831 + Interview Questions in SEMICONDUCTORS IN GENERAL AWARENESS Page 8 InterviewSolution

351.	What is thermistor?
Answer» Thermistor is a temperature sensitive resistor. Its resistance changes with change in its temperature.

Discussion

352.	In given diagram which p-n junction in reverse biasedA. B. C. D.
Answer» Correct Answer - B

Discussion

353.	The current obtained from a simple filterless reactifier isA. varying direct currentB. constant direct currentC. direct current mixed with alternating currentD. eddy current
Answer» Correct Answer - C

Discussion

354.	When out put current is in one direction only, but is continuously varying in value, then it is calledA. anode currentB. direction currentC. alternating currentD. pulsating direct current
Answer» Correct Answer - D

Discussion

355.	Enlist any two features of thermistor.
Answer» 1. A small change in surrounding temperature causes a large change in their resistance. 2. They can measure temperature variations of a small area due to their small size.

355.

Enlist any two features of thermistor.

Answer»

1. A small change in surrounding temperature causes a large change in their resistance.

2. They can measure temperature variations of a small area due to their small size.

Discussion

356.	Write a note on: i. Electric devices ii. Electronic devices
Answer» i. Electric devices: 1. These devices convert electrical energy into some other form. 2. Examples: Fan, refrigerator, geyser etc. Fan converts electrical energy into mechanical energy. A geyser converts it into heat energy. 3. They use good conductors (mostly metals) for conduction of electricity. 4. Common working range of currents for electric circuits is milliampere (mA) to ampere. 5. Their energy consumption is also moderate to high. A typical geyser consumes about 2.0 to 2.50 kW of power. 6. They are moderate to large in size and are costly. ii. Electronic devices: 1. Electronic circuits work with control or sequential changes in current through a cell. 2. A calculator, a cell phone, a smart watch or the remote control of a TV set are some of the electronic devices. 3. Semiconductors are used to fabricate such devices. 4. Common working range of currents for electronic circuits it is nano-ampere to µA. 5. They consume very low energy. They are very compact, and cost effective.

356.

Write a note on: i. Electric devices ii. Electronic devices

Answer»

i. Electric devices:

1. These devices convert electrical energy into some other form.

2. Examples: Fan, refrigerator, geyser etc. Fan converts electrical energy into mechanical energy. A geyser converts it into heat energy.

3. They use good conductors (mostly metals) for conduction of electricity.

4. Common working range of currents for electric circuits is milliampere (mA) to ampere.

5. Their energy consumption is also moderate to high. A typical geyser consumes about 2.0 to 2.50 kW of power.

6. They are moderate to large in size and are costly.

ii. Electronic devices:

1. Electronic circuits work with control or sequential changes in current through a cell.

2. A calculator, a cell phone, a smart watch or the remote control of a TV set are some of the electronic devices.

3. Semiconductors are used to fabricate such devices.

4. Common working range of currents for electronic circuits it is nano-ampere to µA.

5. They consume very low energy. They are very compact, and cost effective.

Discussion

357.	Current through a reverse biased p-n junction, increases abruptly at : (A) Breakdown voltage (B) 0.0 V (C) 0.3 V (D) 0.7 V
Answer» Correct answer is (A) Breakdown voltage

Discussion

358.	The energy levels of holes are : (A) in the valence band (B) in the conduction band(C) in the band gap but close to valence band (D) in the band gap but close to conduction band
Answer» Correct answer is (C) in the band gap but close to valence band

Discussion

359.	When the resistance between p and n regions is very high then the p-n junction diode acts asA. an inductorB. a transistorC. a capacitorD. zener diode
Answer» Correct Answer - C

Discussion

360.	Electric conduction through a semiconductor is due to : (A) Electrons (B) holes (C) none of these (D) both electrons and holes
Answer» Correct answer is (D) both electrons and holes

Discussion

361.	In a p - n junction, electric conduction takes place due toA. driftB. diffusionC. drift and diffusionD. barrier potential
Answer» Correct Answer - C

Discussion

362.	In the circuit shown infigure, voltage `V_(0)` is,A. 11.7 voltB. 11.3 voltC. 0D. None of these
Answer» Correct Answer - A

Discussion

363.	In the given circuit `V_(O_(1))&V_(O_(2))` areA. 11.3 V 0.3 VB. 0.3 V & 11.3 VC. 11.3 V & 11.3 VD. 0.3 V & 0.3 V
Answer» Correct Answer - A

Discussion

364.	The current obtained from a simple filterless reactifier isA. an eddy currentB. sinusoidal currentC. varying direct currentD. constant direct current
Answer» Correct Answer - C

Discussion

365.	Can we take one slab of p-type semiconductor and physically join it to another n-type semiconductor to get p-n junction?
Answer» 1. No. Any slab, howsoever flat, will have roughness much larger than the inter-atomic crystal spacing (~2 to 3 Å). 2. Hence, continuous contact at the atomic level will not be possible. The junction will behave as a discontinuity for the flowing charge carriers.

