UPRVUNL JE Electrical 21-Oct-2021 Previous Year Paper Solution | Morning Shift Junior Engineer

uprvnl exam paper

Question 1: In circuit breakers making capacity = _____________ X Symmetrical breaking capacity.

a. 2.97
b. 1.82
c. 2.55
d. 4.12

Answer: 2.55


Question 2: Calculate the rectification efficiency of half wave rectifier if input power to rectifier is 150 W and power obtained is 90 W.

a. 60%
b. 50%
c. 40%
d. 80%

Answer: 60%


Question 3: Which of the following are types of URL?.

a. Relative and Dynamic
b. Absolute and Relative
c. Static and Dynamic
d. Absolute and Dynamic

Answer: Absolute and Relative


Question 4: Which of the following represents the terminals of a MOSFET?

a. Drain, Collector and Gate
b. Drain, Collector and Base
c. Emitter, Collector and Base
d. Drain, Source and Gate

Answer: Drain, Source and Gate


Question 5: The insulation resistance of motors and other equipment can be expressed as:

a. (30 x rated phase to phase voltage)/(1000 + 2 x rated power)
b. (30 x rated phase to phase voltage)/(5000 + 2 x rated power)
c. (10 x rated phase to phase voltage)/(1000 + 2 x rated power)
d. (20 x rated phase to phase voltage)/(1000 + 2 x rated power)

Answer: (20 x rated phase to phase voltage)/(1000 + 2 x rated power)


Question 6: Danger boards should be at a height of _________ meters from ground.

a. 1
b. 4
c. 3
d. 2

Answer: 3


Question 7: Which of the following is ferromagnetic.

a. Oxygen
b. Cobalt
c. Glass
d. Rubber

Answer: Cobalt


Question 8: According to IS 4648:1968, ceiling fans should be hung at least the floor.

a. 6.75
b. 5.75
c. 3.75
d. 2.75

Answer: 2.75


Question 9: The 8086 is a ____________ bit integer processor.

a. 20 bit
b. 8 bit
c. 16 bit
d. 18 bit

Answer: 16 bit


Question 10: Dielectric loss is proportional to:

a. Frequency
b. (Frequency)2
c. (Frequency)3
d. (Frequency)1/2

Answer: Frequency


Question 11: Which of the following is the CORRECT full form of SCADA?

a. Super Control And Data Acquisition
b. Supervisory Computation And Data Acquisition
c. Supervisory Control And Data Acquisition
d. Stand Control And Data Acquisition

Answer: Supervisory Control And Data Acquisition


Question 12: A penstock is a constituent of a power plant.

a. Steam power plant
b. Nuclear power plant
c. Hydro power plant
d. Diesel power plant

Answer: Hydro power plant


Question 13: In a power sub-circuit, the maximum connected load is:

a. 6000 W
b. 12000 W
c. 3000 W
d. 9000 W

Answer: 3000 W


Question 14: CMOS generally stands for:

a. Super Control And Data Acquisition

a. Complex MOSFET
b. Conventional MOSFET
c. Commercial MOSFET
d. Complementary MOSFET

Answer: Complementary MOSFET


Question 15: Running cost of a power plant is minimum.

a. Diesel
b. Hydro
c. Steam
d. Nuclear

Answer: Hydro


Question 16: The resistance of an ideal conductor is ___________.

a. 1 ohm
b. infinite
c. 100 ohm
d. zero

Answer: Zero


Question 17: The pitch factor of full pitch alternator is:

a. 0.7
b. 0.5
c. 1
d. 0

Answer: 1


Question 18: The unit of electrostatic charge is:

a. Ampere.second
b. Coulomb/second
c. Ampere
d. Ampere/second

Answer: Ampere.second


Question 19: The given truth table is for a(n) gate.

a. OR gate
b. AND gate
c. XOR gate
d. XNOR gate

Answer: AND gate


Question 20: Which of the following does NOT represents a component of SCADA system?

a. PLC
b. Sparger controller
c. Human-machine interface
d. RTU

Answer: Sparger controller


Question 21: Which of the following is a sign of danger associated with overhead installations?

Answer: C


Question 22: The given image is the symbol of :

a. DIAC
b. BJT
c. TRIAC
d. SCR

Answer: TRIAC


Question 23: The Curie of temperature of Nickle (in Kelvin) is:

a. 543
b. 987
c. 324
d. 627

Answer: 627


Question 24: The potential difference between the feet of a person standing in a sub station with one step during the flow of earth fault current is called :

a. magnetic potential
b. step potential
c. touch potential
d. capacitive potential

Answer: Step Potential


Question 25: For a two bus system, which of the following conditions should follow loss coefficient?

a. B12 =0.002, B21= -0.006
b. B12 =0.002, B21= 0.002
c. B12 = -0.002, B21= 0.002
d. B12 =0.006, B21= 0.002

Answer: b. B12 =0.002, B21= 0.002


Question 26: Calculate the power of a lamp if it consumes 500 J in 20 seconds.

a. 15 W
b. 25 W
c. 20 W
d. 50 W

Answer: b. 25 W


Question 27: Which of the following is used for switching and lightning surge protection?

a. Surge arrestor
b. Insulator
c. Circuit breaker
d. Relay

Answer: Surge Arrestor


Question 28: The scale of a Megger is generally ranges from _________.

a. (0 – 1000) Ω
b. (0 – 10000) Ω
c. (0 – 100) Ω
d. (0 – infinity) Ω

Answer: d. (0 – infinity) Ω


Question 29: When a bulb of 50W is connected across 200V, the energy consumed in 1 minute is ____________ Watt-sec.

a. 3000
b. 500
c. 300
d. 50

Answer: a. 3000


Question 30: A capacitive divider of ratio C2 : C1 = 149 : 1 is used to measure high voltage. If the Voltage measured across C2 is 10 V then the voltage across C1 (neglect the resistance) is:

a. 1.49kV
b. 10 kV
c. 2.12 kV
d. 15 kV

Answer: a. 1.49kV


Question 31: The decimal equivalent of octal number (145)8 is:.

a. (101)10
b. (165)10
c. (196)10
d. (353)10

Answer: a. (101)10


Question 32: Which one of the following statements is not related in case of an electric shock?.

a. give the unconscious person anything to eat or drink
b. unplug the supply
c. do not leave the unconscious person alone
d. protect yourself and pull the victim

Answer: a. give the unconscious person anything to eat or drink


Question 33: The average resistance of a human body is about:

a. 150000 Ω
b. 100000 Ω
c. 50000 Ω
d. 1000 Ω

Answer: d. 1000 Ω


Question 34: The fusing factor of a standard duty cartridge’s fuse is:

a. 1.45
b. 3.45
c. 0.45
d. 2.45

Answer: a. 1.45


Question 35: The given figure is an example of a ______ crystal.

a. Face centered cubic crystal
b. Simple monoclinic crystal
c. Body-Centered cubic crystal
d. Simple cubic crystal

