[FINAL ANSWER KEY]Electronic Mechanic Exam Answer Key

Electronic Mechanic Exam Answer Key: Question Paper Code: 81/2023/OL,Category Code: 333/2019,Exam: Junior Instructor (Electronic Mechanic),Date of Test 13-06-2023,Department: Industrial Training.

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Electronic Mechanic Exam Answer Key

Question1:-Two resistors of the same value are connected in parallel and a 100V
supply is connected across the terminals. If the total current taken is 10A, what is
the value of each resistor?
A:-5Ω
B:-10Ω
C:-20Ω
D:-40Ω
Correct Answer:- Option-C

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Question2:-Select the colour code for a resistor of value 680kΩ with ±5% tolerance
from the given options.
A:-Green, Blue, Orange and Silver
B:-Green, White, Yellow and Gold
C:-Blue, Violet, Orange and Silver
D:-Blue, Grey, Yellow and Gold
Correct Answer:- Option-D

Question3:-The reactance of a capacitor with increase in frequency of the
current flowing through it.
A:-increases
B:-decreases
C:-remains the same
D:-None of the above
Correct Answer:- Option-B

Question4:-The quality factor ‘Q’ of a coil at resonance is 100. If the resistance of
the coil is 10Ω, what is the value of it’s reactance at resonance?
A:-10Ω
B:-1kΩ
C:-10kΩ
D:-1000kΩ
Correct Answer:- Option-B

Question5:-Two capacitors 100μF each, connected in parallel are then connected in
series with a third capacitor of value 200μF. What is the effective capacitance of the
entire combination?
A:-400μF
B:-250μF
C:-100μF
D:-300μF
Correct Answer:- Option-C

Question6:-Which of the following devices exhibits negative resistance?
A:-Zener diode
B:-Varactor diode
C:-Light emitting diode
D:-Tunnel diode
Correct Answer:- Option-D

Question7:-Which breakdown mechanism is likely to take place in a heavily doped
PN junction diode?
A:-Avalanche breakdown
B:-Zener breakdown
C:-Both avalanche and zener breakdowns
D:-Neither avalanche nor zener breakdowns
Correct Answer:- Option-B

Question8:-Which of the following statements are not correct for a JFET?
(i) It is a bipolar device
(ii) It has high input impedance
(iii) It is a current controlled device
(iv) Small in size compared to BJT
A:-(i) and (ii)
B:-(ii) and (iv)
C:-(iii) and (iv)
D:-(i) and (iii)
Correct Answer:- Option-D

Question9:-The arrow pointer on a transistor symbol indicates
A:-direction of minority carrier current
B:-direction of majority carrier current
C:-direction of hole current
D:-direction of electron current
Correct Answer:- Option-C

Question10:-For the operation of n-channel E-MOSFET, the gate voltage must be
A:-low positive
B:-low negative
C:-high positive
D:-high negative
Correct Answer:- Option-C

Question11:-Which of the following is an adjustable voltage regulator IC?
A:-LM7805
B:-LM317
C:-LM320
D:-LM340
Correct Answer:- Option-B

Question12:-The forbidden energy gap of Silicon at room temperature is
A:-1.12 eV
B:-5 eV
C:-0.72 eV
D:-0.5 eV
Correct Answer:- Option-A

Question13:-A heavily doped p-type semiconductor material is
A:-positively charged
B:-negatively charged
C:-electrically neutral
D:-None of the above
Correct Answer:- Option-C

Question14:-At a PN-junction, electrons diffuse from the N-region to the P-region
because of the
A:-difference in carrier concentration
B:-attraction of holes in the P-region
C:-potential difference at the junction
D:-None of the above
Correct Answer:- Option-A

Question15:-Which of the following statements about the leakage current in a
semiconductor diode are correct?
(i) Created due to the flow of majority carriers.
(ii) Remains the same irrespective of the changes in biasing voltage.
(iii) Varies with variation in temperature.
(iv) Of the order of microamperes in silicon and nanoamperes in germanium
A:-(i) and (iv)
B:-(iii) and (iv)
C:-(ii) and (iii)
D:-(i) and (iii)
Correct Answer:- Option-C

Question16:-Which of the following defines base transportation factor of an NPN
transistor?
A:-The ratio of the number of electrons arriving at collector to the number of
emitted electrons
B:-The ratio of the electron current to the total emitter current
C:-Ratio of the collector current to the emitter current
D:-Ratio of collector current to base current
Correct Answer:- Option-A