365.

Can we take one slab of p-type semiconductor and physically join it to another n-type semiconductor to get p-n junction?

Answer»

1. No.

Any slab, howsoever flat, will have roughness much larger than the inter-atomic crystal spacing (~2 to 3 Å).

2. Hence, continuous contact at the atomic level will not be possible. The junction will behave as a discontinuity for the flowing charge carriers.

Discussion

366.	Which is the correct diagram of a half- wave reactifier?A. B. C. D.
Answer» Correct Answer - B

Discussion

367.	In the diagram, the input is across the terminals `A` and `C` and the output is across the terminals `B` and `D`, then the outputs is A. ZeroB. same as inputC. full wave rectifierD. half wave rectifier
Answer» Correct Answer - C

Discussion

368.	In the half-wave rectifier circuit shown. Which one of the following wave forms in true for `V_(CD)`, if the input is as shown?A. B. C. D.
Answer» Correct Answer - B

Discussion

369.	In a half wave rectifier, the r.m.s value of the A.C. component of the wave isA. less than zeroB. less than D.C. ValueC. equal to D.C. valueD. greater than D.C. value
Answer» Correct Answer - D

Discussion

370.	Can we take one slab of p - type semiconductor and physically join it to another n - type semiconductor to get p - n junction?
Answer» Correct Answer - A No. Any slab will have some roughness . Hence continous contact at the atomic level will not be possible. For the charge carries , the junction will behave as a discontinuity .

Discussion

371.	The diode is also used asA. an amplifierB. a modulatorC. a rectifierD. an oscillator
Answer» Correct Answer - C

Discussion

372.	When two semiconductor of p and n type are brought in to contact, they from a p-n junction which acts like a :-A. rectifierB. amplifierC. oscillatorD. conductor
Answer» Correct Answer - A

Discussion

373.	A rectifier is used to convertA. high current into low currentB. low current into high currentC. D.C. current into A.C. currentD. A.C. current into D.C. current
Answer» Correct Answer - D

Discussion

374.	Which of the statements given in above example is true for p - type semiconductors ?
Answer» Correct Answer - A (d) Holes are majority carries and trivalent atoms are the dopants in an p - type semiconductors

Discussion

375.	In an n- type silicon, which of the following statements is true ? (a) Electrons are majority carries and trivalent atoms are the dopants. (b) Electrons are majority carries and pentavalent atoms are the dopants. (c ) Holes are minority carries and paentavalent atoms are the dopants. (d) Holes are minority carries and trivalent atoms are the dopants.
Answer» Correct Answer - A ( c) Holes are minority charge carries and pentavalent atoms are the dopants in an n- type silicon.

Discussion

376.	When two semiconductor of p and n type are brought in to contact, they from a p-n junction which acts like a :-A. conductorB. oscillatorC. amplifierD. rectifier
Answer» Correct Answer - D

Discussion

377.	In a crystal, the permitted energy states of electrons are presentA. in the conduction band and the forbidden gapB. only in the forbidden gapC. in the valence band and conduction bandD. in the forbidden gap and the valence band
Answer» Correct Answer - C

Discussion

378.	In N-Type semiconductors, which extra energy level is added?(a) Conduction level(b) Donor Energy Level(c) Acceptor energy level(d) Valence level
Answer» Correct option is (b) Donor Energy Level Best explanation: In N-Type semiconductor level, a new energy level below the conduction band is formed. The energy difference between the two is about 0.045 eV.

Discussion

379.	What are the current carriers in semiconductors?(a) Electrons and Protons(b) Electrons and Nucleons(c) Electrons and Photons(d) Electrons and Holes
Answer» Right choice is (d) Electrons and Holes To explain I would say: Electrons and holes are the two current carriers in semiconductors. Electrons are negatively charged while holes are positively charged. Their movement gives rise to a current in the semiconductor.

