Physics MCQs Test P 15

HN PHYSICS

Semiconductor Diode

Q1: In the forward bias arrangements of a PN junction diode

  1. The N end is connected to the positive terminal of the battery
  2. The P end is connected to the positive terminal of the battery
  3. The direction of the current is from N end to the P end in the diode
  4. The P end is connected to the negative terminal of the battery

Answer: (b) The P end is connected to the positive terminal of the battery



Q2: In a PN junction diode

  1. The current in the reverse biased condition is generally very small
  2. The current in the reverse biased condition is generally very small but the forward-biased current is independent of the bias voltage
  3. The reverse-biased current is strongly dependent on the applied bias voltage
  4. The forward biased current is very small in comparison to reverse-biased current.

Answer: (a) The current in the reverse biased condition is generally very small

Q3: The cut-in voltage for silicon diode is approximately

  1. 0.2 V
  2. 0.6 V
  3. 1.1 V
  4. 1.4 V

Answer: (b) 0.6 V

Q4: The electrical resistance of the depletion layer is large because

  1. It has no change carriers
  2. It has a large number of charge carriers
  3. It contains electrons as charge carriers
  4. It has holes as charge carriers

Answers: (a) It has no change carriers

Q5: If the forward voltage in a semiconductor diode is doubled, the width of the depletion layer will

  1. Become half
  2. Become one-fourth
  3. Remain unchanged
  4. Become double

Answer: (a) Become half

Q6: The PN junction diode is used as

  1. An amplifier
  2. A rectifier
  3. An oscillator
  4. A modulator

Answer: (b) A rectifier

Q7: When a PN junction diode is reverse biased

  1. Electrons and holes are attracted towards each other and move towards the depletion region
  2. Electrons and holes move away from the junction depletion region
  3. Height of the potential barrier decreases
  4. No change in the current takes place

Answer: (b) Electrons and holes move away from the junction depletion region

Q8: A PN junction has a thickness of the order

  1. 1 cm
  2. 1 mm
  3. 10-6 m
  4. 10-12 cm

Answer: (c) 10-6 m

Q9: In the depletion region of an unbiased PN junction diode there are

  1. Only electrons
  2. Only holes
  3. Both electrons and holes
  4. Only fixed ions

Answer: (d) Only fixed ions

Q10: On increasing the reverse bias to a large value in a PN junction diode, current

  1. Increases slowly
  2. Remains fixed
  3. Suddenly increases
  4. Decreases slowly

Answer: (c) Suddenly increases

BJT

Q1: For a transistor to operate in an active region what is the essential possible condition of biasing?

a. Collector-base and emitter-base junctions are reverse biased.

b. Collector-base junction is reverse biased and the emitter-base is forward biased

c. Collector-base and emitter-base junctions are forward biased

d. Collector-base junction is forward biased  and emitter-base is reverse biased

Answer: (b) Collector-base junction is reverse biased and the emitter-base is forward biased

Q2: Which operating region of BJT enables Emitter-base & collector-base junctions to undergo perfect short-circuit configuration?

a. Saturation Region

b. Cut-off Region

c. Active Region

d. None

Answer: (b) Saturation Region

Q3: When zero input control signal is applied which functional mode enables the BJT to act as an open switch?

a. Reversed biased mode of BE junction

b. Reversed as well as the forward-biased mode of BE junction

c. Forward biased mode of BE junction

d. None

Answer: (d) None

Q4: The power dissipated by a transistor approximately equals the collector current times.

a. Collector-emitter voltage

b. Base-emitter voltage

c. Base supply voltage

d. 0.7 V

Answer: (a) collector-emitter voltage

Q5: Which of the following leakage current causes a small collector current with zero base current

a. Collector diode

b. Base diode

c. Emitter diode

d. Transistor

Answer: (a) Collector diode

Q6: What will be the answer if we recalculate the collector-emitter voltage with the second approximation?

a. The same as the ideal value

b. Larger than the ideal value

c. Smaller than the ideal value

d. incorrect

Answer: (b) Larger than the ideal value

Q7: Will a transistor act as a closed switch by defining the requisite magnitude of saturation level with an equivalent amount of 

a. negative control voltage

b. both negative & positive control voltages

c.  positive control voltage

d. none of the above

Answer: (a) positive control voltage

Q8: Which current source is connected between collector and base terminals in order to supervise the consequences of base control in an active region DC Model of BJT?