Answer: c. Body-Centered cubic crystal


Question 36:Which of the following is not a anti-virus software?

a. Kaspersky
b. Norton
c. Quick heal
d. Trojan

Answer: d. Trojan


Question 37: Which of the following is the CORRECT HTML tag for the smallest size heading?

a. <h6>
b. <h1>
c. <h3>
d. <head>

Answer: a. <h6>


Question 38: CPU stands for:

a. Central programming Unit
b. Command Programming Unit
c. Central processing Unit
d. Command Processing Unit

Answer: c. Central processing Unit


Question 39: If voltage across each disk insulator in a string is equal then calculate the string efficiency of the string.

a. 90%
b. 50%
c. 100%
d. 75%

Answer: c. 100%


Question 40: Which of the following is used in the brush of DC motor?

a. Copper
b. Iron
c. Carbon
d. Aluminum

Answer: c. Carbon


Question 41: The command to copy in Microsoft Word in computer is:

a. Ctrl + V
b. Ctrl + F
c. Ctrl + C
d. Ctrl + X

Answer: c. Ctrl + C


Question 42: Determine the damping ratio of the given transfer function. C(s) = 4/(s + 19)(s + 4)

a. 9/12
b. 1
c. 13/12
d. 12/13

Answer: c. 13/12


Question 43: Which of the following is the CORRECT statement with respect to energy?

a. Energy can be destroyed
b. Energy can be stored
c. Energy can be created
d. Energy can be transformed one form to another

Answer: d. Energy can be transformed one form to another


Question 44: Carbon zinc cells is also known as:

a. Leclanche cell
b. Lead acid
c. Mercury cell
d. Alkaline cell

Answer: a. Leclanche cell


Question 45: Which of the following relation is TRUE for progressive winding of a DC machine?

a. YF = YB – 2
b. YF = YB + 1
c. YF = YB – 1
d. YF = YB + 2

Answer: a. YF = YB – 2


Question 46: A wire-gauge is used to measure :

a. Thickness of insulation of a wire
b. Length of a wire
c. Diameter of a wire
d. Resistance of a wire

Answer: c. Diameter of a wire


Question 47: In a hydroelectric power plant, which of the following is used to discharge surplus water on the downstream side of the dam?

a. Penstock
b. Surge tank
c. Condenser
d. Spillways

Answer: d. Spillways


Question 48: A moving coil instrument gives full scale deflection of 6mA when there is a potential difference of 60mV across the terminal. Calculate the series resistance for a full scale reading of 600mV.

a. 100 Ω
b. 1000 Ω
c. 90 Ω
d. 9 Ω

Answer: c. 90 Ω


Question 49: A tuned amplifier has resonant frequency 1000 kHz and bandwidth is 25 kHz. The quality (Q) factor of this amplifier is :

a. 40
b. 975
c. 1/40
d. 25000

Answer: a. 40


Question 50: There are some liquids in which a passage of electric current is accompanied by chemical changes. This effect is known as the ________ effect of electric current. :

a. thermal
b. mechanical
c. chemical
d. physical

Answer: c. chemical


Question 51: As per occupational hazards mechanical hazard is:

a. open wire
b. unguarded machinery
c. short circuit
d. current leakage

Answer: b. unguarded machinery


Question 52: Calculate the transfer function of the system shown in the given figure

a. G/(1 + 2G)
b. G/(1 – 2G)
c. 2G/(1 + 2G)
d. 2G/(1 – 2G)

Answer: b. G/(1 – 2G)


Question 53: A vacuum circuit breaker can be used in which voltage range

a. 11-33 kV
b. 22-66 kV
c. 22-33 kV
d. 11-66 kV

Answer: a. 11-33 kV


Question 54: MHSCP stands for:

a. Minimum hemi spherical continuous power
b. Minimum hemi spherical candlepower
c. Mean hemi spherical candle power
d. Mean horizontal spherical candle power

Answer: c. Mean hemi spherical candle power


Question 55: Short circuit test of transformer gives the information of:

a. copper loss
b. hysteresis loss
c. iron loss
d. eddy current loss

Answer: a. copper loss


Question 56: Calculate the slip of 4 pole induction motor if speed is 1450 rpm and supply frequency is 50 Hz.

a. 0.033
b. 0.05
c. 0.067
d. 0.015

Answer: a. 0.033


Question 57: Which of the following is a protective device?

a. Insulator
b. Fuse
c. Relay
d. Synchronous condenser

Answer: b. Fuse


Question 58: The simplified version of the expression X= (A + B).(A + C) is:

a. A + AB
b. A + BC
c. AB + BC + CA
d. B + AC

Answer: b. A + BC


Question 59: Which of the following is a semiconductor?

a. Neon
b. Carbon
c. Gold
d. Silicon

Answer: d. Silicon


Question 60: NaCl is:

a. Hexagonal crystal structure
b. Tetragonal crystal structure
c. Orthorhombic crystal structure
d. Cubic crystal structure

Answer: d. Cubic crystal structure


Question 61: Which of the following is the symbol of an isolator generally used in a sing line diagram?

Answer: d.


Question 62: Medium level language is:

a. Python
b. Java
c. C
d. C++

Answer: c. C & d. C++


Question 63: The closed loop gain of the given amplifier for R1 = 5.5 kΩ and R2 = 3.3 kΩ is:

a. 0.60
b. 2.66
c. 1.60
d. 1.00

Answer: c. 1.60


Question 64: If a signal has a time period of 25 msec, then calculate the frequency of the signal.

a. 25Hz
b. 50Hz
c. 60Hz
d. 40Hz

Answer: d. 40Hz


Question 65: Aluminum is a ____________ material.

a. Ferromagnetic
b. Ferrimagenetic
c. Diamagenetic
d. Parammagenetic

Answer: d. Parammagenetic


Question 66: Which of the following power plant required the highest capital cost?

a. Hydro power plant
b. Steam power plant
c. Nuclear power plant
d. Diesel power plant

Answer: a. Hydro power plant


Question 67: 2’s complement of the binary number (1010101)2 is :

a. (1110011)2
b. (1101010)2
c. (0101010)2
d. (0101011)2

Answer: d. (0101011)2


Question 68: The example of macro virus is

a. Michelangelo
b. CoolWebSearch
c. Zango
d. Wazzo

Answer: d. Wazzo


Question 69: 1 GB is equal to:

a. 256 MB
b. 1000 MB
c. 1024 MB
d. 100 MB

Answer: c. 1024 MB


Question 70: At a unity factor, the armature reaction of an alternator is:

a. Demagnetizing
b. Magnetizing
c. Distorting
d. Partly distorting

Answer: c. Distorting


Question 69: A/An _____________ cell is a type of secondary cell.

a. lead acid cell
b. Alkaline cell
c. silver oxide cell
d. Mercury cell

Answer: a. lead acid cell


Question 69: As per safety norms, which of the following condition should be fulfill for the selection of CORRECT capacity fuse?

