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Objective Questions

Latest BEL Senior Assistant Engineer Exam Question (Objective Questions), MCQ in English

Subjects : Technical Subject (Electronics & Communication), General Aptitude

Question Bank BEL Senior Assistant Engineer Exam - English
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Technical Subject (Electronics & Communication)

Question 1Single Answer
Which one of the following helps experimental confirmation of the Crystalline state of matter?
  1. A
    Shock compression
  2. B
    Photo emission
  3. C
    Conductivity measurements
  4. D
    X-ray diffraction
Question 2Single Answer
The electrical conductivity of pure semiconductor is:
  1. A
    Proportional to temperature
  2. B
    Increases exponentially with temperature
  3. C
    Decreases exponentially with temperature
  4. D
    Not altered with temperature
Question 3Single Answer
Consider the following statements pertaining to the resistance of a conductor:
1. Resistance can be simply defined as the ratio of voltage across the conductor to the current through the conductor. This is, in fact, Georg Ohm’s law.
2. Resistance is a function of voltage and current.
3. Resistance is a function of conductor geometry and its conductivity
Which of the above statements are correct?
  1. A
    1 and 2 only
  2. B
    2 and 3 only
  3. C
    1 and 3 only
  4. D
    1, 2 and 3
Question 4Single Answer
The ratio of ionic radii of Cations i.e.and that of Anions i.e.for stable and unstable ceramic crystal structure, is:
  1. A
    Less than unity
  2. B
    Greater than unity
  3. C
    Unity
  4. D
    Either lesser or greater than unity
Question 5Single Answer
Which one of the following statements is correct?
  1. A
    For insulators the band-gap is narrow as compared to semiconductors
  2. B
    For insulators the band-gap is relatively wide whereas for semiconductors it is narrow
  3. C
    The band-gap is narrow in width for both the insulators and conductors
  4. D
    The band-gap is equally wide for both conductors and semiconductors
Question 6Single Answer
Which of the following regions of operation are mainly responsible for heating of the transistor under switching operation?
1. Saturation region
2. Cut-off region
3. Transition from saturation to cut-off
4. Transition from cut-off to saturation
Select the correct answer using the codes given below
  1. A
    1, 2 and 4 only
  2. B
    1, 3 and 4 only
  3. C
    2 and 3 only
  4. D
    1 and 3 only
Question 7Single Answer
In a sinusoidal oscillator, sustained oscillations will be produced only if the loop gain (at the oscillation frequency) is
  1. A
    Less than unity but not zero
  2. B
    Zero
  3. C
    Unity
  4. D
    Greater than unity
Question 8Single Answer
The Class-B push-pull amplifier is an efficient two –transistor circuit, in which the two transistors operate in the following way:
  1. A
    Both transistors operate in the active region throughout the negative ac cycle
  2. B
    Both transistors operate in the active region for more than half-cycle but less than a whole cycle
  3. C
    One transistor conducts during the positive half-cycle and the other during the negative half-cycle
  4. D
    Full supply voltage appears across each of the transistors
Question 9Single Answer
PAC stands for______.
  1. A
    Permanent angle converter
  2. B
    Phase angle converter
  3. C
    Phase angle components
  4. D
    Phase angle capacitor
  5. E
    None of these
Question 10Single Answer
For normal operation of a transistor
  1. A
    Forward bias the emitter diode and reverse bias the collector diode
  2. B
    Forward bias the emitter diode as well as the collector diode
  3. C
    Reverse bias the emitter diode as well as the collector diode
  4. D
    Reverse bias the emitter diode and forward bias the collector diode
Question 11Single Answer
Consider the following statements:
The output of a linear circuit, driven with a sine wave at a frequency f, is itself a sine wave
1. at the same frequency
2. with chance of changed amplitude
3. with chances of changed amplitude and phase
Which of the above statements is/are correct? 