a. αIB

b. βIB

c. αIE

d. βIE

Answer: (b) βIB

Q9: What is the collector current when the base resistor is open?

a. 1 mA

b. 2 mA

c. 0

d. 10 mA

Answer: (c) 0

Q10: For the second approximation what is the base-emitter voltage?

a. 0.3 V

b. 0.7 V

c.0

d. 1 V

Answer: (b) 0.7 V

Photodiode


Q1: Photodiode is used in the detection of

  1. Visible light
  2. Invisible light
  3. No light
  4. Both visible and invisible light

Answer: (d) Both visible and invisible light

Q2: In using a photodiode as a photodetector, it is invariably reverse biased

  1. The power consumption is much reduced compared to reverse biased condition
  2. Only when the photodiode is reverse biased the incident photons produce electron-hole pairs
  3. Only if the diode is reverse biased light variations can be converted into current variations
  4. When photons are incident on the diode, the fractional change in the reverse current is much greater than the fractional change in the forward current

Answer: (d) When photons are incident on the diode, the fractional change in the reverse current is much greater than the fractional change in the forward current.

Q3: The maximum wavelength of photons that can be detected by a photodiode made by a semiconductor of bandgap 2eV is about

  1. 620 nm
  2. 700 nm
  3. 740 nm
  4. 1240 nm

Answer: (a) 620 nm

Q4: The presence of dark current decreases the sensitivity of the photodiode to light

  1. True
  2. False

Answer: (a) True

Q5: Photodiodes operate by absorption of photons or charged particles and generate a flow of current in an external circuit,……….. to the incident power. The light is absorbed ……….with distance and is ………..to the absorption coefficient.

  1. Proportional, exponentially, proportional
  2. Proportional, logarithmically, inversely proportional
  3. Inversely proportional, exponentially, unrelated

Answer: (a) Proportional, exponentially, proportional

Q6: What is the reason phototransistor produces more current than a photodiode?

  1. A wider spectrum is accepted by the phototransistor than the photodiode
  2. The current produced by photons is amplified by the hfe of the transistor
  3. The phototransistor can heavily doped than the photodiode
  4. At low light conditions, a photodiode is used.

Answer: (c) The current produced by photons is amplified by the hfe of the transistor

Q7: In a photodiode, when there is no incident light, the reverse current is almost negligible and is called

  1. Zener current
  2. Dark current
  3. Photocurrent
  4. PIN current

Answer: (b) Dark current

Q8: Compared to a photo-diode, which of the listed advantages and disadvantages would be expected of a phototransistor

  1. Faster response and greater sensitivity
  2. Faster response and less sensitivity
  3. Slower response and greater sensitivity
  4. Slower response and less sensitivity

Answer: (c) Slower response and greater sensitivity

Q9: When a diode is forward biased, the recombination of free electron and holes produce

  1. Heat
  2. Light
  3. Radiation
  4. All the above

Answer: (d) All the above

Q10: The width of the depletion region is

  1. Directly proportional to the doping
  2. inversely proportional to the doping
  3. Independent of doping
  4. None of the above

Answer: (b) inversely proportional to the doping


PN Junction Diode

Q1: In a PN junction with no external voltage, the electric field between acceptor and donor ion is called a

  1. Peak
  2. Barrier
  3. Threshold
  4. Path

Answer: (b) Barrier

Q2: In a PN junction the potential barrier is due to the charges on either side of the junction, these charges are

  1. Majority carriers
  2. Minority carriers
  3. Both (a) and (b)
  4. Fixed donor and accepter ions

Answer: (d) Fixed donor and accepter ions

Q3: The capacitance of a reverse-biased PN junction

  1. Increases as reverse bias is increased
  2. Decreases as reverse bias is increased
  3. Increases as reverse bias is decreased
  4. Is significantly low

Answer: (c) Increases as reverse bias is decreased

Q4: For a PN junction diode, the current in reverse bias maybe

  1. Few milliamperes
  2. Between 0.2 A and 15 A
  3. Few amperes
  4. Few micro or nano amperes

Answer: (d) Few micro or nano amperes

Q5: When PN junction is in forward bias, by increasing the battery voltage

  1. Circuit resistance increases
  2. Current through P_N junction increases
  3. Current through P_N junction decreases
  4. None of the above