a. Allow excess current flow
b. Protect fuse instead of equipment
c. Man and machine endangers
d. Protect equipment against overcurrent

Answer: d. Protect equipment against overcurrent


Question 70: At a unity factor, the armature reaction of an alternator is:

a. Demagnetizing
b. Magnetizing
c. Distorting
d. Partly distorting

Answer: c. Distorting


Question 71: To avoid a break in a circuit due to one lamp failure, which lighting circuit should be chosen in house wiring?

a. Parallel
b. A part of the circuit connected in series and rest of the part connected parallel
c. series
d. Both series and Parallel

Answer: a. Parallel


Question 72: Which of the following represents the Correct Boolean representation of the given PLC Program?

a. C(AB + D)
b. D(AB + C)
c. ABC + D
d. D(AC + B)

Answer: a. C(AB + D)


Question 73: A black body always emits maximum energy in the visible spectrum when heated to:

a. 3520 °C
b. 5520 °C
c. 6520 °C
d. 4520 °C

Answer: c. 6520 °C


77 53:13

Top 50 8051 Microcontroller MCQ – 2

Hi all, This is second part of 8051 microcontroller multiple choice questions series. In this MCQ series i have explained top 50 multiple choice questions. If you want to see more questions on 8051 microcontroller then check my previous post here.

This series will help in competitive exam like UPPCL- JE, SSC JE, RSEB, RRB and all competitive exam.

Please checkout all multiple choice questions like microcontroller, Power electronics, PLC and SCADA and 8086 microprocessor here. later I will add more questions in this series. So more update check frequently.

Question 1 Which of the following is the default value of stack once after the system undergoes the reset condition?

  • 08H
  • 09H
  • 00H
  • 07H

Answer: 07H

Question 2 Which of the following commands are used for addressing the off-chip data and associated codes respectively by data pointer?

  • MOVC & MOVY
  • MOVY & MOVB
  • MOVZ & MOVA
  • MOVX & MOVC

Answer: MOVX & MOVC

Question 3 Which of the following is the bit addressing range of addressable individual bits over the on-chip RAM?

  • 00H to 7FH
  • 01H to 7FH
  • 00H to FFH
  • 80H to FFH

Answer: 00H to 7FH

Question 4 ……….. signal control the flow of data

  • DTR
  • RTS
  • Both 1 & 2
  • None of the above

Answer: Both 1 & 2

Question 5 Register that is used to holds the memory address of the next instruction to be executed is

  • Program Memory
  • Program Counter
  • Control Unit
  • Instruction decoder

Answer: Program Counter

Question 6 If we say microcontroller is 8-bit then here 8-bit denotes size of

  • Data Bus
  • ALU
  • Control Bus
  • Address Bus

Answer: ALU

Question 7 Why microcontrollers are not called general purpose computers?

  • Because they have built in RAM and ROM
  • Because they design to perform dedicated task
  • Because they are cheap
  • Because they consume low power

Answer: Because they design to perform dedicated task

Question 8 What is the most appropriate criterion for choosing the right microcontroller of our choice?

  • Speed
  • Availability
  • Ease with the product
  • All of the mentioned

Answer: All of the mentioned

Question 9 A microcontroller at-least should consist of

  • RAM, ROM, I/O ports and timers
  • CPU, RAM, I/O ports and timers
  • CPU, RAM, ROM, I/O ports and timers
  • CPU, ROM, I/O ports and timer

Answer: CPU, RAM, ROM, I/O ports and timers

Question 10 AT89C2051 has RAM of

  • 128 bytes
  • 256 bytes
  • 64 bytes
  • 512 bytes

Answer: 128 bytes

Question 11 If we push data onto the stack then the stack pointer

  • Increases with every push
  • Decreases with every push
  • Increases & decreases with every push
  • None of the mentioned

Answer: Increases with every push

Question 12 How are the status of the carry, auxiliary carry and parity flag affected if the write instruction

MOV A,#9C

ADD A,#64H

  • CY=0,AC=0,P=0
  • CY=1,AC=1,P=0
  • CY=0,AC=1,P=0
  • CY=1,AC=1,P=1

Answer: CY=1,AC=1,P=0

Question 13 JZ, JNZ, instructions checked content of _______ register

  • DPTR
  • B
  • A
  • PSW

Answer: A

Question 14 Unlike microprocessors, microcontrollers make use of batteries because they have

  • high power dissipation
  • low power consumption
  • low voltage consumption
  • low current consumption

Answer: low power consumption

Question 15 Are PUSH and POP instructions are a type of CALL instructions?

  • yes
  • no
  • none of the mentioned
  • cant be determined

Answer: no

Question 16 What is the time taken by one machine cycle if crystal frequency is 20MHz?

  • 1.085 micro seconds
  • 0.60 micro seconds
  • 0.75 micro seconds
  • 1 micro seconds

Answer: 0.60 micro seconds

Question 17 What is the meaning of the instruction MOV A,05H?

  • Data 05H is stored in the accumulator
  • Fifth bit of accumulator is set to one
  • Address 05H is stored in the accumulator
  • None of the mentioned

Answer: Address 05H is stored in the accumulator

Question 18 The upper 128 bytes of an internal data memory from 80H through FFH usually represent _______

  • General-purpose registers
  • Special function registers
  • Stack pointers
  • Program counters

Answer: Special function registers

Question 19 Which of the ports act as the 16 bit address lines for transferring data through it?

  • PORT 0 and PORT 1
  • PORT 1 and PORT 2
  • PORT 0 and PORT 2
  • PORT 1 and PORT 3

Answer: PORT 0 and PORT 2

Question 20 Which operations are performed by the bit manipulating instructions of Boolean processor?

  • Complement bit
  • Set bit
  • Clear bit
  • All of the above

Answer: All of the above

Question 21 Which location specify the storage/loading of vector address during the interrupt generation?

  • Stack Pointer
  • Program Counter
  • Data Pointer
  • All of the above

Answer: Program Counter

Question 22 Which special function register play a vital role in the timer/counter mode selection process by allocating the bits in it?

  • TMOD
  • TCON
  • SCON
  • PCON

Answer: TMOD

Question 23 Why is it not necessary to specify the baud rate to be equal to the number of bits per second?

  • Because each bit is preceded by a start bit & followed by one stop bit
  • Because each byte is preceded by a start byte & followed by one stop byte
  • Because each byte is preceded by a start bit & followed by one stop bit
  • Because each bit is preceded by a start byte &followed by one stop byte

Answer: Because each byte is preceded by a start bit & followed by one stop bit

Question 24 Which is not the feature of 16-bit microcontroller?

  • Large program & data memory spaces
  • High speed
  • I/O Flexibility
  • Limited Control Applications

Answer: Limited Control Applications

Question 25 At what PIN number, there is EA pin which stands for External Access input?

  • PIN 28
  • PIN 29
  • PIN 30
  • PIN 31

Answer: PIN 31

Question 26 How does the microcontroller communicate with the external peripherals / memory?

