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Latest BTSC Laboratory Assistant Electrical Exam Question (Objective Questions), MCQ in English

Subjects : Technical Subject (Electrical)

Question Bank BTSC Laboratory Assistant (Electrical) Exam - English
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Technical Subject (Electrical)

Question 1Single Answer
When a very small amount of higher conducting metal is added to a conductor, its conductivity will 
  1. A
    increase
  2. B
     decrease
  3. C
    remain the same 
  4. D
    increase or decrease depending on the impurity
Question 2Single Answer
An electrically balanced atom has 30 protons in its nucleus and 2 electrons in its outermost shell. The materials made of such atom is
  1. A
    a conductor
  2. B
    an insulator
  3. C
    a semiconductor 
  4. D
    a superconductor
Question 3Single Answer
The temperature coefficient of resistance of a doped semiconductor is
  1. A
    always positive
  2. B
    always negative
  3. C
    zero 
  4. D
    positive or negative depending upon the level of doping 
Question 4Single Answer
In the slice processing of an integrated circuit
  1. A
    components are formed in the areas where silicon dioxide remains
  2. B
    components are formed in the areas where silicon dioxide has been removed
  3. C
    the diffusing elements diffuse through silicon dioxide 
  4. D
    only on diffusion process is used 
Question 5Single Answer
Permanent magnet loses the magnetic behaviour when heated because of
1. atomic vibration
2. dipole vibration
3. realignment of dipoles
Which of the above are correct?
  1. A
    1  and 2 only 
  2. B
    1 and 3 only
  3. C
    1, 2 and 3         
  4. D
    2 and 3
Question 6Single Answer
A Zener regulator has an input voltage varying between 20 V and 30 V. The desired regulated voltage is 12 V, while the load varies between 140  and 10k  The maximum resistance in series with the unregulated source and Zener diode would be
  1. A
    3.3
  2. B
    6.6
  3. C
    36.6
  4. D
    93.3
Question 7Single Answer
A short in any type of circuit (series, parallel or combination) causes the total circuit
1. resistance to decrease
2. power to decreases
3. current to increase
Which of the above are correct?
  1. A
    2  and 3 
  2. B
    2 and 4
  3. C
    1 and 4 
  4. D
    1 and 3 
Question 8Single Answer
An air-cored solenoid of 250 turns has a cross-sectional area A = 80 cm2 and length l = 100 cm. The value of its inductance is
  1. A
    0.425 mH          
  2. B
    0.628 mH
  3. C
    0.751 mH 
  4. D
    0.904 mH
Question 9Single Answer
The current in a coil changes uniformly from 10 A to 1 A in half a second. A voltmeter connected across the coil gives a reading of 36 V. The self-inductance of the coil is
  1. A
    0.5 H 
  2. B
    1 H
  3. C
    2 H       
  4. D
    4 H 
Question 10Single Answer
In a mutually coupled circuit, the primary current is reduced from 4A to zero in 10 s.  A voltage of 40000 V is observed across the secondary. The mutual inductance between the coils is
  1. A
    100 H 
  2. B
    10 H
  3. C
    0.1 H 
  4. D
    0.01 H 
Question 11Single Answer
A semiconductor differs from a conductor in that it has
  1. A
    Only one path for the free electrons in the valence band
  2. B
    Only one path for holes in the conduction band
  3. C
    Two paths followed by free electrons and holes, one an ordinary path in the conduction band and the other one an extraordinary path in the valence band, respectively 
  4. D
    Two paths followed by free electrons and holes, one an extraordinary path in the conduction band and the other one an ordinary path in valence band, respectively 
Question 12Single Answer
Which of the following circuits is used for converting a sine wave into a square wave?
  1. A
    Monostablemultivibrator
  2. B
    Bistablemultivibrator
  3. C
    Schmitt trigger circuit 
  4. D
    Darlington complementary pair
Question 13Single Answer
Which of the following elements of electrical engineering cannot be analyzed using Ohm’s law ?
  1. A
    Capacitors
  2. B
    Inductors
  3. C
    Transistors
  4. D
    Resistance
Question 14Single Answer
Consider the following statements: A power supply uses bridge rectifier with a capacitor input filter. If one of the diodes is defective, then
1. The dc load voltage will be lower than its expected value
2. Ripple frequency will be lower than its expected value
3. The surge current will increase considerably
Which of the above statements are correct?
  1. A
    1  and 2 only 
  2. B
    1 and 3 only
  3. C
    2 and 3 only 
  4. D
    1, 2 and 3 
Question 15Single Answer
Three identical amplifiers each having a voltage gain of 50 are cascaded. The open loop voltage gain of the combined amplifier is
  1. A
    71 dB 
  2. B
    82 dB 
  3. C
    91 dB 
  4. D
    102 dB 
Question 16Single Answer
A clamper circuit
1. Adds or subtracts a dc voltage to or from a waveform
2. Does not change the shape of the waveform
Which of the above statements are correct? 
