and Q is conductor
4. p is conductor and Q is semiconductor

Answer: 4. p is a conductor and Q is a semiconductor

Question 33. The resistance of a semiconductor and a conductor:

1. Increases With Temperature For Both
2. Decreases With Temperature For Both
3. Increases And Decreases Respectively With Increase In Temperature
4. Decreases And Increases Respectively With Increase In Temperature

Answer: 4. Decreases And Increases Respectively With Increase In Temperature

Question 34. In semiconductors at room temperature

1. The valence band is filled and the conduction band is partially filled
2. The valence band is filled
3. The conduction band is empty
4. The valence band is partially empty and the conduction band is partially filled

Answer: 4. The valence band is partially empty and the conduction band is partially filled

Question 35. Carbon, Silicon, and Germanium atoms have four valence electrons each. Their valence and conduction bonds are separated by energy band gaps represented by (Eg ) C, (Eg)si, and (Eg) Ge respectively. Which one of the following relationships is true in their case

1. (E_g)_c < (E_g)_Ge
2. (E_g)_c > (E_g)_si
3. (E_g)_c = (E_g)_si
4. (E_g)_c < (E_g)_si

Answer: 2. (E_g)_c > (Eg)_si

Question 36. In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is a/an :

1. P-Type Semiconductor
2. Insulator
3. Metal
4. N-Type Semiconductor

Answer: 1. P-Type Semiconductor

Question 35. Choose the correct option for the forward-biased characteristics of a p–n junction.

Answer: 3.

Question 36. The emitter-base junction of a transistor is …….biased while the collector-base junction is …….biased

1. Reverse, forward
2. Reverse, reverse
3. Forward, forward
4. Forward, reverse

Answer: 4. Forward, reverse

Question 37. If the two ends of a P-N junction are joined by a wire-

1. There will not be a steady current in the circuit
2. There will be a steady current from the N-side to the P-side
3. There will be a steady current from the P-side to the N-side
4. There may or may not be a current depending upon the resistance of the connecting wire.

Answer: 1. There will not be a steady current in the circuit

Question 38. The region that has no free electrons and holes in a P-N juction is-

1. P-region
2. N-region
3. Junction
4. Depletion Region

Answer: 4. Depletion Region

Question 39. In the P-N junction at the near junction, there are-

1. Only Positive Ions
2. Only Negative Ions
3. Positive And Negative Ion Both
4. Electron And Holes Both

Answer: 3. Positive And Negative Ion Both

Question 40. A diode is made forward biased by a two-volt battery however there is a drop of 0.5 V across the diode which is independent of the current. Also, a current greater than 10 mA produces large joule loss and damages the diode. If the diode is to be operated at 5 mA, the series resistance to be put is-

1. 3 KΩ
2. 300 KΩ
3. 300Ω
4. 200 KΩ

Answer: 3. 300Ω

Question 41. The ratio of resistance for forward to reverse bias of the P–N junction diode is-

1. 10²: 1
2. 10–²: 1
3. 1: 10–4
4. 1: 10

Answer: 4. 1: 10

Question 42. Zener diode is used-

1. As an amplifier
2. As a rectifier
3. As an oscillator
4. As a voltage regulator

Answer: 2. As a rectifier

Question 43. The zener breakdown will occur if-

1. The impurity level is low
2. The impurity level is high
3. Impurity is less on the N-side
4. Impurity is less on P-side

Answer: 2. Impurity level is high

Question 44. In the given fig. which of the diodes are forward-biased

1. 1,2,3
2. 2,4,5
3. 1,3,4
4. 2,3,4

Answer: 1. 1,2,3

Question 45. Consider the following statements A and B and identify the correct answer-

• A zener diode is always connected in reverse bias.
• The potential barrier of a P-N junction lies between 0.1 to 0.3 V approximately.

Choose The Correct Answer

1. A and B are correct
2. A and B are wrong
3. A is correct, but B is wrong
4. A is wrong, but B is correct

Answer: 3. A is correct, but B is wrong

Question 46. The function of the rectifier is

1. To convert AC into DC
2. To convert dc into ac
3. Both and
4. None of these

Answer: 1. To convert AC into dc

Question 47. The cause of the potential barrier in a p-n diode is:

1. Depletion Of Positive Charges Near The Junction
2. Concentration Of Positive Charges Near The Junction
3. Depletion Of Negative Charges Near The Junction
4. Concentration Of Positive And Negative Charges Near The Junction

Answer: 4. Concentration Of Positive And Negative Charges Near The Junction

Question 48. A semi-conducting device is connected in a series in a circuit with a battery and a resistance. A current is allowed to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be:

1. A P-N Junction
2. An Intrinsic Semiconductor
3. A P-Type Semiconductor
4. An N-Type Semiconductor

Answer: 1. A P-N Junction

Question 49. In a junction diode, the holes are due to:

1. Protons
2. Extra Electrons
3. Neutrons
4. Missing Electrons

Answer: 4. Missing Electrons

Question 50. The depletion layer consists of:

1. Electrons
2. Protons
3. Mobile Charge Carriers
4. Immobile Ions

Answer: 4. Immobile Ions

Question 51. In forward bias the width of the depletion layer in a p-n junction diode:

1. Increases
2. Decreases
3. Remains Constant
4. First Increases Then Decreases

Answer: 2. Decreases

Question 52. The current (I) in the circuit will be

1. \(\frac{5}{40} \mathrm{~A}\)
2. \(\frac{5}{50} \mathrm{~A}\)
3. \(\frac{5}{10} \mathrm{~A}\)
4. \(\frac{5}{20} \mathrm{~A}\)

Answer: 2. \(\frac{5}{50} \mathrm{~A}\)

Question 53. In a P-N junction diode not connected to any circuit-

1. High potential at the N side and low potential at the P side
2. High potential at the P side and low potential at the N side
3. P and N both have at same potential
4. The potentials of the N side and P side are undetermined

Answer: 1. High potential at the N side and low potential at the P side

Question 54. In a PN junction:-

1. High potential at the N side and low potential at the P side
2. High potential at the N side and low potential at the N side
3. P and N both have at same potential
4. Undetermined

Answer: 1. High potential at the N side and low potential at the P side

Question 55. Reverse bias applied to a junction diode-

1. Lowers the potential barrier
2. Raises the potential barrier
3. Increases the majority carrier’s current
4. Decreases the minority carrier’s current