Question17:-Which transistor configuration has very high input resistance and very
low output resistance?
A:-Common Base
B:-Common Emitter
C:-Common Collector
D:-Both CB and CE
Correct Answer:- Option-C

Question18:-The current gain α of a transistor is 0.99. What is the value of its β?
A:-0.5
B:-99
C:-9.9
D:-198
Correct Answer:- Option-B

Question19:-In a BJT amplifier, the Q-point is stabilized by
A:-Keeping the temperature constant
B:-Keeping the base current constant
C:-Changing the base current to keep and constant
D:-Changing the emitter current to keep and constant
Correct Answer:- Option-C

Question20:-Factors that affect the lower cut-off frequency of a RC coupled CE
amplifier are
(i) Ineffective bypassing of emitter bypass capacitors
(ii) Bypassing effect of junction capacitances
(iii) Signal loss across coupling capacitors
(iv) Loading effect of subsequent stages
A:-(i) and (ii)
B:-(ii) and (iii)
C:-(ii) and (iv)
D:-(i) and (iii)
Correct Answer:- Option-D

Question21:-Which coupling scheme is preferred for a multistage amplifier used to
amplify signals below 10 Hz?
A:-Direct coupling
B:-Transformer coupling
C:-RC coupling
D:-All of the above
Correct Answer:- Option-A

Question22:-Which of the following oscillator circuits is suitable to generate audio
frequency signals?
A:-Hartley oscillator
B:-Crystal oscillator
C:-Colpitts oscillator
D:-Wien bridge oscillator
Correct Answer:- Option-D

Question23:-Which of the following circuit can be used as a memory element?
A:-Monostable Multivibrator
B:-Bistable Multivibrator
C:-Astable Multivibrator
D:-All of the above
Correct Answer:- Option-B

Question24:-The differential mode gain of an op-amp is . If the common mode
gain is 0.1, what is its CMRR?
A:- 10^-6
B:- 10⁴
C:- 10⁵
D:-10⁶
Correct Answer:- Option-D

Question25:-Which of the following is not the characteristic of an ideal op-amp?
A:-Infinite input resistance
B:-Infinite output resistance
C:-Infinite voltage gain
D:-Infinite bandwidth
Correct Answer:- Option-B
Question26:-The electrolyte used in dry cell?
A:-Ammonium chloride
B:-Nitric acid
C:-Manganese dioxide
D:-Sulphuric acid
Correct Answer:-Question Cancelled

Question27:-The specific gravity of the electrolyte in a lead acid battery can be
measured using .
A:-Ammeter
B:-Barometer
C:-Hydrometer
D:-Voltmeter
Correct Answer:- Option-C

Question28:-Conventionally the energy stored in a battery is measured in
_.
A:-Ampere – Volt
B:-Ampere – Hour
C:-Ampere/Hour
D:-Ampere/Volt
Correct Answer:- Option-B

Question29:-In a full wave rectifier if the input signal frequency is 50 Hz, find the
output signal frequency?
A:-25 Hz
B:-50 Hz
C:-100 Hz
D:-150 Hz
Correct Answer:- Option-C

Question30:-Based on the input cycles utilized, the rectifiers can be classified as
_.
A:-Full wave rectifier
B:-Half wave rectifier
C:-Positive rectifier
D:-Both (1) and (2)
Correct Answer:- Option-D

Question31:-The following symbol represents in an electrical system.
A:-Rectifier
B:-Inverter
C:-Chopper
D:-UPS
Correct Answer:-Question Cancelled

Question32:-Choose the disadvantage of SMPS:
A:-Low efficiency
B:-Noise exist due to high frequency switching
C:-High power dissipation
D:-None of the above
Correct Answer:- Option-B

Question33:-The regulated DC power supply consists of .
A:-Rectifier
B:-Filter
C:-Voltage regulator
D:-All the above
Correct Answer:- Option-D

Question34:-The instruments used for critical load during temporary power failure
occur is .
A:-UPS
B:-SMPS
C:-MPS
D:-RCCP
Correct Answer:- Option-A

Question35:-What is used to neutralize a spilled electrolyte from a lead acid
battery?
A:-Boric acid
B:-Water
C:-Sulphuric acid
D:-Baking soda
Correct Answer:- Option-D