  1. A
    1 only 
  2. B
    2 only 
  3. C
    Both 1 and 2 
  4. D
    Neither 1 nor 2 
Question 17Single Answer
If a carrier of 100% modulated AM is suppressed before transmission, the power saving is nearly
  1. A
    50% 
  2. B
    67%
  3. C
    100% 
  4. D
    125%
Question 18Single Answer
When the modulating frequency is doubled the modulation index is halved and the modulating voltage remains constant. This happens when the modulating system is
  1. A
    AM 
  2. B
    PM
  3. C
    FM       
  4. D
    Delta Modulation
Question 19Single Answer
The four basic elements in a PLL are loop filter, loop amplifier, VCO and
  1. A
    Up converter
  2. B
    Down converter
  3. C
    Phase detector
  4. D
    Frequency multiplier
Question 20Single Answer
In a frequency modulated (FM) system, when the audio frequency is 500 Hz and audio frequency voltage is 2.4 V, the frequency deviation is 4.8 kHz. If the audio frequency voltage is now increased to 7.2 V then what is the new value of deviation?
  1. A
    0.6 kHz 
  2. B
    3.6 kHz
  3. C
    12.4 kHz 
  4. D
    14.4 kHz
Question 21Single Answer
If a square matrix of order 100 has exactly 15 distinct eigenvalues, then the degree of the minimum polynomial is 
  1. A
    At least 15 
  2. B
    At most 15 
  3. C
    Always 15 
  4. D
    Exactly 100
Question 22Single Answer
For high speed reading and storing of information in a computer, the core shall be of 
  1. A
    Ferrite 
  2. B
    Piezoelectric 
  3. C
    Pyroelectric 
  4. D
    Ferromagnetic above 768°C
Question 23Single Answer
Soft magnetic materials should have 
  1. A
    Large saturation magnetization and large permeability 
  2. B
    Low saturation magnetization and large permeability 
  3. C
    Large saturation magnetization and low permeability 
  4. D
    Low saturation magnetization and low permeability 
Question 24Single Answer
Orbital magnetic moment of an electron, in an atom, is of the order of 
  1. A
    0.1 Bohr magneton 
  2. B
    1.0 Bohr magneton 
  3. C
    10 Bohr magneton 
  4. D
    100 Bohr magneton
Question 25Single Answer
When the temperature of a ferromagnetic material exceeds the Curie temperature, it behaves similar to a 
  1. A
    Diamagnetic material 
  2. B
    Ferrimagnetic material 
  3. C
    Paramagnetic material 
  4. D
     Antiferromagnetic material
Question 26Single Answer
What is the correct sequence of the following materials in ascending order of their resistivity ?
1. Iron
2. Silver
3. Constantan
4. Mica
5. Aluminium
Select the correct answer using the codes given below : 
  1. A
    2, 5, 1, 3 and 4 
  2. B
    4, 5, 3, 1 and 2 
  3. C
    2, 3, 1, 5 and 4 
  4. D
    4, 5, 1, 3 and 2
Question 27Single Answer
In the first Cauer network, with a pole at infinity, the first element must be
  1. A
    Series capacitor 
  2. B
    Series inductor 
  3. C
    Shunt capacitor 
  4. D
    Shunt inductor
Question 28Single Answer
The total magnetic moment
1. is called saturation magnetization.
2. depends on the number of magnetic dipoles per unit volume, the instant electric current and the area of the current loop.
Which of the above statements is/are correct ? 
  1. A
    1 only 
  2. B
    2 only 
  3. C
    Both 1 and 2 
  4. D
    Neither 1 nor 2
Question 29Single Answer
Susceptibility of a diamagnetic material is 1. Negative
2. Positive
3. Dependent on the temperature
4. Independent of the temperature 
  1. A
    1 and 2 only 
  2. B
    1 and 3 only 
  3. C
    2 and 3 only      
  4. D
    1, 2 and 3
Question 30Single Answer
Superconductivity is a material property associated with 
  1. A
    Changing shape by stretching 
  2. B
    Stretching without breaking 
  3. C
    A loss of thermal resistance 
  4. D
    A loss of electrical resistance
Question 31Single Answer
Assuming both the voltage sources are in phase, the value of R for which maximum power is transferred from circuit A to circuit B is
  1. A
    0.8 Ω
  2. B
    1.4 Ω
  3. C
    2 Ω
  4. D
    2.8 Ω
Question 32Single Answer
For the intrinsic gallium-arsenide, the conductivity at room temperature 25°C is 10-6 (ohm-m)-1, the electron and hole nobilities are 0.85 m2/V-s and 0.04 m2/V-s respectively. What is the intrinsic carrier concentration at the room temperature?