Answer: 2. Raises the potential barrier

Question 56. The barrier potential of a p-n junction diode does not depend on-

1. Diode design
2. Temperature
3. Forward bias
4. Doping density

Answer: 1. Diode design

Question 57. The inverse saturation current in a P-N junction diode at 27°C is 10–5 amp. The value of forward current at 0.2 volts will be (e7.62 = 2038.6)

1. 2037.6 × 10–3 A
2. 203.76 × 10–3 A
3. 20.376 × 10–3 A
4. 2.0376 × 10–3 A

Answer: 3. 20.376 × 10–3 A

Question 58. The reason for the potential barrier in the p-n junction is:

1. Excess Of Positive Charge At Junction
2. Deficiency Of Positive Charge At Junction
3. Deficiency Of Negative Charge At Junction
4. Excess Of Positive And Negative Charge At Junction

Answer: 4. Excess Of Positive And Negative Charge At Junction

Question 59. In p-n junction depletion region decreases when:

1. Zero Bias
2. Forward Bias
3. Reverse Bias
4. Temperature Decreases

Answer: 2. Forward Bias

Question 60. Two identical P-N junctions may be connected in series with a battery in three ways (fig below). The potential drops across the two P-N junctions are equal in

1. Circuits 1 and 2
2. Circuits 2 and 3
3. Circuit 3 and 1
4. Circuit 1 only

Answer: 3. Circuit 3 and 1

Question 62. In a P-N junction diode which is not connected to any circuit-

1. The potential is the same everywhere
2. The P-type side is at a higher potential than the N-type side
3. There is an electric field at the junction directed from the N-type side to the P-type side
4. There is an electric field at the junction directed from the P-type side to the N-type side

Answer: 2. The P-type side is at a higher potential than the N-type side

Question 63. For the given circuit shown in Fig, to act as a full wave rectifier, a.c. input should be connected across ……..and……..the d.c. output would appear across……..and……..

1. A, C and B, D
2. B, D and A, C
3. A, B C, D
4. C, A and D, B

Answer: 3. A, B C, D

Question 64. In a……biased P-N junction the net flow holes is from the N-region to the P-region-

1. Forward Bias
2. Reverse Bias
3. no
4. Both 1 and 2

Answer: 2. Reverse Bias

Question 65. For making the p-n junction diode forward biased:

1. The same Potential Is Applied
2. Greater Potential Is Given To N Compared To P
3. Greater Potential Is Given To P Compared To N
4. Unbalanced Concentration

Answer: 3. Greater Potential Is Given To P Compared To N

Question 66. When a p-n junction diode is reverse-biased, then

1. No Current Flows
2. The Depletion Region Is Increased
3. The Depletion Region Is Reduced
4. The Height Of The Potential Barrier Is Reduced

Answer: 2. The Depletion Region Is Increased

Question 67. In the middle of the depletion layer of reverse biased p – n juction, the

1. Electric Field Is Zero
2. Potential Is Maximum
3. The Electric Field Is the Maximum
4. Potential Is Zero

Answer: Electric Field Is Zero

Question 68. If the input is given between A and C, then the output at the ends of R will be

1. Fully Rectified
2. Half Rectified
3. Ac
4. None Of These

Answer: 2. Half Rectified

Question 69. Of the diodes shown in the following diagrams, which one of the diodes is reverse biased?

Answer: 2.

Question 70. Application of a forward bias to a p-n junction –

1. Widens the depletion zone
2. Increases the number of donors on the N-side
3. Increases the potential difference across the depletion zone
4. Increases the electric field in the depletion zone

Answer: 4. Increases the electric field in the depletion zone

Question 71. A forward-biased diode is:-

Answer: 4.

Question 72. A p-n photodiode is made of a material with a band gap of 2.0 eV. The minimum frequency of the radiation that can be absorbed by the material is nearly

1. 10 × 1014 Hz
2. 5 × 1014 Hz
3. 1 × 1014 Hz
4. 20 × 1014 Hz

Answer: 2. 5 × 1014 Hz

Question 73. When the P-N junction diode is forward-biased, then-

1. The Depletion Region Is Reduced And Barrier Height Is Increased.
2. The Depletion Region Is Widened And the Barrier Height Is Reduced.
3. Both The Depletion Region And Barrier Height Are Reduced.
4. Both The Depletion Region And Barrier Height Are Increased.

Answer: 3. Both The Depletion Region And Barrier Height Are Reduced.

Question 74. In a full wave rectifier circuit operating from 50 Hz mains frequency, the fundamental frequency in the ripple would be:

1. 50Hz
2. 25Hz
3. 100Hz
4. 70.7Hz

Answer: 3. 100Hz

Question 75. In the following, which one of the diodes is reverse-biased?

Answer: 2.

Question 76. The circuit has two oppositely connected ideal diodes in parallel. What is the current flowing in the circuit?

1. 2.31A
2. 1.33A
3. 1.71A
4. 2.00A

Answer: 4. 2.00A

Question 77. The drift current in a p-n junction is

1. From The N-Side To The P-Side
2. From The P-Side To The N-Side
3. From The N-Side To The P-Side If The Junction Is Forward-Baised And In The Opposite Direction If It Is Reverse-Biased
4. From The P-Side To The N-Side If The Junction Is Forward-Biased And In The Opposite Direction If It Is Reverse-Baised

Answer: 1. From The N-Side To The P-Side

Question 78. The diffusion current in a p-n junction is

1. From The N-Side To The P-Side
2. From The P-Side To The N-Side
3. From The N-Side To The P-Side Of The Junction Is Forward-Biased And In The opposite direction If It Is Reverse-Baised
4. From The P-Side To The N-Side If The Junction Is Forward-Baised And In The Opposite Direction If It Is Reverse-Biased

Answer: 2. From The P-Side To The N-Side

Question 79. A semiconducting device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be

1. An Intrinsic Semiconductor
2. A P-Type Semiconductor
3. An N-Type Semiconductor
4. A P-N Junction

Answer: 4. A P-N Junction

Question 80. If the two ends P and N of a P-N of a P-N diode junction are joined by a wire

1. There will not be a steady current in the circuit
2. There will be a steady current from the N side to the P side
3. There will be a steady current from the P side to the N side
4. There may not be a current depending upon the resistance of the connecting wire