Question36:-The self inductance of two coils is 16 mH and 4 mH respectively. If the
coefficient of coupling is 0.7, the mutual inductance between the coils is,
A:-8 mH
B:-5.6 mH
C:-4.2 mH
D:-4 mH
Correct Answer:- Option-B

Question37:-The voltage and current in ac circuit is represented by v =
Sin(ωt+30°) and i = Sin(ωt–45°).
The power factor angle of the circuit is
A:-15°
B:-45°
C:-30°
D:-75°
Correct Answer:- Option-D

Question38:-What is the true condition for maximum power transform from source
to load as per maximum power transform theorem?
A:-Source resistance is equal to load resistance
B:-Source resistance is negligible
C:-Load resistance if negligible
D:-Load resistance is infinity
Correct Answer:- Option-A

Question39:-Power factor of a parallel resonant circuit is
A:-Zero
B:-Infinity
C:-Unity
D:-–1
Correct Answer:- Option-C

Question40:-Which of the following instruments measure RMS value of unknown
current?
A:-PMMC
B:-Electrodynamic only
C:-Moving iron only
D:-Both (2) and (3)
Correct Answer:- Option-D

Question41:-The energy meter installed near the main switch in residences and
other locations is,
A:-An indicating on deflecting type
B:-An absolute instrument
C:-Recording type instrument
D:-An integrating type instrument
Correct Answer:- Option-D

Question42:-The extension range of an ammeter and voltmeter can be made
represented by,
A:-Using a multiplier and shunt
B:-Using shunt and multiplier
C:-Using series capacitor and series inductor
D:-Using series inductor and series capacitor
Correct Answer:- Option-B

Question43:-In a moving iron instrument which is spring controlled, a current of 5A
produces a deflection of 60°. What will be the deflection when a current of 2A is
flowing through the coil of the instrument?
A:-9.6°
B:-4°
C:-14°
D:-10°
Correct Answer:- Option-A

Question44:-According to Faraday’s law of electromagnetic induction,
A:-Magnetic field is produced by time varying electric flux
B:-Magnetic field is associated with a moving charge
C:-Electric field is produced by time varying magnetic flux
D:-Electric field is produced by magnetic flux linked
Correct Answer:- Option-C

Question45:-Which of the following is not the unit of energy?
A:-kWh
B:-Joules/second
C:-Watt hour
D:-Joules
Correct Answer:- Option-B

Question46:-The rise time ‘t’ of a signal applied to CRO and bandwidth ‘B’ of the
CRO are related as
A:-t × B = 0.35
B:-t × B = 1
C:-t/B = 0.35
D:-t/B = 1
Correct Answer:- Option-A

Question47:-An oscilloscope is used to measure the phase difference or the
frequency relationship between two unknown signals, it is used in the
A:-CHOP mode
B:-ALT mode
C:-Trigger mode
D:-X-Y mode
Correct Answer:- Option-D
Question48:-A triangular wave shape is obtained in a function generator
A:-by differentiating a square wave
B:-by integrating a square wave
C:-by integrating a sine wave
D:-by differentiating a sine wave
Correct Answer:- Option-B
Question49:-In a digital multimeter resistance is measured by using
A:-Variable current source
B:-Variable voltage source
C:-Constant current source
D:-Constant voltage source
Correct Answer:- Option-C
Question50:-The delay line in CRO is placed after
A:-Horizontal Amplifier
B:-Vertical amplifier
C:-Trigger circuit
D:-Power supply
Correct Answer:- Option-B

Question51:-The recommended configuration for soldering is
A:-Wave joint
B:-Butt joint
C:-Lap joint
D:-Scarf joint
Correct Answer:- Option-C

Question52:-Addition of increases the mechanical property of a tin-lead
solder.
A:-Antimony
B:-Bismuth
C:-Molybdenum
D:-Cerium
Correct Answer:- Option-A

Question53:-The purpose of using flux in soldering is
A:-Increase the fluidity of solder metal
B:-Fed up gaps in a bad joint carbon steel
C:-Prevents oxides forming
D:-Wash any surplus solder
Correct Answer:- Option-C

Question54:-Heat for soldering process is supplied by
A:-Soldering iron
B:-Induction furnace
C:-Electric resistance method
D:-Any of the above
Correct Answer:- Option-A