  • Via I/O ports
  • Via register array
  • Via memory
  • All of the above

Answer: Via I/O ports

Question 27 What is the order decided by a processor or the CPU of a controller to execute an instruction?

  • decode, fetch, execute
  • execute, fetch, decode
  • fetch, execute, decode
  • fetch, decode, execute

Answer: fetch, decode, execute

Question 28 How are the performance and the computer capability affected by increasing its internal bus width?

  • It increases and turns better
  • It decreases
  • Remains the same
  • Internal bus width doesn’t affect the performance in any way

Answer: It increases and turns better

Question 29 How many bytes of bit addressable memory is present in 8051 based microcontrollers?

  • 8 bytes
  • 32 bytes
  • 16 bytes
  • 128 bytes

Answer: 16 bytes

Question 30 MOV A, @ R1 will:

  • Copy R1 to the accumulator
  • Copy the accumulator to R1
  • Copy the contents of memory whose address is in R1 to the accumulator
  • Copy the accumulator to the contents of memory whose address is in R1

Answer: Copy the contents of memory whose address is in R1 to the accumulator

Question 31 What is the file extension is used to load in a microcontroller to execute an instruction?

  • .doc
  • .c
  • .txt
  • .hex

Answer: .hex

Question 32 Which control signal/s is/are generated by timing and control unit of 8051 microcontroller in order to access the off-chip devices apart from the internal timings?

  • ALE
  • PSEN
  • RD & WR
  • All of the above

Answer: All of the above

Question 33 What is internal RAM memory of 8051 microprocessor?

  • 32 bytes
  • 64 bytes
  • 128 bytes
  • 256 bytes

Answer: 128 bytes

Question 34 How many timers/counter 8051 16-bit microprocessor have?

  • 1
  • 2
  • 5
  • 8

Answer: 2

Question 35 Which operator is the most important while assigning any instruction as register indirect instruction?

  • $
  • #
  • @
  • &

Answer: @

Question 36 Which of the following comes under the indexed addressing mode?

  • MOVX A, @DPTR
  • MOVC @A+DPTR,A
  • MOV A,R0
  • MOV @R0,A

Answer: MOVC @A+DPTR,A

Question 37 When we add two numbers the destination address must always be.

  • Some immediate data
  • Any register
  • Accumulator
  • Memory

Answer: Accumulator

Question 38 In 8 bit signed number operations, OV flag is set to 1 if:

  • a carry is generated from D7 bit
  • a carry is generated from D3 bit
  • a carry is generated from D7 or D3 bit
  • a carry is generated from D7 or D6 bit

Answer: a carry is generated from D7 or D6 bit

Question 39 Auto reload mode is allowed in which mode of the timer?

Mode 0
Mode 1
Mode 2
Mode 3

Answer: Mode 2

Question 40 What is the frequency of the clock that is being used as the clock source for the timer?

  • Some externally applied frequency f’
  • Controller’s crystal frequency f
  • Controller’s crystal frequency /12
  • Externally applied frequency/12

Answer: Controller’s crystal frequency /12

Question 41 Which of the following signal control the flow of data?

  • RTS
  • DTR
  • RTS & DTR
  • None of the mentioned

Answer: RTS

Question 42 Which of the following best describes the use of framing in asynchronous means of communication?

  • It binds the data properly
  • It tells us about the start and stops of the data to be transmitted or received
  • It is used for error checking
  • It is used for flow control

Answer: It tells us about the start and stops of the data to be transmitted or received

Question 43 What is the difference between UART and USART communication?

  • They are the names of the same particular thing, just the difference of A and S is there in it
  • One uses asynchronous means of communication and the other uses synchronous means of communication
  • One uses asynchronous means of communication and the other uses asynchronous and synchronous means of communication
  • One uses angular means of the communication and the other uses linear means of communication

Answer: One uses asynchronous means of communication and the other uses asynchronous and synchronous means of communication

Question 44 Which devices are specifically being used for converting serial to parallel and from parallel to serial respectively?

  • Timers
  • Counters
  • Registers
  • Serial communication

Answer: Registers

Question 45 Which pin of the external hardware is said to exhibit INT0 interrupt?

  • pin no 10
  • pin no 11
  • pin no 12
  • pin no 13

Answer: pin no 12

Question 46 Which bit of the IE register is used to enable TxD/RxD interrupt?

  • IE.D5
  • IE.D2
  • IE.D3
  • IE.D4

Answer: IE.D4

Question 47 When an interrupt is enabled, then where does the pointer moves immediately after this interrupt has occurred?

  • to the next instruction which is to be executed
  • to the first instruction of ISR
  • to a fixed location in memory called interrupt vector table
  • to the end of the program

Answer: To a fixed location in memory called interrupt vector table

Question 48 After RETI instruction is executed then the pointer will move to which location in the program?

  • next interrupt of the interrupt vector table
  • immediate next instruction where interrupt is occurred
  • next instruction after the RETI in the memory
  • none of the mentioned

Answer: To a fixed location in memory called interrupt vector table

Question 49 Which pin of the LCD is used for adjusting its contrast?

  • pin no 1
  • pin no 2
  • pin no 3
  • pin no 4

Answer: pin no 3

Question 50 For writing commands on an LCD, RS bit is

set
reset
set & reset
none of the mentioned

Answer: Reset


FAQ

What is Microcontroller?

Microcontroller is a combination of two words micro and controller, Micro means small in size and controller means a device that can control the operation of any system. So we can say that a microcontroller is a microprocessor with integrated peripherals.

What is the order decided by a processor or the CPU of a controller to execute an instruction?

First instruction is fetched from Program Memory, then fetching, instruction is decoded to generate control signals to perform the intended task. After decoding, instruction is executed and the complete intended task of that particular instruction.

How are the performance and the computer capability affected by increasing its internal bus width?

As the bus width increases, the number of bits carried by bus at a time increases as a result of which the total performance and computer capability increases.

How many bytes of bit addressable memory is present in 8051 based microcontrollers?

8051 microcontrollers have 16 bytes of bit addressable memory.

How many timers/counter 8051 microcontroller have?

8051 Microcontroller 8051 have 2 timers/counter.

When was intel design first 8051 microcontroller?

8051 microcontroller is designed by Intel in 1981. It is an 8-bit microcontroller

Why is CHMOS technology preferred over HMOS technology for designing the devices of MCS-51 family?

Micro Controllers are made by using the concept of VLSI technology. So here, CMOS based logic gates are coupled together by this technique that consumes low power.

8051 series has how many 16 bit registers?

8051 microcontroller has two 16 bit registers DPTR and PC.

8051 microcontrollers are manufactured by which of the following companies?

8051 microcontrollers are manufactured by Intel, Atmel, Philips/Signetics, Infineon, Dallas Semi/Maxim.

Which IO Port can be used for higher address byte with addresses A8-A15?

PORT2 : This port can be used for higher address byte with addresses A8-A15. When no memory is added then this port can be used as a general input/output port similar to Port 1.