Answer: 1. There will not be a steady current in the circuit

Question 81. To make a PN junction conducting

1. The value of forward bias should be more than the barrier potential
2. The value of forward bias should be less than the barrier potential
3. The value of reverse bias should be more than the barrier potential
4. The value of reverse bias should be less than the barrier potential

Answer: 1. The value of forward bias should be more than the barrier potential

Question 82. Zener diode is used as

1. Half Wave Rectifier
2. Full Wave Rectifier
3. Ac Voltage Stabilizer
4. Dc Voltage Stabilizer

Answer: 3. Ac Voltage Stabilizer

Question 83. In the P-N junction, the barrier potential offers resistance to

1. Free electrons in the N region and holes in the P region
2. Free electrons in the P region and holes in the N region
3. Only free electrons in the N region
4. Only holes in the P region

Answer: 1. Free electrons in the N region and holes in the P region

Question 84. Two identical P-N diodes are connected in series in the following ways. Maximum current will flow in a circuit

1. A
2. B
3. C
4. D

Answer: 2. B

Question 85. In the following circuit readings in ammeters A1 and A2 will be

1. 0.2A, Zero
2. Xero, o.2 A
3. 0.2A, 0.2A
4. 0.2A,0.4A

Answer: 2. Xero, o.2 A

Question 86. A light-emitting diode has a voltage drop of 2 v across it and passes a current of 10 A. When it operates with a 6 v battery through a limiting resistor R, the value of R is

1. 40 kΩ
2. 4 kΩ
3. 200 kΩ
4. 400 kΩ

Answer: 4. 400 kΩ

Chapter 6 Solids And Semiconductors Devices Multiple Choice Questions Section (C): Transistors

Question 1. An amplifier is nothing but an oscillator with –

1. Positive Feedback
2. High Gain
3. No Feed Back
4. Negative Feed Back

Answer: 1. Positive Feedback

Question 2. In A Normal Operation Of A Transistor,

1. The Base-Emitter Junction Is Forward-Biased
2. The Base-Collector Junction Is Forward-Biased
3. The Base-Emitter Junction Is Reverse-Baised
4. The Base-Collector Junction Is Reverse-Baised

Answer: 1. The Base-Emitter Junction Is Forward-Biased

Question 3. In the case of constants α and β of a transistor

1. α = β
2. β < 1 α > 1
3. αβ = 1
4. β > 1 α< 1

Answer: 4. β > 1 α< 1

Question 4. If α= 0.98 and current through emitter i e = 20 mA, the value of β is

1. 4.9
2. 49
3. 96
4. 9.6

Answer: 2. 49

Question 5. The transfer ratio B of a transistor is 50. the input resistance of the transistor when used in the common emitter configuration is 1 kΩ The peak value of the collector AC for an AC input voltage of 0.01 V peak is:

1. 100 µA
2. 0.01 mA
3. 0.25 mA
4. 500 µA

Answer: 4. 500 µA

Question 6. For a common emitter circuit if E I = 0.98 then the current gain for the common emitter circuit will be :

1. 49
2. 98
3. 4.9
4. 25.5

Answer: 1. 49

Question 7. A n-p-n transistor conducts when

1. Both Collector And Emitter Are Positive Concerning The Base
2. Collector Is Positive And Emitter Is Negative Concerning The Base
3. Collector Is Positive And Emitter Is At the Same Potential As The Base
4. Both Collector And Emitter Are Negative Concerning The Base

Answer: 2. Collector Is Positive And Emitter Is Negative Concerning The Base

Question 8. A Transistor (Pnp Or Npn) Can Be Used As

1. An Amplifier
2. An Oscillator
3. A Switch
4. All Of These

Answer: 4. All Of These

Question 9. The part of a transistor that is most heavily doped to produce a large number of majority charge carries is :

1. Emitter
2. Base
3. Collector
4. Can Be Any Of The Above Three

Answer: 1. Emitter

Question 10. In a common-base configuration of transistor. α = 0.98, I B = 0.02 mA, RL = 5 kΩ. The output voltage across the load is:

1. 3.2 v
2. 4.9v
3. 5.2v
4. 6.2v

Answer: 2. 4.9v

Question 11. The minimum potential difference between the base and emitter required to switch a silicon transistor ‘ON’ is approximately?

1. 1 V
2. 3 V
3. 5 V
4. 4.2 V

Answer: 1. 1 V

Question 12. In the circuit shown in the figure, the current gainβ= 100 for an npn transistor. The bias resistance RB so that V CE = 5V is (VBE << 10 V)

1. 2 × 103Ω
2. 105Ω
3. 2 × 105Ω 
4. 5 × 105Ω

Answer: 3. 2 × 105Ω

Question 13. In a common emitter amplifier using an output resistance of 5000 ohms and input resistance of 2000 ohm, if the peak value of input signal voltage is 10 mV and β= 50 then the calculated power gain will be

1. 6.25 × 103
2. 1.4
3. 62.5
4. 2.5 × 10

Answer: 1. 6.25 × 103

Question 14. A transistor oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produces oscillations of frequency. If L is doubled and C is changed to 4C, the frequency will be:

1. \(\frac{f}{4}\)
2. 8f
3. \(\frac{f}{2 \sqrt{2}}\)
4. \(\frac{f}{2}\)

Answer: 3. \(\frac{f}{2 \sqrt{2}}\)

Question 15. A transistor is operated in a common emitter configuration at constant collector voltage Vc = 1.5 V such that a change in the base current from 100 µA to 150 µA produces a change in the collector current from 5 mA to 10 mA. The current gain (β) is:-

1. 67
2. 75
3. 100
4. 50

Answer: 3. 100

Question 16. A common emitter amplifier has a voltage gain of 50 and a current gain is 25. The power gain of the amplifier is:

1. 500
2. 1000
3. 1250
4. 100

Answer: 3. 1250

Question 17. When npn transistor is used as an amplifier:

1. Electrons Move From Base To Collector
2. Holes Move From Emitter To Base
3. Electrons Move From Collector To Base
4. Holes Move From Base To Emitter

Answer: 4. Holes Move From Base To Emitter

Question 18. In a common base amplifier, the phase difference between the input signal voltage and output voltage is :

1. \(\frac{\pi}{4}\)
2. Zero
3. \(\frac{\pi}{2}\)

Answer: 3. Zero

Question 19. In a common–base mode of transistor, the collector current is 5.488 mA for an emitter current of 5.60 mA. The value of the base current amplification factor will be:

1. 49
2. 50
3. 51
4. 48

Answer: 1. 49

Question 20. A working transistor with its three legs marked P, Q, and R is tested using a multimeter. No conduction is found between P and Q. By connecting the common (negative) terminal of the multimeter to R and the other (positive) terminal to P or Q, some resistance is seen on the multimeter. Which of the following is true for the transistor?