  1. A
    7.0 × 1012 m-3
  2. B
    7.0 × 10-12 m-3
  3. C
    7.0 × 10-12 m3
  4. D
    7.0 × 1012 m3
Question 33Single Answer
The resistivity of intrinsic germanium at 30°C is 0.46 –m. What is the intrinsic carrier density at 30°C if the electron mobility is 0.38 m2/V-s and the hole mobility is 0.18 m2/V-s?
  1. A
    9.2 × 105/m3
  2. B
    2.77 × 103/m3
  3. C
    2.43 × 1019/m3
  4. D
    8.9 × 1012/m3
Question 34Single Answer
Heat conduction in a semiconductor takes place
  1. A
    By the mobility of the carriers
  2. B
    Due to energy gap between conduction band and valency band
  3. C
    By the holes and thermal vibrations of atoms
  4. D
    By the electrons and thermal vibrations of atoms
Question 35Single Answer
Brewster angle is the angle when a wave is incident on the surface of a perfect dielectric at which there is no reflected wave and the incident wave is
  1. A
    Parallel polarized
  2. B
    Perpendicularly polarized
  3. C
    Normally polarized
  4. D
    None of the above
Question 36Single Answer
An electrical breakdown of a p-n junction occurs if
  1. A
    Forward voltage increases up to the rating
  2. B
    Reverse voltage increases beyond the rating
  3. C
    Forward voltage decreases below the rating
  4. D
    Reverse voltage decreases below the rating
Question 37Single Answer
The chief deterrent to the widespread application of superconducting materials is
  1. A
    Very difficult to form, machine or case
  2. B
    The difficult in attaining and maintaining extremely low temperature
  3. C
    The poor strength-to-weight ratio
  4. D
    The lower oxidation rate at elevated temperatures
Question 38Single Answer
Which one of the following properties is not observed in the carbon nanotubes ?
  1. A
    High stiffness and strengths
  2. B
    Low densities
  3. C
    Unusual electrical property
  4. D
    Non-ductile
Question 39Single Answer
The evidence for the importance of electron-phonon interaction in super-conductors comes from
  1. A
    Meissner effect
  2. B
    Josephson effect
  3. C
    Isotope effect
  4. D
    x quantization experiments
Question 40Single Answer
Which one of the following materials is used for cable insulation ?
  1. A
    Phenol formaldehyde
  2. B
    Polytetrafluoroethylene
  3. C
    Polyvinyl chloride
  4. D
    Acrylonitrile butadiene styrene
Question 41Single Answer
Resistance switching is normally resorted in case of
  1. A
    Air blast CB
  2. B
    Bulk oil CB
  3. C
    Minimum oil CB
  4. D
    All types of CB
Question 42Single Answer
By transmitting power at high voltage
  1. A
    it will give poor voltage regulation
  2. B
    it will give better voltage regulation
  3. C
    it will not effect voltage regulation
  4. D
    None of these
Question 43Single Answer
Which statement about the daily load curve is valid ?
  1. A
    The area under the curve gives the average demand
  2. B
    The ratio of the area under the curves to the total area of rectangle in which it is contained gives the load factor for the day
  3. C
    The peak of the curve gives the installed capacity of the plant
  4. D
    The area of the curves divided by the number of hours gives load factor
Question 44Single Answer
High voltage Schring bridge is used to measure
  1. A
    large capacitance without additional element
  2. B
    small capacitance without additional element
  3. C
    medium value capacitance
  4. D
    None of these
Question 45Single Answer
Draw - in - system of laying underground cables has the drawback (s) of
  1. A
    higher cost
  2. B
    reduced current carrying capacity of the cables
  3. C
    requirements of much deeper and wider trenches
  4. D
    repairs, alterations or additions difficult
  5. E
    all of the above except
Question 46Single Answer
Surge impedance of a transmission line is
  1. A
    independent of its length
  2. B
    dependent on its length
  3. C
    independent on its temperature
  4. D
    none of the above
Question 47Single Answer
If two synchronous generators connected in parallel loose synchronism, it will lead to
  1. A
    stalling of generators
  2. B
    wild fluctuations in current
  3. C
    wild fluctuations in current and voltage
  4. D
    None of these
Question 48Single Answer
A differential relay responds to
  1. A
    algebraic difference of two or more similar electrical quantities
  2. B
    vector difference of two or more similar electrical quantities
  3. C
    algebraic difference between two currents
  4. D
    algebraic difference between two voltages
Question 49Single Answer
The conductor carries more current on the surface in comparison to its core. This phenomenon is called the
  1. A
    Skin effect
  2. B
    Corona
  3. C
    Ferranti effect
  4. D
    Lenz's effect
Question 50Single Answer
A booster is connected in
  1. A
    series with the feeder
  2. B
    parallel with the feeder
  3. C
    both (a) and (b) are correct
  4. D
    none of these
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