Power Electronics MCQ serires 1

Power electronics MCQ Series – 1

Top 20 questions of power electronics. For explanation of each answer you can watch my video

Question 1: A thyristor is basically

  • PNPN device
  • A combination of diac and triac
  • A set of SCRs
  • A set of SCR, diac and a triac

Answer: PNPN device

Question 2: A silicon controlled rectifier (SCR) is a

  • Unijunction device
  • Device with three junction
  • Device with four junction
  • None of the above

Answer: Device with three junction

Question 3: A thyristor equivalent of a thyratron tube is a

  • Diac
  • Triac
  • Silicon controlled rectifier
  • None of the above

Answer: Silicon controlled rectifier

Question 4: An SCR is made up of silicon because

  • Silicon has large leakage current than germanium
  • Silicon has small leakage current than germanium
  • Silicon has small leakage voltage than germanium
  • Silicon has large leakage voltage than germanium

Answer: Silicon has small leakage current than germanium

Question 5: An SCR is considered to be a semi controlled device because

  • It can be turned OFF but not ON with a gate pulse.
  • It conducts only during one half cycle of an alternating current wave.
  • It can be turned ON but not OFF with a gate pulse.
  • It can be turned ON only during one half cycle of an AC.

Answer: It can be turned ON but not OFF with a gate pulse.

Question 6: Which statement is true for latching current ?

  • It is related to turn off process of the device.
  • It is related to conduction process of device.
  • It is related to turn on process of the device.
  • Both C and D.

Answer: It is related to turn on process of the device.

Question 7: If holding current of a thyristor is 2 mA then latching current should be

  • 0.01 A.
  • 0.002 A.
  • 0.009 A.
  • 0.004 A

Answer: 0.004 A

Question 8: In reverse blocking mode of a thyristor

  • junction J2 is in reverse bias and J1, J3 is in forward bias.
  • junction J3 is in forward bias and J1, J2 in reverse bias.
  • junction J1, J3 is in reverse bias and J2 is in forward bias.
  • junction J1 and J2 is in forward bias and J3 is in reverse bias.

Answer: junction J1, J3 is in reverse bias and J2 is in forward bias.

Question 9: During the commutation period in 3 phase converter, overlap time is

  • Dependent on the load current
  • Dependent on the voltage
  • Dependent on both the load current and load voltage behind the short circuit current
  • Independent on both the load current and load voltage

Answer: Dependent on both the load current and load voltage behind the short circuit current

Question 10: A UJT has ___________.

  • Two pn junctions
  • One pn junction
  • Three pn junctions
  • None of the above

Answer: One pn junction

Question 11: The UJT may be used as ___________.

  • Am amplifier
  • A sawtooth generator
  • A rectifier
  • None of the above

Answer: A sawtooth generator

Question 12: The fig. below represents a

  • Triac thyristor
  • Diac trigger
  • Diode rectifier
  • None of the above

Answer: Diac trigger

Question 13: A diac has ______________ pn junctions.

  • One
  • Two
  • Three
  • Four

Answer: Two

Question 14: What is a TRIAC?

  • Two thyristors connected in series mode
  • Two thyristors connected in parallel mode
  • Two thyristors connected in anti parallel mode
  • Two transistors connected in anti parallel mode

Answer: Two transistors connected in anti parallel mode

Question 15: For an SCR, dv/dt protection is achieved through

  • RC across SCR
  • RL in series with SCR
  • L across SCR
  • L in series with SCR

Answer: RC across SCR

Question 16: Power diode is __________

  • a three terminal semiconductor device
  • a two terminal semiconductor device
  • a four terminal semiconductor device
  • a three terminal analog device

Answer: a two terminal semiconductor device

Question 17: An ideal power diode must have

  • low forward current carrying capacity
  • large reverse breakdown voltage
  • high ohmic junction resistance
  • high reverse recovery time

Answer:

Question 18: A diode is said to be forward biased when the

  • cathode is positive with respect to the anode
  • anode is positive with respect to the cathode
  • anode is negative with respect to the anode
  • both cathode & anode are positive

Answer: anode is positive with respect to the cathode

Question 19: To make a signal diode suitable for high current & high voltage carrying applications with minimum losses, ________

  • a lightly doped n layer is grown between the two p & n layers
  • a heavily doped n layer is grown between the two p & n layers
  • a lightly doped p layer is grown between the two p & n layers
  • a heavily doped p layer is grown between the two p & n layers

Answer: a lightly doped n layer is grown between the two p & n layers

Question 20: Which one of the following statements is TRUE for an ideal power diode?

  • Reverse recovery time is non zero and reverse saturation current is zero
  • Forward voltage drop is zero and reverse saturation current is non zero
  • Forward voltage drop is non zero and reverse recovery time is zero
  • Forward voltage drop is zero and reverse recovery time is zero

Answer: Forward voltage drop is non zero and reverse recovery time is zero


FAQ

What is a thyristor ?

Thyristor is also called a silicon-controlled rectifier (SCR), it is basically a four-layer three-junction pnpn device. It has three terminals: anode, cathode, and gate.
Thyristor is basically an electronic switching device which can remain in conducting (on) and nonconducting state. However, it is a unidirectional device and can conduct only in one direction like a diode. The switching state of the device can be controlled by one of its terminals.

What is silicon controlled rectifier (SCR)?

The thyristor is also called a silicon-controlled rectifier (SCR), it is basically a four-layer three-junction pnpn device. It has three terminals: anode, cathode, and gate.
The silicon control rectifier (SCR) consists of four layers of semiconductors, which form NPNP or PNPN structures, having three P-N junctions labeled J1, J2 and J3, and three terminals.

Which thyristor is equivalent of a thyratron tube?

SCR, The thyratron is a type of gas-filled tube which is used as a high voltage electrical switch and a controlled rectifier.

Why SCR is considered to be a semi controlled device ?

During positive half cycle SCR is in forward blocking mode. By applying gate pulse the SCR can be turned ON during forward blocking mode. But SCR can not be turned OFF by applying gate pulse. It automatically turns off when anode current is below the Holding current. That is why it is called semi controlled rectifier.

What is latching current?

Latching current is the minimum required anode current to turn on SCR. Latching current is 2 or 3 times of holding current

What is holding current?

Holding current is the minimum anode current below which SCR get turn off. Holding current is 2 or 3 times less than latching current.

What is reverse blocking mode of a thyristor?

When a negative voltage is applied to the anode and a positive voltage to the cathode, the SCR is in reverse blocking mode, making J1 and J3 reverse biased and J2 forward biased.
The device behaves as two reverse-biased diodes connected in series. A small leakage current flows. This is the reverse blocking mode.

What is unijunction transistor (UJT)?

A unijunction transistor (UJT) is a three-lead electronic semiconductor device with only one junction that acts exclusively as an electrically controlled switch. The UJT is not used as a linear amplifier.

What is power diode?