1. It is a PNP transistor with R as a collector
2. It is a PNP transistor with R as an emitter
3. It is an NPN transistor with R as a collector
4. It is an NPN transistor with R as the base

Answer: 4. It is a PNP transistor with R as a collector

Question 21. An N-P-N transistor is connected in a common emitter configuration in which the collector supply is 9V and the voltage drop across the load resistance of 1000 connected in the collector circuit is 1 V. If the current amplification factor is (25/26), if the internal resistance of the transistor is 200, then which of the following options is incorrect amplification factor is (25/26), if the internal resistance of the transistor is 200, then which of the following options is incorrect

1. \(V_{C E}=8 \mathrm{~V}\)
2. The collector current is 1.0 mA
3. Voltage gain \(\frac{50}{23}\) and power gain is 4.6
4. The emitter current is 2.04 mA

Answer: 3. Voltage gain \(\frac{50}{23}\) and power gain is 4.6

Question 22. In a common emitter (CE) amplifier having a voltage gain of G, the transistor used has a transconductance of 0.03 mho and a current gain of 25. If the above transistor is replaced with another one with a transconductance of 0.02 mho and a current gain of 20, the voltage gain will be:

1. 1.5 g
2. \(\frac{1}{3} G\)
3. \(\frac{5}{4} G\)
4. \(\frac{2}{3} G\)

Answer: 4. \(\frac{2}{3} G\)

Question 23. The input resistance of a silicon transistor is 100. Base current is changed by 40 A which results in a change in collector current by 2mA. This transistor is used as a common emitter amplifier with a load resistance of 4 K. The voltage gain of the amplifier is :

1. 2000
2. 3000
3. 4000
4. 1000

Answer: 1. 2000

Question 24. For a given CE biasing circuit, if the voltage across the collector-emitter is 12V and current gain is 100, and the base current is 0.04 mA then determine the value collector resistance RC.

1. 1200
2. 200
3. 400
4. 2000

Answer: 4. 2000

Question 25. The A-C current gain of a transistor is β= 19. In its common-emitter configuration, What will be the change in the emitter current for a change of 0.4 mA in the base current?

1. 7.6 mA
2. 7.2 mA
3. 8 mA
4. 6.8 mA

Answer: 3. 8 mA

Chapter 6 Solids And Semiconductors Devices Multiple Choice Questions Section D: Logic Gates

Question 1. The truth table shown in the figure is for

1. A 0 0 1 1
2. B 0 1 0 1
3. Y 1 0 0 1
4. XOR
5. AND
6. XNOR
7. OR

Answer: 1. XOR

Question 2. For the given combination of gates, if the logic states of inputs A, B, C are as follows A = B = C = 0 and A = B = 1, C = 0 then the logic states of output D are

1. 0,0
2. 0,1
3. 1,0
4. 1,1

Answer: 4. 1,1

Question 3. A gate has the following truth table

1. P 1 1 0 0
2. Q 1 0 1 0
3. R 1 0 0 0

The gate is

1. NOR
2. OR
3. NAND
4. AND

Answer: 4. AND

Question 4. Which of the following gates will have an output of 1

Answer: 3.

Question 5. If A and B are two inputs in the AND gate, then the AND gate has an output of 1 when the values of A and B are

1. A = 0, B = 0
2. A = 1, B = 1
3. A = 1, B = 0
4. A = 0, B = 1

Answer: 4. A = 0, B = 1

Question 6. The Boolean equation of the NOR gate is

1. C=A+B
2. \(\mathrm{C}=\overline{\mathrm{A}+\mathrm{B}}\)
3. C=A.B
4. \(\mathrm{C}=\overline{\mathrm{A} \cdot \mathrm{B}}\)

Answer: 1. C=A+B

Question 7. The following circuit represents

1. OR gate
2. XOr Gate
3. AND gate
4. NAND gate

Answer: 2. XOr Gate

Question 8. The following truth table represents which logic gate

1. XOR
2. NOT
3. NAND
4. AND

Answer: 4. AND

Question 9. The given truth table is for which logic gate:-

1. NAND
2. XOR
3. NOR
4. OR

Answer: 1. NAND

Question 10. The truth table is of the

1. NAND gate
2. OR gate
3. NOT gate
4. And gate

Answer: 1. NAND gate

Question 11. Zener dode is used for :-

1. Rectification
2. Stabilization
3. Amplification
4. Producing oscillations in an oscillator

Answer: 2. Stabilisation

Question 12. The output of the OR gate is 1:

1. If either or both inputs are 1
2. Only if both inputs are 1
3. If either input is zero
4. If both inputs are zero

Answer: 1. If either or both inputs are 1

Question 13. Name the type of gate used in the circuit given, find the relation between A, B, and Y, and draw the truth table.

1. AND gate
2. NAND gate
3. NOR gate
4. OR gate

Answer: 1. AND gate

Question 14. The following figure shows a logic gate circuit with two inputs A and B and the output C. The voltage waveforms of A, B, and C are as shown below –

The logic circuit gate is:-

1. AND gate
2. NAND gate
3. NOR gate
4. OR gate

Answer: 1. AND gate

Question 15. The circuit is equivalent to

1. AND gate
2. NAND gate
3. NOR gate
4. OR gate

Answer: 3. NOR gate

Question 16. In the circuit below, A and B represent two inputs and C represents the output.