Answer: (b) Current through P_N junction increases

Q6: When a PN junction is reverse biased

  1. Holes and electrons tend to concentrate towards the junction
  2. The barrier tends to break down
  3. Holes and electrons tend to move away from the junction
  4. None of these

Answer: (c) Holes and electrons tend to move away from the junction

Q7: A PN junction

  1. Has low resistance in forward as well as reverse directions
  2. Has high resistance in forward as well as reverse directions
  3. Conductors in the forward direction only
  4. Conducts in the reverse direction only

Answer: (c) Conductors in the forward direction only

Q8: A PN junction is said to be forward-biased when

  1. The positive terminal of the battery is connected to P-side and the negative side to the N-side
  2. Junction is earthed
  3. N-side is connected directly to the p-side
  4. The positive terminal of the battery is connected to N-side and the negative side to the P-side.

Answer: (a) The positive terminal of the battery is connected to P-side and the negative side to the N-side

Q9: PN junction failure below 5 V is caused primarily by

  1. Avalanche breakdown
  2. Zener breakdown
  3. Either (a) or (b)
  4. None of the above

Answer: (b) Zener breakdown

Q10: In a reverse-biased PN junction, the current through the junction increases abruptly at

  1. 0.5 V
  2. 1.1 V
  3. 0.72 V
  4. Breakdown voltage

Answer: (d) Breakdown voltage

Series And Parallel Circuits

Q1: A certain circuit is composed of two parallel resistors. The total resistance is 1,403 Ω. One of the resistors is 2 Ω. The other resistor value is

  1. 1,403 Ω
  2. 4.7 kΩ
  3. 2 kΩ
  4. 3,403 Ω

Answer: (b) 4.7 kΩ

Q2: A voltage divider consists of ot two 100 kΩ resistors and a 12 V source. What will the voltage be if a load resistor of 1 MΩ is connected to the output?

  1. 0.57 V
  2. 6 V
  3. 12 V
  4. 5.7 V

Answer: (d) 5.7 V

Q3: The parallel combination of a 1.5 kΩ resistor and 470 Ω resistor is in series with the parallel combination of five 1 kΩ resistors. The source voltage is 50 V. The percentage of the load current through any single 1 kΩresistor is

  1. 25 %
  2. 20 %
  3. 100 %
  4. 50 %

Answer: (b) 20 %

Q4: On which of the following voltage range settings will a voltameter present minimum load on a circuit?

  1. 1 V
  2. 50 V
  3. 500 V
  4. 1,000 V

Answer: (d) 1,000 V

Q5: A Voltage divider consists of two 68 kΩ resistors and a 24 V source. The unknown output voltage is

  1. 12 V
  2. 24 V
  3. 0 V
  4. 6 V

Answer: (a) 12 V

Q6: Two 3.3 kΩ resistors are in series combination are in parallel with a 4.7 kΩ resistor. What will be the voltage across the 4.7 kΩ resistors if the voltage across one of the 3.3 kΩ resistors is 12 V

  1. 24 V
  2. 12 V
  3. 0 V
  4. 6 V

Answer: (a) 24 V

Q7: The 1.2 kΩ resistors are in series and this series combination is in parallel with a 3.3 3.3 kΩ resistor. The total resistance is

  1. 138 Ω
  2. 1,389 Ω
  3. 5,700 Ω
  4. 880 Ω

Answer: (b) 1,389 Ω

Q8: A certain voltage divider consists of three 1 kΩ resistors in series. Which of the following load resistors will have the least effect on the output voltage?

  1. 1 MΩ
  2. 100 kΩ
  3. 1 kΩ
  4. 330 Ω

Answer: (a) 1 MΩ

Q9: A certain Wheatstone bridge has the following resistor values: R1= 10 kΩ, R2 = 720 Ω and R4 = 2.4 kΩ. The unknown resistance is

  1. 24 Ω
  2. 2.4 Ω
  3. 300 Ω
  4. 3,000 Ω

Answer: (d) 3,000 Ω

Q10: In a certain five-step R/2R ladder network, the smallest resistor value is

  1. Indeterminable
  2. 2 kΩ
  3. 10 kΩ
  4. 20 kΩ

Answer: (b) 2 kΩ



Junction Transistor

Q1. The emitter-base junction of a transistor is ………. Biased while the collector-base junction is ………….