It has two terminals anode and cathode same as that of a ordinary diode. In fact, a power diode is nothing but a signal diode with a extra layer.


#1 Basic Electronics MCQ

20 Basic electronics MCQ’s

Question 1 The most commonly used semiconductor is ………

  • Germanium
  • Silicon
  • Carbon
  • Sulphur

Answer – Silicon

Question 2 The resistivity of a pure silicon is about ……………

  • 100 Ω cm
  • 6000 Ω cm
  • 3 x 105 Ω m
  • 6 x 10-8 Ω cm

Answer – 6000 Ω cm

Question 3 A semiconductor is formed by ……… bonds.

  • Covalent
  • Electrovalent
  • Co-ordinate
  • None of the above

Answer – Covalent

Question 4 A pentavalent impurity has ………. Valence electrons

  • 3
  • 5
  • 4
  • 6

Answer – 5

Question 5 A semiconductor has generally ……………… valence electrons.

  • 2
  • 3
  • 6
  • 4

Answer – 4

Question 6 A hole in a semiconductor is defined as …………….

  • A free electron
  • The incomplete part of an electron pair bond
  • A free proton
  • A free neutron

Answer – The incomplete part of an electron pair bond

Question 7 Addition of trivalent impurity to a semiconductor creates many ……..

  • Holes
  • Free electrons
  • Valence electrons
  • Bound electrons

Answer – Holes

Question 8 Addition of pentavalent impurity to a semiconductor creates many ……..

  • Free electrons
  • Holes
  • Valence electrons
  • Bound electrons

Answer – Free electrons

Question 9 In a semiconductor, current conduction is due to …

  • Only holes
  • Only free electrons
  • Holes and free electrons
  • None of the above

Answer – Holes and free electrons

Question 10 The battery connections required to forward bias a pn junction are ……

  • +ve terminal to p and –ve terminal to n
  • -ve terminal to p and +ve terminal to n
  • -ve terminal to p and –ve terminal to n
  • None of the above

Answer – +ve terminal to p and –ve terminal to n

Question 11 A forward biased pn junction diode has a resistance of the order of

  • Ω
  • None of the above

Answer – Ω

Question 12 The barrier voltage at a pn junction for germanium is about ………

  • 5 V
  • 3 V
  • Zero
  • 0.3 V

Answer – 0.3 V

Question 13 A reverse bias pn junction has …………

  • Very narrow depletion layer
  • Almost no current
  • Very low resistance
  • Large current flow

Answer – Almost no current

Question 14 A pn junction acts as a ……….

  • Controlled switch
  • Bidirectional switch
  • Unidirectional switch
  • None of the above

Answer – Unidirectional switch

Question 15 In the depletion region of a pn junction, there is a shortage of ……..

  • Acceptor ions
  • Holes and electrons
  • Donor ions
  • None of the above

Answer – Holes and electrons

Question 16 The leakage current across a pn junction is due to …

  • Minority carriers
  • Majority carriers
  • Junction capacitance
  • None of the above

Answer – Minority carriers

Question 17 When the temperature of an extrinsic semiconductor is increased, the pronounced effect is on……

  • Junction capacitance
  • Minority carriers
  • Majority carriers
  • None of the above

Answer – Minority carriers

Question 18 With forward bias to a pn junction , the width of depletion layer ………

  • Decreases
  • Increases
  • Remains the same
  • None of the above

Answer – Decreases

Question 19 At room temperature, an intrinsic semiconductor has ……….

  • Many holes only
  • A few free electrons and holes
  • Many free electrons only
  • No holes or free electron

Answer – A few free electrons and holes

Question 20 The leakage current in a pn junction is of the order of

  • Aa
  • mA
  • kA
  • µA

Answer – µA


Topics


FAQ – Frequently ask questions

Which is most commonly used semiconductor?

Silicon, Silicon is the most used semiconductor in power electronic components like diodes, thyristors, IGBT, MOSFET transistors.

How Semiconductor form?

A semiconductor is form by covalent bond with his neighboring atoms.
In covalent bonding each valence electron is shared by two atoms

How many valence electrons in a pentavalent impurity atom?

In pentavalent impurity atom 5 valence electron in their outer most cell

How pn junction acts?

pn junction acts as a unidirectional switch

In a pn junction leakage current is due to

Minority carriers

#4 Top 50 PLC and SCADA MCQ

Important 50 Multiple Choice Question based on PLC and SCADA


Question 1: What is the full form of SCADA?

  • Supervisory Control and Document Acquisition
  • Supervisory Control and Data Acquisition
  • Supervisory Column and Data Assessment
  • Supervisory Column and Data Assessment

Answer: Supervisory Control and Data Acquisition

Question 2: DCS is a ______

  • Distributed Control System
  • Data Control System
  • Data Column System
  • Distributed Column System

Answer: Distributed Control System

Question 3 The control in SCADA is _____________

  • Online control
  • Direct control
  • Supervisory control
  • Automatic control

Answer: Supervisory control

Question 4 What is SCADA?

  • Software
  • Process
  • System
  • Hardware

Answer: Process

Question 5 Which of the following is not the component of a SCADA system?

  • Database server
  • I/O system
  • PLC controller
  • Sparger controller

Answer: Sparger controller

Question 6 When did the SCADA start?

  • 1980s
  • 1990s
  • 1970s
  • 1960s

Answer:1960s

Question 7 When did Windows become the world standard operating system?

  • 1980s
  • 1990s
  • 1970s
  • 1960s

Answer: 1990s

Question 8 How many levels are present in a complex SCADA system?

  • 3 – levels
  • 5 – levels
  • 4 – levels
  • 6 – levels

Answer: 4 – levels

Question 9 What is the full form of RAID

  • Redundant Array of Independent Drives
  • Redundant Array of Inexpensive Disks
  • Redundant Array of Independent Disks
  • All of the above

Answer: All of the above

Question 10 Which of the following is used for centralized network databases?

  • RAID 2
  • RAID 5
  • RAID 1
  • RAID 2

Answer: RAID 5

Question 11 Which of the following is the heart of a SCADA system?

  • PLC
  • HMI
  • Alarm task
  • I/O task

Answer: I/O task

Question 12 Which of the following is an example of the SCADA system?

  • Emerson Delta V
  • Honeywell Plant Scape
  • Yokogawa CENTUM
  • Power Studio Deluxe

Answer: Power Studio Deluxe

Question 13 What does NC stands for?

  • New Configuration
  • Normally Close
  • Normal Classes
  • Never Closing

Answer: Normally Close

Question 14 What is nominal DC voltage given to PLC?

  • +10V
  • +24V
  • +5V
  • +12V

Answer: +5V

Question 15 In which of the following is a PLC Programming tool.

  • RS Logix 500
  • RS view 32
  • Keil u vision
  • Core Vision AVR

Answer: RS Logix 500

Question 16 Among following which one is a PLC Programming Language

  • Assembly
  • Ladder Logic
  • Java
  • HTML

Answer: Ladder Logic

Question 17 In which of the following is the SCADA Software?