  1. A
    1 and 2
  2. B
    1 only
  3. C
    1 and 3
  4. D
    2 only 
Question 12Single Answer
Consider the following statements:
The main contribution to photo conduction is by
1. the generation of electron and hole pair by a photon
2. a donor electron jumping into the conduction band because of a photon’s energy
3. a valence electron jumping into an acceptor state because of a photon’s energy Which of the above statements is/are correct? 
  1. A
    1 only
  2. B
    2 only
  3. C
    3 only
  4. D
    1, 2 and 3
Question 13Single Answer
Thermal runaway is not possible in FET because as the temperature of the FET increase
  1. A
    mobility decreases
  2. B
     trans-conductance increases
  3. C
    drain current increases
  4. D
    trans-conductance decreases
Question 14Single Answer
For the same network, with 6 V DC connected at port A, 1 Ω connected at port B draws 7/3 A. if 8 V DC is connected to port A, the open circuit voltage at port B is
  1. A
    6 V
  2. B
    7 V
  3. C
    8 V
  4. D
    9 V
Question 15Single Answer
A signal may have frequency components which lie in the range of 0.001 Hz to 10 Hz. Which one of the following types of couplings should be chosen in a multistage amplifier designed to amplify the signal? 
  1. A
    Capacitor coupling
  2. B
    Direct coupling
  3. C
    Transformer coupling
  4. D
    Double-tuned transformer coupling
Question 16Single Answer
At temperature of 298 Kelvin, Silicon is not suitable for most-electronic applications, due to small amount of conductivity. This can be altered by
  1. A
    Gettering
  2. B
    Doping
  3. C
    Squeezing
  4. D
    Sintering
Question 17Single Answer
By doping Germanium with Gallium, the types of semi-conductors formed are
1. N type
2. P type
3. Intrinsic
4. Extrinsic
  1. A
    1 and 4
  2. B
    2 and 4
  3. C
    1 and 3
  4. D
    2 and 3
Question 18Single Answer
An n-type of silicon can be formed by adding impurity of:
1. Phosphorous
2. Arsenic
3. Boron
4. Aluminum 
Which of the above are correct ?
  1. A
    1 and 2
  2. B
    2 and 3
  3. C
    3 and 4
  4. D
    1 and 4
Question 19Single Answer
According to Einstein’s relationship for a semiconductor, the ratio of diffusion constant to the mobility of the charge carriers is
  1. A
    Variable and is twice the volt equivalent of the temperature
  2. B
    Constant and is equal to the volt equivalent of the temperature
  3. C
    Equal to two and is twice the volt equivalent of the temperature
  4. D
    Equal to one and is equal to the volt equivalent of the temperature
Question 20Single Answer
Swept-out voltage in PIN diode happens when PIN diode is
  1. A
    Forward biased and the thickness of the depletion layer decreases till I-region becomes free of mobile carriers
  2. B
    Reverse biased and the thickness of the depletion layer increases till I-region becomes free of mobile carriers
  3. C
    Forward biased and the thickness of the depletion layer increases till I-region becomes free of mobile carriers
  4. D
    Reverse biased and the thickness of the depletion layer decreases till I-region becomes free of mobile carriers
Question 21Single Answer
The number of holes in an N-type silicon with intrinsic value 1.5 × 1010/cm3 and doping concentration of 1017/cm3, by using mass-action law is
  1. A
    6.67 × 106/cc
  2. B
    4.44 × 10-25/cc
  3. C
    1.5× 10-24/cc
  4. D
    2.25 × 103/cc
Question 22Single Answer
A tunnel-diode is best suited for
  1. A
    Very low frequencies
  2. B
    50 Hz
  3. C
    100 Hz
  4. D
    Microwave frequencies
Question 23Single Answer
Small recovery time of a diode is most significant for
  1. A
    Line-frequency rectification
  2. B
    Switching operations
  3. C
    High-frequency rectifications and switching operations
  4. D
    Low-frequency rectifications and switching operations
Question 24Single Answer
In JFET, when operated above the pinch-off voltage, the
  1. A
    Depletion region becomes smaller
  2. B
    Drain current starts decreasing
  3. C
    Drain current remains practically constant
  4. D
    Drain current increases steeply
Question 25Single Answer
Thermal runaway is not possible in FET because, as the temperature of FET increases
  1. A
    The drain current increases
  2. B
    The mobility of charge carriers decreases
  3. C
    The mobility of charge carriers increases
  4. D
    The transconductance increases
Question 26Single Answer
Consider the following statements regarding an N-P-N Bipolar Junction Transistor:
1. Emitter diode is forward biased and collector diode is reverse biased
2. Emitter has many free electrons
3. Free electrons are injected into base and pass through collector
4. Depletion layers around junction J1 and J2 of BJT are widened 
    Which of the above statements are correct?