Discussion

380.	The electrons in the atoms of an element, which determine its chemical and electricalproperties are calledA. valence electronsB. conduction electronsC. free electronsD. bound electrons
Answer» Correct Answer - A

Discussion

381.	The concentration of doping is kept below ______________(a) 1 %(b) 5 %(c) 10 %(d) 50 %
Answer» The correct choice is (a) 1 % Easiest explanation: The concentration of doping in semiconductors is generally kept below 1 %. However, it is enough to bring a huge drop in the energy gap.

Discussion

382.	In a semi conductor diode , the barrier potential offers opposition to only -A. majority carrier in both regionsB. minority carrier in both regionsC. free electrons in the n-regionD. holes in the p-region
Answer» Correct Answer - C In a semiconductor diode, the barrier potential offers opposition to only free electrons in the n-region.

Discussion

383.	What is the order of forbidden energy gap in `eV` in the energy bands of silicon ?A. 0.5 eVB. 1.1 eVC. 2.1 eVD. 3.5 eV
Answer» Correct Answer - B

Discussion

384.	Which one of the following is not an intrinsic semiconductor?(a) Carbon(b) Silicon(c) Germanium(d) Lead
Answer» Right answer is (a) Carbon Easiest explanation: There are 4 bonding electrons in all the above materials. However, the energy required to take out an electron will be maximum for carbon as the valence electrons are in the second orbit. Hence, the number of free electrons for conduction is negligibly small in C.

Discussion

385.	Pure Si at 300 K has equal electron (ni) and hole concentration (p) of 1.5 X 10^16 m^-3. Doping by indium increases p to 4.5 X 10^22 m^-3. What is n in the doped silicon?(a) 4.5 X 10^9 m^-3(b) 4.5 X 10^22 m^-3(c) 5 X 10^9 m^-3(d) 5 X 10^22 m^-3
Answer» The correct choice is (c) 5 X 10^9 m^-3 Best explanation: Here, ni = 1.5 X 10^16 m^-3, p = 4.5 X 10^22 m^-3 We know, np = ni^2 n = ni^2/p = 5 X 10^9 m^-3.

Discussion

386.	The following graph depicts the I-V characteristics of which instrument?(a) Photodiode(b) Light Emitting Diode(c) Solar Cell(d) Zener diode
Answer» Right answer is (c) Solar Cell Easiest explanation: The generation of EMF by a solar cell is due to three basic processes: generation of electron-hole pair, separation of electrons and holes and collection of electrons by the front contact. The p-side becomes positive and the n-side becomes negative giving rise to photo voltage. The I-V characteristics of the solar cell are drawn in the fourth quadrant of the coordinate axis because a solar cell does not draw current but supplies the same to the load.

Discussion

387.	Identify the type of material.(a) Intrinsic Semiconductor(b) N-Type semiconductor(c) P-Type semiconductor(d) Conductor
Answer» Correct choice is (c) P-Type semiconductor The explanation is: In the figure, as we can see there is an acceptor energy level just above the valence band. This happens in the case of P-Type semiconductors.

Discussion

388.	Which of the following can be used to create a P-Type Semiconductor?(a) P(b) Sb(c) Ga(d) As
Answer» The correct choice is (c) Ga To explain: For a P-Type semiconductor, a material with 3 valence electrons is chosen. Out of the given choices, Ga can be used to create a P-Type Semiconductor.

Discussion

389.	Which of the following is n-type semiconductor?(a) CaO(b) MgO(c) ZnO(d) BaO
Answer» Right answer is (c) ZnO The explanation: II-VI semiconductors are generally p-type semiconductors except for ZnO and ZnTe. II-VI semiconductors are those which contain atoms of materials that have 2 valence electrons and 6 valence electrons.

Discussion

390.	The Hall coefficient of a specimen is 3.66 x 10^-4 m^3C^-1. If it’s resistivity is 8.93 x 10^-3 Ωm, what will be its mobility?(a) 0.01 m^2V^-1s^-1(b) 0.02 m^2V^-1s^-1(c) 0.03 m^2V^-1s^-1(d) 0.04 m^2V^-1s^-1
Answer» The correct choice is (d) 0.04 m^2V^-1s^-1 Easy explanation: We know, Mobility = Hall coefficient/resistivity Therefore, Mobility = 3.66 x 10^-4/8.93 x 10^-3 = 0.04 m^2V^-1s^-1.