1. The circuit represents
2. AND gate
3. NAND gate
4. OR gate
5. NOR gate

Answer: 3. OR gate

Question 17. Given below are symbols for some logic gates

The XOR gate and NOR gate respectively are

1. 1 and 2
2. 2 and 3
3. 3 and 4
4. 1 and 4

Answer: 2. 2 and 3

Question 18. The following truth table corresponds to the logic gate

1. A 0 0 1 1
2. B 0 1 0 1
3. X 0 1 1 1
4. NAND
5. OR
6. AND
7. XOR

Answer: 2. OR

Question 19. A truth table is given below. Which of the following has this type of truth table

1. A 0 1 0 1
2. B 0 0 1 1
3. y 1 0 0 0
4. XOR gate
5. NOR gate
6. AND gate
7. OR gate

Answer: 2. AND gate

Question 20. An AND gate can be prepared by repetitive use of

1. NOT gate
2. OR gate
3. NAND gate
4. NOR gate

Answer: 4. NOR gate

Chapter 6 Solids And Semiconductors Devices Multiple Choice Questions Exercise 2

Question 1. For a given circuit potential difference VAB is-

1. 10V
2. 20V
3. 30V
4. None

Answer: 1. 10V

Question 2. The resistance of a discharge tube is:

1. Zero
2. Ohmic
3. Non-ohmic
4. Infinity

Answer: 3. Non-ohmic

Question 3. For a transistor \(\frac{I_c}{I_E}=0.96\) then current gain for common emitter configuration:

1. 12
2. 6
3. 48
4. 24

Answer: 4. 24

Question 4. For the given circuit of the P-N junction diode, which is correct

1. In F.B. the voltage across R is V
2. In R.B. the voltage across R is V
3. In F.B. the voltage across R is 2 V
4. In R.B. the voltage across R is 2 V

Answer: 1. In F.B. the voltage across R is V

Question 5. A sinusoidal voltage of peak-to-peak value of 310 V is connected in series with a diode and a load resistance R so that Half-wave rectification occurs. If the diode has negligible forward resistance, the root mean square voltage across the load resistance is

1. 310 V
2. 155 V
3. 109.5 V
4. 77.5

Answer: 4. 77.5

Question 6. A photocell employs the photoelectric effect to convert

1. Change in the frequency of light into a change in electric voltage
2. Change in the intensity of illumination into a change in photoelectric current
3. Change in the intensity of illumination into a change in the work function of the photocathode
4. Change in the frequency of light into a change in the electric current

Answer: 2. Change in the intensity of illumination into a change in photoelectric current

Question 7. Semiconductor Ge has a forbidden gap of 1.43 eV. Calculate the maximum wavelength that results from the electron-hole combination.

1. 8654 Å
2. 7650 Å
3. 4982 Å
4. 10500 Å

Answer: 1. 8654 Å

Question 8. 1. For a given transistor circuit, the base current is 10 A and the collector current is 5.2 mA. Can this transistor circuit be used as an amplifier? Your answer must be supported with a proper explanation.

Answer: yes, \(\beta=520\)

2. For a common emitter amplifier, the current gain is 69. If the emitter current is 7 mA then calculate the base current and collector current.

Answer: \(i_b=0.1 \mathrm{~mA}, \mathrm{i}_{\mathrm{c}}=6.9 \mathrm{Ma}\)

Chapter 6 Solids And Semiconductors Devices Multiple Choice Questions Exercise 3 Part – 1: Neet Or Aipmt Question (Previous Years)

Question 1. A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. It can detect a signal of wavelength

1. 6000 Å
2. 4000 nm
3. 6000 nm
4. 4000 Å

Answer: 4. 4000 Å

Question 2. The symbolic representation of four logic gates

The logic symbols for OR, NOT, and NAND gates are respectively

1. (1) (3), (4), (2)
2. (2) (4), (1), (3)
3. (3) (4), (2), (1)
4. (4) (1), (3), (4)

Answer: 3. (3) (4), (2), (1)

Question 3.

1. Draw the circuit diagram of the reversed bias p-n junction.
2. Draw the output waveform across the diode in the given circuit.

3. Draw the truth table for the given logic gate.

Question 4. Which one of the following statements is false?

1. Pure Si doped with trivalent impurities gives a p-type semiconductor.
2. The majority of carriers in a n-type semiconductor are holes.
3. Minority carriers in a p-type semiconductor are electrons.
4. The resistance of intrinsic semiconductors decreases with an increase in temperature.

Answer: 2. Majority of carriers in a n-type semiconductor are holes.

Question 5. The device that acts as a complete electronic circuit is

1. Junction diode
2. Integrated circuit
3. Junction transistor
4. Zener diode

Answer: 2. Integrated circuit

Question 6. A common emitter amplifier has a voltage gain of 50, an input impedance of 100, and an output impedance of 200. The power gain of the amplifier is

1. 500
2. 1000
3. 1250
4. 50

Answer: 3. 1250

Question 7. To get an output Y = 1 from the circuit shown below the input must be

1. 0 1 0
2. 0 0 1
3. 1 0 1
4. 1 0 0

Answer: 3. 1 0 1

Question 8. The following figure shows a logic gate circuit with two inputs A and B and the output Y. The voltage waveforms of A, B, and Y are as given.

The logic gate is

1. NOR gate
2. OR gate
3. AND gate
4. NAND gate

Answer: 4. NAND gate

Question 9. In the following figure, the diodes which are forward-biased, are:

1. (3) only
2. (3) and (1)
3. (2) and (4)
4. (1), (2), and (4)

Answer: 2. (3) and (1)

Question 10. Pure Si at 500K has an equal number of electron (n e) and hole (NH) concentrations of 1.5 × 1016 m–3. Doping by indium increases n h to 4.5 x 1022 m–3. The doped semiconductor is of:

1. n-type with electron concentration n e = 5 × 1022 m–3
2. p-type with electron concentration n e = 2.5 ×1010 m–3
3. n-type with electron concentration n e = 2.5 × 1023 m–3
4. p-type having electron concentrations n e = 5 × 109 m–3

Answer: 4. p-type having electron concentrations n e = 5 × 109 m–3

Question 11. A Zener diode, having a breakdown voltage equal to 15V, is used in a voltage regulator circuit shown in the figure. The current through the diode is:

1. 10 mA
2. 15 mA
3. 20 mA
4. 5 mA

Answer: 4. 5 mA

Question 12. A transistor is operated in a common emitter configuration at VC = 2V such that a change in the base current from 100 μA to 300 μA produces a change in the collector current from 10 mA to 20 mA. The current gain is:

1. 50
2. 75
3. 100
4. 25

Answer: 1. 50

Question 13. In forward biasing of the p–n junction:

1. The positive terminal of the battery is connected to p–the side and the depletion region becomes thick
2. The positive terminal of the battery is connected to n–the side and the depletion region becomes thin
3. The positive terminal of the battery is connected to n–the side and the depletion region becomes thick
4. The positive terminal of the battery is connected to p–the side and the depletion region becomes thin

Answer: 4. The positive terminal of the battery is connected to p–side and the depletion region becomes thin

Question 14. Symbolic representations of four logic gates are shown as:

Pick out which ones are for AND, NAND, and NOT gates, respectively:

1. (1) (2), (3) and (4)
2. (2) (3), (2) and (1)
3. (3) (3), (3) and (4)
4. (4) (2), (4) and (3)

Answer: 4. (4) (2), (4) and (3)

Question 15. If a small amount of pentavalent atoms is added to germanium crystal:

1. It becomes a P-type semiconductor
2. The antimony becomes an acceptor atom
3. There will be more free electrons than holes in the semiconductor
4. Its resistance is increased

Answer: 3. There will be more free electrons than holes in the semiconductor

Question 16. Two ideal diodes are connected to a battery as shown in the circuit. The current supplied by the battery is:

1. 0.75 A
2. Zero
3. 0.25 A
4. 0.5 A

Answer: 4. 0.5 A

Question 17. In a CE transistor amplifier, the audio signal voltage across the collector resistance of 2k is 2V. If the base resistance is 1k and the current amplification of the transistor is 100, the input signal voltage is:

1. 0.1 V
2. 1.0 V
3. 1 mV
4. 10 mV

Answer: 4. 10 mV

Question 18. C and Si both have the same lattice structure, having 4 bonding electrons in each. However, C is an insulator where as Si is intrinsic semiconductor. This is because:

1. In the case of C the valence band is not filled at absolute zero temperature.
2. In the case of C the conduction band is partly filled even at absolute zero temperature.
3. The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si, they lie in the third.
4. The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit.

Answer: 3. The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si, they lie in the third.

Question 19. Transfer characteristics [output voltage (V 0) vs input voltage (Vi )] for a base-biased transistor in CE configuration are shown in the figure. For using a transistor as a switch, it is used:

1. In region 3
2. Both in the region (1) and (3)
3. In region 2
4. In region 1

Answer: 2. Both in regions (1) and (3)

Question 20. The figure shows a logic circuit with two inputs A and B and the output C. The voltage waveforms across A, B, and C are as given. The logic circuit gate is:

1. OR gate
2. NOR gate
3. AND gate
4. NAND gate

Answer: 1. OR gate

Question 21. The input resistance of a silicon transistor is 100Ω. Base current is changed by 40 mA which results in a change in collector current by 2 mA. This transistor is used as a common emitter amplifier with a load resistance of 4 KΩ. The voltage gain of the amplifier is:

1. 2000
2. 3000
3. 4000
4. 1000

Answer: 1. 2000

Question 22. To get an output Y = 1 in a given circuit which of the following inputs will be correct:

Answer: 2.

Question 23. In a n-type semiconductor, which of the following statement is true:

1. Electrons are minority carriers and pentavalent atoms are dopants.
2. Holes are minority carriers and pentavalent atoms are dopants.
3. Holes are majority carriers and trivalent atoms are dopants.
4. Electrons are majority carriers and trivalent atoms are dopants.

Answer: Holes are minority carriers and pentavalent atoms are dopants.

Question 24. In a common emitter (CE) amplifier having a voltage gain of G, the transistor used has a transconductance of 0.03 mho and a current gain of 25. If the above transistor is replaced with another one with a transconductance of 0.02 mho and a current gain of 20, the voltage gain will be:

1. 1.5 G
2. \(\frac{1}{3} G\)
3. \(\frac{5}{4} G\)
4. \(\frac{2}{3} G\)

Answer: 4. \(\frac{2}{3} G\)

Question 25. The output(X) of the logic circuit shown in the figure will be:

1. \(X=\overline{A \cdot B}\)
2. X = A.B
3. \(X=\overline{A+B}\)
4. \(X=\overline{\bar{A}}, \overline{\bar{B}}\)

Answer: 2. X = A.B

Question 26. The given graph represents the V- I characteristic of a semiconductor device.

Which of the following statements is correct?

1. It is a V – I characteristic for solar cells where point A represents open circuit voltage and point B short circuit current.
2. It is for a solar cell and points A and B represent open circuit voltage and current, respectively.
3. It is for a photodiode and points A and B represent open circuit voltage and current respectively.
4. It is for an LED and points A and B represent open circuit voltage and short circuit current, respectively.

Answer: 1. It is a V – I characteristic for solar cells where point A represents open circuit voltage and point B short circuit current.

Question 27. The barrier potential of a p-n junction depends on:

1. Type of semiconductor material
2. Amount of doping
3. Temperature

Which one of the following is correct?

1. (1) and (2) only
2. (2) only
3. (2) and (3) only
4. (1), (2), and (3)

Answer: 4. (1), (2) and (3)

Question 28. Which logic gate is represented by the following combination of logic gates?

1. NAND
2. AND
3. NOR
4. OR

Answer: 2. AND

Question 29. To get output 1 for the following circuit, the correct choice for the input is:

1. A = 1, B = 0, C = 1
2. A = 0, B = 1, C = 0
3. A = 1, B = 0, C = 0
4. A = 1, B = 1, C = 0

Answer: 1. A = 1, B = 0, C = 1

Question 30. Consider the junction diode as ideal. The value of current flowing through AB is:

1. 10–3 A
2. 0 A
3. 10–2 A
4. 10–1 A

Answer: 3. 10–2 A

Question 31. An NPN transistor is connected in a common emitter configuration in a given amplifier. A load resistance of 800 is connected in the collector circuit and the voltage drop across it is 0.8 V. If the current amplification factor is 0.96 and the input resistance of the circuit is 192, the voltage gain and the power gain of the amplifier will respectively be:

1. 4,3.69
2. 4,3.84
3. 3.69, 3.84
4. 4, 4

Answer: 2. 4,3.84

Question 32. The given electrical network is equivalent to

1. AND gate
2. OR gate
3. NOR gate
4. NOT gate

Answer: 3. NOR gate

Question 33. In a common emitter transistor amplifier, the audio signal voltage across the collector is 3V. The resistance of the collector is 3k. If the current gain is 100 and the base resistance is 2k, the voltage and power gain of the amplifier are:

1. 200 and 1000
2. 15 and 200
3. 150 and 15000
4. 20 and 2000

Answer: 3. 150 and 15000

Question 34. Which one of the following represents the forward bias diode?