  1. A
    1, 2 and 4
  2. B
    1, 3 and 4
  3. C
    2, 3 and 4
  4. D
    1, 2 and 3
Question 27Single Answer
A freewheeling diode T phase controlled rectifier
  1. A
    Improves the line power factor
  2. B
    Enables inverse operation
  3. C
    Is responsible for additional reactive power
  4. D
    Is responsible for additional harmonics
Question 28Single Answer
The zeners incorporated within the encapsulations of some MOSFETs are meant for
  1. A
    Reducing the cost
  2. B
    Biasing the gate circuit
  3. C
    Self-protecting the device against transients
  4. D
    None of the above
Question 29Single Answer
When UJT is used for triggering an SCR, the wave-shape of the signal obtained from UJT circuit is
  1. A
    Sine wave
  2. B
    Saw tooth wave
  3. C
    Trapezoidal wave
  4. D
    Square wave
Question 30Single Answer
Darlington pairs are frequently used in linear ICs because, they
  1. A
    Do not require any capacitors or inductors
  2. B
    Have enormous impedance transformation capability
  3. C
    Can be readily formed/hooked from two adjacent transistors
  4. D
    Resemble emitter follower
Question 31Single Answer
In a MOS capacitance fabricate on a P-type semiconductor, strong inversion occurs, when potential is
  1. A
    Equal to Fermi level
  2. B
    Zero
  3. C
    Negative and equal to Fermi potential in magnitude
  4. D
    Positive and equal to Fermi potential in magnitude
Question 32Single Answer
A CMOS amplifier when compared to an N channel MOSFET has the advantage of
  1. A
    Higher cutoff frequency
  2. B
    Higher voltage gain
  3. C
    Higher current gain
  4. D
    Lower power dissipation
Question 33Single Answer
Consider the following statements regardingoptocouplers:
1. Optocouplers are LEDs driving photodiodes in a single package to provide electrical isolation between input and output
2. Optocouplers is LED driving a phototransistor in a single package that replaces pulse transformers working at input zero crossing
3. Optocouplers are used as temporary non fixed joints between optical fibre terminations 
  Which of the above statements are correct?
  1. A
    1, 2 and 3
  2. B
    1 and 2 only
  3. C
    1 and 3 only
  4. D
    2 and 3 only
Question 34Single Answer
Which of the following does not cause permanent damage to an SCR ?
  1. A
    High current
  2. B
    High rate of rise of current
  3. C
    High temperature rise
  4. D
    High rate of rise of voltage
Question 35Single Answer
The basic structure of an avalanche photodiode is
  1. A
    p+ – i – p – n+
  2. B
    p+ – I – n+
  3. C
    p+ – p- – n+
  4. D
    i – p- – n+
Question 36Single Answer
A five digits number is formed using the digits 1, 3, 5, 7 and 9 without repeating any of them. What is the sum of all such possible five digit numbers ?
  1. A
    6666660
  2. B
    6666600
  3. C
    6666666
  4. D
    6666606
Question 37Single Answer
Examples of an active display and a passive display respectively are
  1. A
    LCD and Gas discharge plasma
  2. B
    LED and LCD
  3. C
    Gas discharge plasma and LED
  4. D
    Electrophoretic Image display and LED
Question 38Single Answer
The dc resistivity and permeability exhibited by a type 1 superconductor are respectively
  1. A
    Zero and zero
  2. B
    Zero and unity
  3. C
    Unity and zero
  4. D
    Unity and unity
Question 39Single Answer
Statement (I):One of the mechanisms by which a transistor’s usefulness may be terminated, as the collector voltage is increased, is called punch through.