  • OrCAD
  • RS View32
  • Keil u vision
  • Porteous

Answer: RS View32

Question 18 Ladder logic programming consists primarily of:

  • Virtual relay contacts and coils
  • Logic gate symbols with connecting lines
  • Function blocks with connecting lines
  • Text-based code
  • Hieroglyphics

Answer: Virtual relay contacts and coils

Question 19 Examine-on instruction in PLC language is symbolically represented by what shape?

  • -] [-
  • -( )-
  • -]/[-
  • None of these

Answer: -] [-

Question 20 The symbol -(L)- represent what instruction in the PLC language?

  • OUT output unlatch instruction.
  • OTL output latch instruction
  • Examine off instruction.
  • Output energize instruction

Answer: OTL output latch instruction

Question 21 In a PLC, the scan time refers to the amount of time in which …..

  • The technician enters the program
  • Timers and counters are indexed by
  • One “rung” of ladder logic takes to complete
  • The entire program takes to execute
  • Transmitted data communications must finish

Answer: The entire program takes to execute

Question 22 The Boolean representation of this PLC program is:

  • ABC + D
  • C + (A + B)D
  • C + D(A + B)
  • ABC + BD
  • C(AB + D)

Answer: C(AB + D)

Question 23 What is the color used for NO type switches?

  • Red
  • Green
  • non of the above

Answer: non of the above

Question 24 To reset the time for a PLC what condition must be true?

  • Reset rung of TON must be true.
  • Reset rung of TON must be false.
  • RST instruction with timer address must be true.
  • RST instruction with associated timer address must be false

Answer: RST instruction with timer address must be true.

Question 25 The below rung would represent what Boolean equation?

  • X • Y = Z
  • X + Y = Z
  • X • Y’ = Z
  • None of the above.

Answer: X • Y’ = Z

Question 26 To increase the number of inputs and outputs of the PLC, one can use expansion modules.

  • True.
  • False.
  • None of the above.

Answer: True.

Question 27 Solenoids, lamps, motors are connected to:

  • Analog output.
  • Digital output.
  • Analog input.
  • Digital input

Answer: Digital output.

Question 28 The _____ is moved toward the relay electromagnet when the relay is on.

  • Armature
  • Coil
  • NO contact
  • NC contact

Answer: Armature

Question 29 In a current sinking DC input module _____

  • The current flows out of the input field device
  • Requires that a AC sources be used with mechanical switches
  • The current flows out of the input module
  • Currents can flow in either direction at the input module

Answer: The current flows out of the input field device

Question 30 AC output field devices can interface to _____

  • AC output modules
  • Relay output modules
  • Both a and b
  • Neither a or b

Answer: Both a and b

Question 31 The difference between online and offline PLC programming is . . .

  • Whether the PLC is running or stopped
  • Whether the programming PC has internet connectivity
  • The type of programming cable used
  • Where the edited program resides
  • The type of programmer used

Answer: Where the edited program resides

Question 32 In PLC programming, a retentive function is one that:

  • Defaults to the “on” state
  • Comes last in the program
  • Defaults to the “off” state
  • Cannot be edited or deleted
  • Is not reset after a power cycle

Answer: Is not reset after a power cycle

Question 33 Normally open contacts are open when:

  • When Input is not energized
  • When the input is energized
  • When input is higher than 20 volts
  • None of these

Answer: When Input is not energized

Question 34 What is the largest integer number that a PLC counter function can reach if it uses a 16 bit register?

  • 32,768
  • 65,535
  • 65,536
  • 65,537
  • 32,767

Answer: 65,535

Question 35 An NOR function implemented in ladder logic uses:

  • Normally-closed contacts in series
  • Normally-open contacts in series
  • A single normally-closed contact
  • Normally-open contacts in parallel
  • Normally-closed contacts in parallel

Answer: Normally-closed contacts in series

Question 36 Which of the following instruction enables a jump to a subroutine?

  • JMP
  • SBR
  • RET
  • None of the above

Answer: JMP

Question 37 What are the features of SCADA?

  • Control feature using a graphical representation
  • Alarm Handling
  • Security Management
  • All of the above

Answer: All of the above

Question 38 Leading SCADA providers companies are.

  • Siemens WinCC
  • Microsoft
  • TCS
  • All of the above

Answer: Siemens WinCC

Question 39 What is Scripts in SCADA?

  • Scripts are basically a form
  • Scripts are basically a function
  • Scripts are basically a facility
  • Scripts are basically a favorite

Answer: Scripts are basically a function

Question 40 What is CIMPLICITY?

  • SCADA package
  • SCADA hardware
  • SCADA software
  • SCADA handler

Answer: SCADA package

Question 41 A good application for a timed interrupt in a PLC program would be:

  • A communications function block
  • A PID function block
  • A math function block
  • A motor start/stop rung
  • A “watchdog” timer

Answer: A PID function block

Question 42 What is the full form of RTU ?

  • Remote Terminate Unit
  • Remote Terminal Unit
  • Remote Translation Unit
  • Remote Transfer Unit

Answer: Remote Terminal Unit

Question 43 What is the full form DDE?

  • Dynamic Data Exchange
  • Data Dynamic Exchange
  • Domain Data Exchange
  • Different Data Exchange

Answer: Dynamic Data Exchange

Question 44 What is the difference between SCADA and HMI.

  • Both are same
  • HMI is not related with SCADA
  • HMI can be a part of SCADA but SCADA can’t be a part of HMI.
  • SCADA is a part of HMI

Answer: HMI can be a part of SCADA but SCADA can’t be a part of HMI.

Question 45 What are the differences between PLC and SCADA?

  • PLC is a hardware part while SCADA is a software part.
  • PLC is a  software  part while SCADA is a hardware part.
  • Both are hardware unit
  • Both are software

Answer: PLC is a hardware part while SCADA is a software part.

Question 46 A PLC consists of

  • Processor Unit
  • Program Memory
  • Input/output Section
  • Display Device
  • All of the above

Answer: All of the above

Question 47 An OR function implemented in ladder logic uses:

  • Normally-closed contacts in series
  • Normally-open contacts in series
  • A single normally-closed contact
  • Normally-open contacts in parallel
  • Normally-closed contacts in parallel

Answer: Normally-open contacts in parallel

Question 48 What is the full form of NEMA ?

National Electronics Manufacturing Association
National Electrical Manufacturing Association 
National Electrotechnical Manufacturing Association 
National Electromechanical Manufacturing Association 

Answer: National Electrical Manufacturing Association 

Question 49 Which of the following is not element of SCADA:

  • SCADA Communication
  • Mono Terminal Units
  • PLCs
  • RTUs

Answer: Mono Terminal Units

Question 50 Identify the problem in this motor control PLC program:

  • Coil
  • Start contact
  • Seal-in contact
  • Stop contact
  • Power source

Answer: Seal-in contact


#2 PLC MCQ

Top 10 Multiple choice questions on Programmable logic controller


Question 1: The PLC was invented by.