Answer: 1.

Question 35. In the circuit shown in the figure, the input voltage Vi is 20 V, VBE = 0, and VCE = 0. The values of I B, I C and are given by

1. IB = 40 IA, IC = 10 mA, β = 250
2. IB = 40 IA, IC = 5 mA, β= 125
3. IB = 20 IA, IC = 5 mA, β = 250
4. IB = 25 IA, IC = 5 mA, β= 200

Answer: 2. IB = 40 IA, IC = 5 mA, β= 125

Question 36. In a p-n junction diode, change in temperature due to heating

1. Affects only reverse resistance
2. Affects the overall V – I characteristics of p-n junction
3. Does not affect the resistance of the p-n junction
4. Affects only forward resistance

Answer: 2. Affects the overall V – I characteristics of p-n junction

Question 37. In the combination of the following gates the output Y can be written in terms of inputs A and B as

1. \(\overline{A \cdot B}\)
2. \(\overline{A+B}\)
3. \(\overline{A \cdot B}+A \cdot B\)
4. \(\text { A. } \bar{B}+\bar{A} \cdot B\)

Answer: 4. \(\text { A. } \bar{B}+\bar{A} \cdot B\)

Question 38. For a p-type semiconductor, which of the following statements is true?

1. Electrons are the majority carriers and pentavalent atoms are the dopants.
2. Electrons are the majority carriers and trivalent atoms are the dopants.
3. Holes are the majority carriers and trivalent atoms are the dopants.
4. Holes are the majority carriers and pentavalent atoms are the dopants.

Answer: 3. Holes are the majority carriers and trivalent atoms are the dopants.

Question 39. The correct Boolean operation represented by the circuit diagram drawn is:

1. NOR
2. AND
3. OR
4. NAND

Answer: 4. NAND

Question 40. An LED is constructed from a p-n junction diode using GaAsP. The energy gap is 1.9 eV. The wavelength of the light emitted will be equal to

1. 10.4 x 10–26 m
2. 654 nm
3. 654 Å
4. 654 x 10–11 m

Answer: 1. NAND

Question 41. The circuit diagram shown here corresponds to the logic gate.

1. NOR
2. AND
3. OR
4. NAND

Answer: 4. NAND

Question 42. Out of the following which one is a forward-biased diode?

Answer: 4.

Question 43. A n-p-n transistor is connected in a common emitter configuration (see figure) in which the collector voltage drop across load resistance (800 ) connected to the collector circuit is 0.8 V. The collector current is:

1. 2 mA
2. 0.1 mA
3. 1 mA
4. 0.2 Ma

Answer: 3. 1 mA

Question 44. Which of the following gates is called a universal gate?

1. OR gate
2. AND gate
3. NAND gate
4. NOT gate

Answer: 3. NAND gate

Question 45. An intrinsic semiconductor is converted into an n-type extrinsic semiconductor by doping it with

1. Phosphorous
2. Aluminium
3. Silver
4. Germanium

Answer: 1. Phosphorous

Question 46. The increase in the width of the depletion region in a p-n junction diode is due to:

1. Increase in forward current
2. Forward bias only
3. Reverse bias only
4. Both forward bias and reverse bias

Answer: 3. Reverse bias only

Question 47. For transistor action which of the following statements is correct?

1. The base region must be very thin and lightly doped.
2. Base, emitter, and collector regions should have the same doping concentration
3. Base, emitter, and collector regions should have the same size
4. Both the emitter junction as well as the collector junction are forward-biased

Answer: 1. The base region must be very thin and lightly doped.

Question 48. The electron concentration in an n-type semiconductor is the same as the hole concentration in a p-type semiconductor. An external field (electric) is applied across each of them. Compare the currents in them

1. Current in p-type > current in n-type
2. Current in n-type > current in p-type
3. No current will flow in p-type, current will only flow in n-type
4. Current in n-type = current in p-type

Answer: 2. Current in n-type > current in p-type

Question 49. Consider the following Statements (1) and (2) and identify the correct answer.

1. A zener diode is connected in reverse bias when used as a voltage regulator.
2. The potential barrier of the p-n junction lies between 0.1 V to 0.3 V
3. (1) and (2) both are incorrect
4. (1) is correct and (2) is incorrect
5. (1) is incorrect but (2) is correct
6. (1) and (2) both are correct

Answer: 2. (1) is correct and (2) is incorrect

Chapter 6 Solids And Semiconductors Devices Multiple Choice Questions Part – 2 Aims Question (Previous Years)

Question 1. In the following common emitter configuration, an NPN transistor with a current gain = 100 is used. The output voltage of the amplifier will be

1. 10 mV
2. 0.1 V
3. 1.0 V
4. 10 V

Answer: 3. 1.0 V

Question 2. The temperature (T) dependence of the resistivity of a semiconductor is represented by

Answer: 3.

Question 3. Which logic gate is represented by the following combination of logic gates?

1. OR
2. NAND
3. AND
4. NOR

Answer: 3. AND

Question 4. A transistor connected at common emitter mode contains a load resistance of 5 k and an input resistance of 1 k. If the input peak voltage is 5 mV and the current gain is 50, find the voltage gain.

1. 250
2. 500
3. 125
4. 50

Answer: 1. 250

Part – 3: Jee (Main) Or Aieee Problems (Previous Years)

Question 1. The logic circuit shown below has the input waveforms ‘A’ and ‘B’ as shown. Pick out the correct output waveform.

Answer: 4.

Question 2. A p-n junction (D) shown in the figure can act as a rectifier. An alternating current source (V) is connected to the circuit.

Answer: 2.

Question 3. The output of an OR gate is connected to both the inputs of a NAND gate. The combination will serve as a:

1. NOT gate
2. NOR gate
3. AND gate
4. OR gate

Answer: 2. NOR gate

Question 4. The truth table for a system of four NAND gates as shown in the figure is:

Answer: 1.