Statement (II): Punch through results from the increased width of the collector-junction transition region with increased collector-junction voltage
  1. A
    Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
  2. B
    Both Statement (I) and Statement (II) are individually true and Statement (II) is NOT the correct explanation of Statement (I)
  3. C
    Statement (I) is true but Statement (II) is false
  4. D
    Statement (I) is false but Statement (II) is true
Question 40Single Answer
Statement (I): Conduction takes place in an enhancement MOSFET only for gate voltages below the threshold level.
Statement (II):In an enhancement MOSFET, a channel of semiconductor of the same type as the source and drain is induced in the substrate by a positive voltage applied to the gate.
  1. A
    Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
  2. B
    Both Statement (I) and Statement (II) are individually true and Statement (II) is NOT the correct explanation of Statement (I)
  3. C
    Statement (I) is true but Statement (II) is false
  4. D
    Statement (I) is false but Statement (II) is true
Question 41Single Answer
Statement (I): MOSFET is a field effect transistor whose drain current is controlled by the voltage applied at the gate.
Statement (II): MOSFET is an insulated gate FET
  1. A
    Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
  2. B
    Both Statement (I) and Statement (II) are individually true and Statement (II) is NOT the correct explanation of Statement (I)
  3. C
    Statement (I) is true but Statement (II) is false
  4. D
    Statement (I) is false but Statement (II) is true
Question 42Single Answer
Statement (I): All passive components can be fabricated in a single chip.
Statement (II): As opposed to discrete circuits where all components are separately inserted and connected, in an integrated circuit, they are simultaneously created on a chip of semiconductor material during manufacturing
  1. A
    Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
  2. B
    Both Statement (I) and Statement (II) are individually true and Statement (II) is NOT the correct explanation of Statement (I)
  3. C
    Statement (I) is true but Statement (II) is false
  4. D
    Statement (I) is false but Statement (II) is true
Question 43Single Answer
What is an advantage of MOS transistor structure in integrated circuits?
  1. A
    Faster switching
  2. B
    Less capacitance
  3. C
    Higher component density and lower cost
  4. D
    Lower resistance
Question 44Single Answer
An LTI system has a wide-sense stationary (WSS) input signal with zero mean. Its output is
  1. A
    Non-zero mean and non-WSS signal
  2. B
    Zero mean and WSS signal
  3. C
    Non-zero mean and WSS signal
  4. D
    Zero mean and non-WSS signal
Question 45Single Answer
In degenerately doped n conduction n-type semiconductor, the Fermi level lies in conduction band when
  1. A
    Concentration of electrons in the conduction band exceeds the density of states in the valence band
  2. B
    Concentration of electrons in the valence band exceeds the density of states in the conduction band
  3. C
    Concentration of electrons in the conduction band exceeds the product of the density of states in the valence band and conduction band
  4. D
    None of the above
Question 46Single Answer
In intrinsic semiconductors, the Fermi level lies?
  1. A
    At mid-gap
  2. B
    Near valence band
  3. C
    Near conduction band
  4. D
    Outside the band gap
Question 47Single Answer
Which material is a direct band-gap semiconductor?
  1. A
    Gallium Arsenide
  2. B
    Germanium
  3. C
    Silicon
  4. D
    Tin
Question 48Single Answer
Indirect band-gap semiconductors require phonon interaction because?
  1. A
    Charge neutrality
  2. B
    Energy conservation
  3. C
    Momentum conservation
  4. D
    Thermal equilibrium
Question 49Single Answer
Band gap of silicon at room temperature is approximately?
  1. A
    0.66 eV
  2. B
    0.72 eV
  3. C
    1.43 eV
  4. D
    1.12 eV
Question 50Single Answer
Increase in temperature causes band gap of semiconductor to?
  1. A
    Increase
  2. B
    Decrease
  3. C
    Remain constant
  4. D
    Become zero
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