Question55:-Temperature range in soldering process is
A:-40°C – 100°C
B:-180°C – 250°C
C:-600°C – 900°C
D:-1000°C – 2000°C
Correct Answer:- Option-B

Question56:-Tropospheric scatter is used with frequency in the following range
A:-UHF
B:-VHF
C:-HF
D:-VLF
Correct Answer:- Option-A

Question57:-The maximum power of single side band waves under distortionless
condition is
A:-1.5 Pc
B:-Pc/2
C:-Pc/4
D:-Pc/3
Correct Answer:- Option-C
Question58:-Wide band FM is the case where the modulation index is
A:-around unity
B:-much greater than unity
C:-much less than unity
D:-around zero
Correct Answer:- Option-B
Question59:-In a super heterodyne receiver the frequency of local oscillator is
A:-half that of incoming signal
B:-slightly less than that of incoming signal
C:-higher than that of incoming signal
D:-equal to that of incoming signal
Correct Answer:- Option-C

Question60:-In a line of sight system the receiving and transmitting antenna
heights are 10m and 100m respectively above the surface of the earth. The range
of the system will be approximately
A:-32 km
B:-82 km
C:-25 km
D:-52 km
Correct Answer:- Option-D

Question61:-QPSK system uses a phase shift of
A:-π/2
B:-π/4
C:-2π
D:-3π
Correct Answer:- Option-A

Question62:-FDM uses __ to prevent modulated signal from overlapping.
A:-Guard band
B:-Physical hardware device
C:-Carrier frequencies
D:-De-Multiplexers
Correct Answer:- Option-A

Question63:-A 500W carrier is amplitude modulated to a depth of 60%. What is the
total power of the transmitted wave.
A:-250W
B:-520W
C:-950W
D:-590W
Correct Answer:- Option-D

Question64:-Which fiber is preferred for long distance communication
A:-Graded index
B:-Step index single mode
C:-Step index multimode
D:-Graded index multimode
Correct Answer:- Option-B

Question65:-Optical Time Domain Reflectometer is used to measure
A:-Wavelength
B:-Eye pattern
C:-Losses in optical fibre communication
D:-Time of reflection
Correct Answer:- Option-C

Question66:-Which of the following is the feature of mobile communication?
A:-High load balancing capacity
B:-Highly scalable
C:-Good network management system
D:-All of the above
Correct Answer:- Option-D

Question67:-The process of converting the analog sample into discrete form is
called
A:-Sampling
B:-Quantization
C:-Multiplexing
D:-Modulation
Correct Answer:- Option-B

Question68:-If physical quantities like force, tension, or pressure are to be
measured, then LVDT acts as a
A:-Primary transducer
B:-Secondary transducer
C:-Both are correct
D:-Both are wrong
Correct Answer:- Option-B

Question69:-Identify the incorrect statement

LVDT gives high output value so that there is no need for any amplifier circuit
for the amplification process

LVDT is not sensitive to stray magnetic field
A:-Only statement 1
B:-Only statement 2
C:-Both statements 1 and 2
D:-None of the statements
Correct Answer:- Option-B

Question70:-Which metal will have a large range of detection by inductive proximity
sensor?
A:-Aluminium
B:-Copper
C:-Iron
D:-Lead
Correct Answer:- Option-C

Question71:-In semiconductor strain guage, when a tensile strain is applied,
A:-Resistance increases in n-type material
B:-Resistance increases in p-type material
C:-Resistance increases in both p and n type material
D:-Resistance decreases in both p and n type material
Correct Answer:- Option-B

Question72:-Thermocouple works on
A:-Seebeck effect
B:-Thomson effect
C:-Kelvin effect
D:-Peltier effect
Correct Answer:- Option-A

Question73:-The temperature of steam at around 540°C can be measured by
A:-Thermometer
B:-Thermopile
C:-Thermocouple
D:-Radiation pyrometer
Correct Answer:- Option-D

Question74:-In a thermistor, change in resistance is measured using a
A:-Wheatstone bridge
B:-Anderson’s bridge
C:-Hay’s bridge
D:-Maxwell’s bridge
Correct Answer:- Option-A