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

Answer: (d) Forward, reverse

Q2: A NPN transistor conducts when

  1. Both collector and emitter are positive with respect to the base
  2. Collector is positive and the emitter is negative with respect to the base
  3. Collector is positive and the emitter is at the same potential as the base
  4. Both collector and emitter are negative with respect to the base

Answer: (b) Collector is positive and the emitter is negative with respect to the base

Q3: Which of the following is true

  1. Common base transistor is commonly used because the current gain is maximum
  2. Common emitter is commonly used because the current gain is maximum
  3. Common collector is commonly used because the current gain is maximum
  4. Common emitter is the least used transistor

Answer: (b) Common emitter is commonly used because the current gain is maximum

Q4: For a common base configuration of PNP transistor Ic/IE = 0.98 then the maximum current gain in common emitter configuration will be

  1. 12
  2. 24
  3. 6
  4. 5

Answer: (b) 24

Q5: In a PNP transistor working as a common-base amplifier, the current gain is 0.96 and emitter current is 7.2 mA. The base current is

  1. 0.4 mA
  2. 0.2 mA
  3. 0.29 mA
  4. 0.35 mA

Answer: (c) 0.29 mA

Q6: Which is the least doped region in a transistor?

  1. Either emitter or collector
  2. Base
  3. Emitter
  4. Collector

Answer: (b) Base

Q7: The transistors provide good power amplification when they are used in

  1. Common collector configuration
  2. Common emitter configuration
  3. Common base configuration
  4. None of these

Answer: (b) Common emitter configuration

Q8: For a transistor the parameter b= 99. The value of the parameter is a is

  1. 0.9
  2. 0.99
  3. 1
  4. 9

Answer: (b) 0.99

Q9: A transistor is used in common emitter mode as an amplifier. Then

  1. The base-emitter junction will be forward biased
  2. The input signal is connected in series with the voltage applied to the base-emitter junction
  3. The base-emitter junction will be reversed biased
  4. The voltage applied to bias the base-collector junction and the input signal is connected in series

Answer: (b) The input signal is connected in series with the voltage applied to the base-emitter junction

Q10: In a PNP transistor the base is the N-region. Its width relative to the P-region is

  1. Smaller
  2. Larger
  3. Same
  4. Not related

Answer: (a) Smaller

 

Inductance

Q1: Mutual inductance between two magnetically coupled coils depends on

  1. Permeability of the core material
  2. Number of turns of the coils
  3. The cross-sectional area of their common core
  4. All of the above

Answer: (d) All of the above

Q2: What will be the inductance if the iron core is removed from the iron cored coil to make it air-cored coil?

  1. More
  2. Less
  3. The same
  4. None

Answer: (b) Less

Q3: Higher the self-inductance of a coil

  1. Lesser its weber-turns
  2. Emf induced is low
  3. Greater the flux produced
  4. Longer the delay in establishing a steady current through it

Answer: (d) Longer the delay in establishing a steady current through it

Q4: Which of the following circuit elements will oppose the change in circuit current?

  1. Capacitance
  2. Inductance
  3. Resistance
  4. All of the above

Answer: (b) Inductance

Q5: How does an inductor work?

  1. Storing energy as a magnetic field.
  2. A wire piece is charged
  3. Introducing resistance into a circuit
  4. Choking off high-frequency ac

Answer:(a) Storing energy as a magnetic field.

Q6: The inductance of the coil is not affected by which of the following?

  1. The length of the coil
  2. Number of turns
  3. The material of the core
  4. The diameter of the wire

.Answer: (d) The diameter of the wire.

Q7: In a small inductance:

  1. Large current flow
  2. Energy is stored and released quickly
  3. Small current flow
  4. Energy is stored and released slowly

Answer: (b) Energy is stored and released quickly

Q8: The phenomenon due to which there is an induced current in one coil due to the current in a neighbouring coil is?

  1. Mutual inductance
  2. Steady current
  3. Electromagnetism
  4. Susceptance

Answer: (a) Mutual inductance

Q9: The combination of the same two inductors (33 mH and 55 mH) connected in parallel without mutual inductance will have a value of

  1. 22 mH
  2. 88 mH
  3. 1.8 H
  4. 21 mH

Answer: (b) 88 mH.