Question 5. The forward-biased diode connection is

Answer: 1.

Question 6. The temperature dependence of resistances of Cu and undoped Si in the temperature range 300 – 400 K, is best described by:

1. Linear increase for Cu, exponential increase for Si
2. Linear increase for Cu, exponential decrease for Si
3. Linear decrease for Cu, linear decrease for Si
4. Linear increase for Cu, linear increase for Si

Answer: 2. Linear increase for Cu, exponential decrease for Si

Question 7. If a,b,c,d are inputs to a gate and x is its output, then, as per the following time graph, the gate is:

1. AND
2. OR
3. NAND
4. NOT

Answer: 2. OR

Question 8. Identify the semiconductor devices whose characteristics are given below, in the order (1),(2),(3),(4)

1. Zener diode, simple diode, Light dependent resistance, Solar cell
2. Solar cell, Light dependent resistance, Zener diode, simple diode
3. Zener diode, Solar cell, Simple diode, Light dependent resistance
4. Simple diode, Zener diode, Solar cell, Light dependent resistance.

Answer: 4. Simple diode, Zener diode, Solar cell, Light-dependent resistance.

Question 9. For a common emitter configuration, if α and β have their usual meanings, the incorrect relationship between α and β is.

1. \(\alpha=\frac{\beta}{1-\beta}\)
2. \(\alpha=\frac{\beta}{1+\beta}\)
3. \(\alpha=\frac{\beta^2}{1+\beta^2}\)
4. \(\frac{1}{\alpha}=\frac{1}{\beta}+1\)

Answer: 1.

1. \(\alpha=\frac{\beta}{1-\beta}\)
2. \(\alpha=\frac{\beta^2}{1+\beta^2}\)

Question 10. In a common emitter amplifier circuit using an n-p-n transistor, the phase difference between the input and the output voltages will be:

1. 180°
2. 45°
3. 90°
4. 135°

Answer: 1. 180°

Question 11. The reading of the ammeter for a silicon diode in the given circuit is:

1. 11.5mA
2. 13.5 mA
3. 0
4. 15 mA

Answer: 1. 11.5mA

Question 12. The mobility of electrons in a semiconductor is defined as the ratio of their drift velocity to the applied electric field. If, for an n-type semiconductor, the density of electrons is 1019 m-3 and their mobility is 1.6 m2/(V.s) then the resistivity of the semiconductor (since it is an n-type semiconductor (since it is an n-type semiconductor contribution of holes is ignored) is close to:

1. 4Ωm
2. 0.4Ωm
3. 0.2Ωm
4. 2Ωm

Answer: 2. 0.4Ωm

Question 13. Ge and Si diodes start conducting at 0.3 V and 0.7 V respectively. In the following figure if the Ge diode connection is reversed, the value of V0 changes by: (assume that the Ge diode has a large breakdown voltage)

1. 0.6 V
2. 0.2 V
3. 0.4 V
4. 0.8 V

Answer: 3. 0.4 V

Question 14. To get output ‘1’ at R, for the given logic gate circuit the input values must be:

1. X = 1, Y = 1
2. X = 0, Y = 0
3. X = 0, Y = 1
4. X = 1, Y = 0

Answer: 4. X = 1, Y = 0

Question 15. For the circuit shown below, the current through the Zener diode is:

1. 14 mA
2. 9 mA
3. Zero
4. 5 mA

Answer: 2. 9 mA

Question 16. The circuit shown below contains two ideal diodes, each with a forward resistance of 50Ω. If the battery voltage is 6 V, the current through the 100Ω resistance (in Amperes) is:

1. 0.020
2. 0.030
3. 0.027
4. 0.036

Answer: 1. 0.020

Question 17. In the given circuit the current through the Zener Diode is close to:

1. 0.0 mA
2. 6.7 mA
3. 6.0 mA
4. 4.0 mA

Answer: 1. 0.0 mA

Question 18. In the figure, given that supply can vary from 0 to 5.0 V, VCC= 5V,βdc= 200, RB= 100 kΩ, RC= 1 kΩ, and VBE= 1.0 V. The minimum base current and the input voltage at which the transistor will go to saturation will be, respectively:

1. 25μA and 2.8 V
2. 20μA and 3.5 V
3. 20μA and 2.8 V
4. 25μA and 3.5 V

Answer: 4. 25μA and 3.5 V

Question 19. The output ofthe given logic circuit is:

1. \(A \bar{B}+\bar{A} B\)
2. \(\overline{\mathrm{A}} \mathrm{B}\)
3. \(A \bar{B}\)
4. \(\mathrm{AB}+\overline{\mathrm{AB}}\)

Answer: 3. \(A \bar{B}\)

Chapter 6 Solids And Semiconductors Devices Multiple Choice Questions Self Practice Paper

Question 1. In the circuit shown in the figure, A.C. of peak value 200 volts is being rectified. As compared to the resistance R, the diode resistance is negligible, the r.m.s. value of potential across the R in volts will be approximately_____

1. 200
2. 100
3. \(\frac{200}{\sqrt{2}}\)
4. 280

Answer: 2. 100

Question 2. A semiconductor X is made by doping a germanium crystal with arsenic (Z = 33). A second semiconductor Y is made by doping germanium with indium (Z = 49). The two are joined end to end and connected to a battery as shown. Which of the following statements is correct_____

1. X is p-type, Y is n-type and the junction is forward biased.
2. X is n-type, Y is p-type and the junction is forward biased.
3. X is p-type, Y is n-type and the junction is reverse-biased.
4. X is n-type, Y is p-type and the junction is reverse-biased.

Answer: 4. X is n-type, Y is p-type, and the junction is reverse-biased.

Question 3. In the following figure, a battery of 2 volts is connected between A and B. It is assumed that the resistance of a diode is zero in forward bias and infinite in reverse bias. If the positive terminal of the battery is connected to A, then the current flowing in the circuit will be________

1. 0.1 A
2. 0.2 A
3. 0.3 A
4. Zero

Answer: 2. 0.2 A

Question 4. The reverse current in a P- N junction diode at low reverse voltage is 25µA. The value of forward current at a forward voltage of 0.05 V will be if \(\frac{K T}{e}=0.025\) Volt_______

1. 16 mA
2. 1.6 mA
3. 0.16 mA
4. 160 mA

Answer: 3. 0.16 mA