Question75:-Capacitive transducers can be used for the measurement of liquid
level. The principle of operation used to this case is
A:-Change of capacitance with change of distance between plates
B:-Change of dielectric strength
C:-Change of area of plates
D:-None of the above
Correct Answer:- Option-B

Question76:-Inductive transducers are mainly used for the measurement of
A:-Temperature
B:-Velocity
C:-Force
D:-Displacement
Correct Answer:- Option-D

Question77:-Which device provides electrical isolation between input circuit and
output circuit?
A:-Optical sensor
B:-Photo diode
C:-Photo transistor
D:-Opto coupler
Correct Answer:- Option-D

Question78:-An OR gate is equivalent to two switches connected in _.
A:-Series
B:-Parallel
C:-Inverted
D:-Directly
Correct Answer:- Option-B

Question79:-The carry output of a two-input half-adder can be realised by using a
logic gate.
A:-NOT
B:-OR
C:-AND
D:-XOR
Correct Answer:- Option-C

Question80:-The Gray code equivalent of a 4-bit binary number 1010 is .
A:-1011
B:-1111
C:-1001
D:-10101
Correct Answer:- Option-B

Question81:-The XNOR gate gives a high output when inputs are .
A:-1 and 0
B:-0 and 1
C:-equal
D:-inverted
Correct Answer:- Option-C

Question82:-Ripple counters are counters
A:-Synchronous
B:-Asynchronous
C:-Random
D:-Johnson
Correct Answer:- Option-B

Question83:-Decade counter counts up to states.
A:-2
B:-100
C:-10
D:-1000
Correct Answer:- Option-C

Question84:-According to De Morgan’s theorem NAND gate is equivalent to
gate.
A:-OR
B:-AND
C:-Bubbled OR
D:-Bubbled AND
Correct Answer:- Option-C

Question85:-The number of select lines required to design an 8×1 multiplexer.
A:-2
B:-3
C:-4
D:-8
Correct Answer:- Option-B

Question86:-A flip flop can one bit of information.
A:-Store
B:-Complement
C:-Add
D:-Subtract
Correct Answer:- Option-A

Question87:-A shift register can convert serial to parallel data.
A:-SISO
B:-SIPO
C:-PISO
D:-PIPO
Correct Answer:- Option-B

Question88:-Which one is an Analog to Digital converter?
A:-Counter type
B:-Flash type
C:-R-2R ladder type
D:-Dual Slope
Correct Answer:-Question Cancelled

Question89:-A decade counter requires .
A:-4 flip flops
B:-2 flip flops
C:-8 flip flops
D:-16 flip flops
Correct Answer:- Option-A

Question90:-Three T flip flops are connected to form a counter, how many counting
sequences it can count.
A:-2
B:-4
C:-7
D:-8
Correct Answer:- Option-D

Question91:-8086 Microprocessor is a bit processor.
A:-8
B:-16
C:-32
D:-20
Correct Answer:- Option-B

Question92:-8086 Microprocessor flag register has flags.
A:-8
B:-9
C:-10
D:-16
Correct Answer:- Option-B

Question93:- flag is used for debugging in 8086.
A:-OF
B:-DF
C:-IF
D:-TF
Correct Answer:- Option-D

Question94:-8086 can access upto memory locations.
A:-1 MB
B:-64 KB
C:-32 MB
D:-4 KB
Correct Answer:- Option-A

Question95:-MOV AX, [BX] is an example of a mode of addressing.
A:-Register Addressing
B:-Direct Addressing
C:-Register Indirect Addressing
D:-Based Addressing
Correct Answer:- Option-C

Question96:-8051 is a bit Microcontroller.
A:-8 bit
B:-16 bit
C:-24 bit
D:-32 bit
Correct Answer:- Option-A
Question97:-Pin number 40 of the 8051 microcontrollers is .
A:-Ground
B:-VCC
C:-Reset
D:-Address Latch Enable
Correct Answer:- Option-B

Question98:-Microcontrollers have no flag.
A:-Carry
B:-Overflow
C:-Parity
D:-Zero
Correct Answer:- Option-D

Question99:-The Serial data communication in 8051 is controlled by
registers.
A:-SCON
B:-TCON
C:-SMOD
D:-TMOD
Correct Answer:- Option-A

Question100:-8051 Microcontroller have _ interrupt signals.
A:-8
B:-7
C:-6
D:-5
Correct Answer:- Option-D