Q10: Three inductance with the values 4 NH, 140 μH, and 5 H are connected in series without mutual inductance. For practical purposes, the net inductance will be very close to

  1. 4 NH
  2. 140 μH
  3. 5 H
  4. None of these

Answer: (c) 5 H

Ac Generator

Q1: An alternator is an electromechanical ac generator.

  1. True
  2. False

Answer: (B) False

Q2: In A.C generator increasing the no. of turns in the coil

  1. Decreases the Electromotive force (EMF)
  2. Electromotive force (EMF) remains the same
  3. Increases the Electromotive force (EMF)
  4. Electromotive force (EMF) becomes zero

Answer: (c) Increases the Electromotive force (EMF)

Q3: The Electromotive force (EMF) developed by the generator depends upon

  1. Area of rotating wire
  2. length of rotating wire
  3. Radius of wire
  4. size of magnet

Answer: (b) length of rotating wire

Q4: The metal detectors installed at airports and other places for security purpose are based on the principle of

  1. potential difference
  2. electromagnetic difference
  3. electromagnetic induction
  4. potential energy

Answer: (c) electromagnetic induction

Q5: If the coil is placed perpendicular to field lines then the number of lines passing through the coil is

  1. Minimum
  2. maximum
  3. zero
  4. maybe maximum or minimum

Answer: (b) maximum

Q6: In alternative current generator, AC current reverses its direction

  1. 10 times per second
  2. 20 times per second
  3. 60 times per second
  4. 50 times per second

Answer: (d) 50 times per second

Q7: Name two main parts of an AC generator

  1. Stator
  2. Rotor
  3. Both 1 and 2
  4. None of these

Answer: (c) Both 1 and 2

Q8: AC generator converts

  1. Mechanical energy to electrical energy
  2. Electrical energy to mechanical energy
  3. Heat energy to mechanical energy

Answer: (a) Mechanical energy to electrical energy

 

Q9: What replacement is required to convert an AC generator to DC generator?

  1. Concave magnets with horseshoe magnets
  2. Armature with coil
  3. Slip rings with split rings
  4. None of the above

Answer: Slip rings with split rings

Q10: The direction of induced emf or current is indicated by

  1. Fleming’s left-hand rule
  2. Fleming’s right-hand rule
  3. Faraday’s law of electromagnetic induction
  4. None of these

Answer: (b) Fleming’s right-hand rule

Voltage Regulator

Q1: Which of the following is considered as three-pin voltage regulator ICs?

  1. Voltage regulators which are adjustable
  2. Fixed voltage regulator
  3. Both a and b

Answer: (c) Both a and b

Q2: Which type of IC voltage regulator there is a continuous variation in the impedance of transistor in order to supply the desired amount of load current?

  1. Linear regulators
  2. Switching regulators
  3. Both a and b

Answer: (a) Linear regulators

Q3: Voltage regulators require

  1. Only line regulation
  2. Only load regulation
  3. A constant load
  4. Load and line regulation

Answer: (d) Load and line regulation

Q4: What type of regulators offer inherent short-circuit protection?

  1. Shunt regulators
  2. Series regulators
  3. Three-terminal regulators
  4. Switching regulators

Answers: (a) Shunt regulators

Q5: Voltage regulators keep a constant …………output voltage when the input or load varies within limits.

  1. DC
  2. AC
  3. ripple

Answer: (a) DC

Q6: Switching regulators are series type regulators, which has ……….power dissipation and …………efficiency.

  1. Increased, increased
  2. Increased, reduced
  3. Reduced, reduced
  4. Reduced, increased

Answer: (c) Reduced, increased

Q7: Which among the following performance parameter is called the change in line voltage within a specified range at a constant load current?

  1. Line regulation
  2. Load regulation
  3. Temperature stability factor
  4. Ripple factor

Answer: (a) Line regulation

Q8: The output voltage of a regulated power supply is affected by which of the following factors

  1. Input voltage
  2. Load current
  3. Temperature
  4. All the above

Answer: (d) All the above

Q9: Series pass transistor always operates in the………. region in a linear IC voltage regulator

  1. Active
  2. Saturation
  3. Cut-off
  4. All of these

Answer: (a) Active


0 Comments