Discussion

391.	Resistivity of a semiconductor depends onA. sizeB. type of atomsC. lengthD. size and type of atom
Answer» Correct Answer - B

Discussion

392.	In common base circuit of a transistor , current amplification factor is `0.95`. Calculate the emitter current , if base current is `0.2` mAA. 2 mAB. 4 mAC. 6 mAD. 8 mA
Answer» Correct Answer - B `alpha=0.95 = I_C/I_E` and `I_E=I_C-I_B " " therefore I_C=I_E+I_B` `therefore I_C=0.95 I_E` Thus `I_E+I_B=0.95I_E` `therefore I_E(1-0.95) = -I_B` `therefore I_E(5/100)=2/10 mA ` (-ve sign neglected) `50I_E=200 " " therefore I_E=4mA`

Discussion

393.	The current through the diode in the given circuit is A. 1 mAB. 10 mAC. 5 mAD. zero
Answer» Correct Answer - D Current is zero as the junction diode is reverse biased.

Discussion

394.

Distinguish between p-type and n-type semiconductor.

Answer»

p-type semiconductor	n-type semiconductor
1. The impurity of some trivalent element like B, Al, In, etc. is mixed with semiconductor.	The impurity of some pentavalent element like P, As, Sb, etc. is mixed
2. The impurity atom accepts one electron hence the impurities	The impurity atom donates – one electron, hence the impurities added are known as donor impurities.
3. The holes are majority charge carriers and electrons are minority charge carriers.	The electrons are j majority charge carriers and holes are minority charge carriers.
4. The acceptor energy level is close to the valence band and far away from conduction band.	Donor energy level is close to the conduction band and far away from valence band.

Discussion

395.	What is the charge on a p-type and n-type semiconductor?
Answer» n-type as well as p-type semiconductors are electrically neutral.

Discussion

396.	What is a p-n junction?
Answer» When n-type and p-type semiconductor materials are fused together, the junction formed is called as p-n junction.

Discussion

397.	In a PNP transistor, N-type semiconductor is used as theA. collector onlyB. base onlyC. emitter onlyD. collector or emitter
Answer» Correct Answer - B

Discussion

398.	In p-type semiconductor, the major charge carriers are:A. neutronsB. protonsC. electronsD. holes
Answer» Correct Answer - D The trivalent impurities provide holes to create positive charge carriers. It is known that in a p-type semiconductor trivalent impurity (having 3 valance electrons) is added. Hence, current carriers in p-type semiconductors are holes.

Discussion

399.	GaAs is-A. an elemental semiconductorB. alloy semiconductorC. bad conductorD. metallic semiconductor
Answer» Correct Answer - B Holes behave as positive charge carriers, electrons have negative charge. Thus, gallium Arsenide is an alloy semiconductor where Ga contributes holes and as contributes electrons.

Discussion

400.	The current (I) in the circuit will be:-A. `(5)/(40)A`B. `(5)/(50)A`C. `(5)/(10)A`D. `(5)/(20)A`
Answer» Correct Answer - B

Discussion

Explore topic-wise InterviewSolutions in .

What is thermistor?

In given diagram which p-n junction in reverse biasedA. B. C. D.

The current obtained from a simple filterless reactifier isA. varying direct currentB. constant direct currentC. direct current mixed with alternating currentD. eddy current

When out put current is in one direction only, but is continuously varying in value, then it is calledA. anode currentB. direction currentC. alternating currentD. pulsating direct current

Enlist any two features of thermistor.

Write a note on: i. Electric devices ii. Electronic devices

Current through a reverse biased p-n junction, increases abruptly at : (A) Breakdown voltage (B) 0.0 V (C) 0.3 V (D) 0.7 V

The energy levels of holes are : (A) in the valence band (B) in the conduction band(C) in the band gap but close to valence band (D) in the band gap but close to conduction band

When the resistance between p and n regions is very high then the p-n junction diode acts asA. an inductorB. a transistorC. a capacitorD. zener diode

Electric conduction through a semiconductor is due to : (A) Electrons (B) holes (C) none of these (D) both electrons and holes

In a p - n junction, electric conduction takes place due toA. driftB. diffusionC. drift and diffusionD. barrier potential

In the circuit shown infigure, voltage `V_(0)` is,A. 11.7 voltB. 11.3 voltC. 0D. None of these

In the given circuit `V_(O_(1))&V_(O_(2))` areA. 11.3 V 0.3 VB. 0.3 V & 11.3 VC. 11.3 V & 11.3 VD. 0.3 V & 0.3 V

The current obtained from a simple filterless reactifier isA. an eddy currentB. sinusoidal currentC. varying direct currentD. constant direct current

Can we take one slab of p-type semiconductor and physically join it to another n-type semiconductor to get p-n junction?

Which is the correct diagram of a half- wave reactifier?A. B. C. D.

In the diagram, the input is across the terminals `A` and `C` and the output is across the terminals `B` and `D`, then the outputs is A. ZeroB. same as inputC. full wave rectifierD. half wave rectifier

In the half-wave rectifier circuit shown. Which one of the following wave forms in true for `V_(CD)`, if the input is as shown?A. B. C. D.

In a half wave rectifier, the r.m.s value of the A.C. component of the wave isA. less than zeroB. less than D.C. ValueC. equal to D.C. valueD. greater than D.C. value

Can we take one slab of p - type semiconductor and physically join it to another n - type semiconductor to get p - n junction?

The diode is also used asA. an amplifierB. a modulatorC. a rectifierD. an oscillator

When two semiconductor of p and n type are brought in to contact, they from a p-n junction which acts like a :-A. rectifierB. amplifierC. oscillatorD. conductor

A rectifier is used to convertA. high current into low currentB. low current into high currentC. D.C. current into A.C. currentD. A.C. current into D.C. current

Which of the statements given in above example is true for p - type semiconductors ?

When two semiconductor of p and n type are brought in to contact, they from a p-n junction which acts like a :-A. conductorB. oscillatorC. amplifierD. rectifier

In a crystal, the permitted energy states of electrons are presentA. in the conduction band and the forbidden gapB. only in the forbidden gapC. in the valence band and conduction bandD. in the forbidden gap and the valence band

In N-Type semiconductors, which extra energy level is added?(a) Conduction level(b) Donor Energy Level(c) Acceptor energy level(d) Valence level

What are the current carriers in semiconductors?(a) Electrons and Protons(b) Electrons and Nucleons(c) Electrons and Photons(d) Electrons and Holes

The electrons in the atoms of an element, which determine its chemical and electricalproperties are calledA. valence electronsB. conduction electronsC. free electronsD. bound electrons

The concentration of doping is kept below ______________(a) 1 %(b) 5 %(c) 10 %(d) 50 %

In a semi conductor diode , the barrier potential offers opposition to only -A. majority carrier in both regionsB. minority carrier in both regionsC. free electrons in the n-regionD. holes in the p-region

What is the order of forbidden energy gap in `eV` in the energy bands of silicon ?A. 0.5 eVB. 1.1 eVC. 2.1 eVD. 3.5 eV

Which one of the following is not an intrinsic semiconductor?(a) Carbon(b) Silicon(c) Germanium(d) Lead

Pure Si at 300 K has equal electron (ni) and hole concentration (p) of 1.5 X 10^16 m^-3. Doping by indium increases p to 4.5 X 10^22 m^-3. What is n in the doped silicon?(a) 4.5 X 10^9 m^-3(b) 4.5 X 10^22 m^-3(c) 5 X 10^9 m^-3(d) 5 X 10^22 m^-3

The following graph depicts the I-V characteristics of which instrument?(a) Photodiode(b) Light Emitting Diode(c) Solar Cell(d) Zener diode

Identify the type of material.(a) Intrinsic Semiconductor(b) N-Type semiconductor(c) P-Type semiconductor(d) Conductor

Which of the following can be used to create a P-Type Semiconductor?(a) P(b) Sb(c) Ga(d) As

Which of the following is n-type semiconductor?(a) CaO(b) MgO(c) ZnO(d) BaO

The Hall coefficient of a specimen is 3.66 x 10^-4 m^3C^-1. If it’s resistivity is 8.93 x 10^-3 Ωm, what will be its mobility?(a) 0.01 m^2V^-1s^-1(b) 0.02 m^2V^-1s^-1(c) 0.03 m^2V^-1s^-1(d) 0.04 m^2V^-1s^-1

Resistivity of a semiconductor depends onA. sizeB. type of atomsC. lengthD. size and type of atom

In common base circuit of a transistor , current amplification factor is `0.95`. Calculate the emitter current , if base current is `0.2` mAA. 2 mAB. 4 mAC. 6 mAD. 8 mA

The current through the diode in the given circuit is A. 1 mAB. 10 mAC. 5 mAD. zero

Distinguish between p-type and n-type semiconductor.

What is the charge on a p-type and n-type semiconductor?

What is a p-n junction?

In a PNP transistor, N-type semiconductor is used as theA. collector onlyB. base onlyC. emitter onlyD. collector or emitter

In p-type semiconductor, the major charge carriers are:A. neutronsB. protonsC. electronsD. holes

GaAs is-A. an elemental semiconductorB. alloy semiconductorC. bad conductorD. metallic semiconductor

The current (I) in the circuit will be:-A. `(5)/(40)A`B. `(5)/(50)A`C. `(5)/(10)A`D. `(5)/(20)A`