  • Bill Gates
  • Dick Morley
  • Bill Landis
  • Tod Cunningham

Answer: Dick Morley

Question 2: The first company to build PLCs was.

  • General Motors
  • Allen Bradley
  • Square D
  • Modicon

Answer: Modicon

Question 3: Which part of plc monitors the inputs and makes decisions in a PLC.

  • Sensor
  • CPU
  • Input Module
  • Output Module

Answer: CPU

Question 4: One of the following is an input device.

  • Motor
  • Light
  • Valve
  • Sensor

Answer: Sensor

Question 5: Which one of the following is not a PLC manufacturer.

  • Siemens
  • Mitsubishi
  • Microsoft
  • ABB

Answer: Microsoft

Question 6: Solenoids, lamps, motors are connected to:

  • Analog output
  • Digital output
  • Analog input
  • Digital input

Answer: Digital output

Question 7: In a PLC “I” is used for output and “Q” is used for input.

  • True
  • False
  • None of the above

Answer: False

Question 8: To increase the number of inputs and outputs of the PLC, one can use expansion modules.

  • True
  • False
  • None of the above

Answer: True

Question 9: An example of discrete (digital) control is:

  • Varying the volume of a music system
  • Turning a lamp ON or OFF
  • Varying the brightness of a lamp
  • Controlling the speed of a fan

Answer: Turning a lamp ON or OFF

Question 10: Which of the following statements is NOT correct?

  • The status of each input can be checked from one location and outputs can be forced on and off.
  • All symbols in the RLL represent actual components and contacts present in the control system.
  • PLCs are not as reliable as electromechanical relays in RLL.
  • Input (-| |-) and output (- ( ) -) instruction symbols in the ladder logic represent only data values stored in PLC memory.

Answer: PLCs are not as reliable as electromechanical relays in RLL.

#4 PLC MCQ

Programmable Logic controller

Multiple choice questions

Question 1: The type of memory which is fast and temporarily stores the data which are immediately required for use is called as______.

a. HDD
b. ROM
c. RAM
d. SSD

Answer: RAM

Question 2: What is the largest integer number that a PLC counter function can reach if it uses a 16 bit register?

a. 32,768
b. 65,535
c. 65,536
d. 65,537
e. 32,767

Answer: 65,535

Question 3: How is the speed of operation of conventional relay system as compared to digital controllers?

a. Very slow
b. Very fast
c. Same
d. Almost similar

Answer: Very slow

Question 4: The PLC is used in _______.

a. Machine tools
b. Automated assembly equipment
c. Moulding and extrusion machines
d. All of the above

Answer: All of the above

Question 5: PLC can be ___________ in plant to change the sequence of operation.

a. only programmed
b. only reprogrammed
c. programmed and reprogrammed
d. able to give a set point

Answer: programmed and reprogrammed

Question 6: __________ of PLCs can be done in very little time.

a. Programming
b. Installation
c. Commissioning
d. All of the above

Answer: All of the above

Question 7: How is the noise immunity of PLCs to electrical noises as compared to that of conventional relay controllers?

a. poor
b. excellent
c. as good as noise immunity of conventional relay controllers
d. unpredictable

Answer: Poor

Question 8: The most popular language for PLCs is:

a. Ladder diagram
b. C++
c. OOP+
d. VHDL

Answer: Ladder diagram

Question 9: An AND function implemented in ladder logic uses:

a. Normally-closed contacts in series
b. Normally-open contacts in series
c. A single normally-closed contact
d. Normally-open contacts in parallel
e. Normally-closed contacts in parallel

Answer: Normally-open contact in series

Question 10: The PLC Can be categorized according to the

a. Power rating of the I/O module
b. Cost of the I/O module
c. Current rating of the I/O module
d. Number of I/O point

Answer: Number of I/O point

Top 10 PLC MCQ questions asked in previous year paper

Programmable Logic controller Multiple Choice Question

Top 10 PLC Programmable logic controller questions asked in various competitive exam. Please give this exam. This is free mock test and check your score.

First give this exam. If your answer is wrong then check below video for detail description of question

[ays_quiz id=”7″]

Series#1 ( Top 10 Questions )

Question 1 The acronym PLC stands for:

  1. Pressure Load Control
  2. Programmable Logic Controller
  3. Pneumatic Logic Capstan
  4. PID Loop Controller
  5. Pressure Loss Chamber

Answer: Programmable Logic Controller

Question 2 Ladder logic programming consists primarily of:

  1. Virtual relay contacts and coils
  2. Logic gate symbols with connecting lines
  3. Function blocks with connecting lines
  4. Text-based code
  5. Hieroglyphics

Answer: Virtual relay contacts and coils

Question 3 In a PLC, the scan time refers to the amount of time in which …..

  1. The technician enters the program
  2. Timers and counters are indexed by
  3. One “rung” of ladder logic takes to complete
  4. The entire program takes to execute
  5. Transmitted data communications must finish

Answer: The entire program takes to execute

Question 4 Identify the problem in this motor control PLC program:

  1. Coil
  2. Start contact
  3. Seal-in contact
  4. Stop contact
  5. Power source

Answer: Seal-in contact

Question 5 The Boolean representation of this PLC program is:

  1. ABC + D
  2. C + (A + B)D
  3. C + D(A + B)
  4. ABC + BD
  5. C(AB + D)

Answer: C(AB + D)

Question 6 The difference between online and offline PLC programming is . . .

  1. Whether the PLC is running or stopped
  2. Whether the programming PC has internet connectivity
  3. The type of programming cable used
  4. Where the edited program resides
  5. The type of programmer used

Answer: Where the edited program resides

Question 7 In PLC programming, a retentive function is one that:

  1. Defaults to the “on” state
  2. Comes last in the program
  3. Defaults to the “off” state
  4. Cannot be edited or deleted
  5. Is not reset after a power cycle

Answer: Is not reset after a power cycle

Question 8 Normally open contacts are open when:

  1. When Input is not energized
  2. When the input is energized
  3. When input is higher than 20 volts
  4. None of these

Answer: When Input is not energized

Question 9 An OR function implemented in ladder logic uses:

  1. Normally-closed contacts in series
  2. Normally-open contacts in series
  3. A single normally-closed contact
  4. Normally-open contacts in parallel
  5. Normally-closed contacts in parallel

Answer: Normally-open contacts in parallel

Question 10 A good application for a timed interrupt in a PLC program would be:

  1. A communications function block
  2. A PID function block
  3. A math function block
  4. A motor start/stop rung
  5. A “watchdog” timer

Answer: A PID function block

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FAQ’s

1. What is PLC ?

PLC stand for “Programmable Logic Controller”. It is a general purpose computer modified specifically to perform control task . It is a hardware device having microprocessor based control system. It is used in industrial automation.

2. What do you mean by PLC scan time?

PLC Scan Time is the time taken by the PLC to read the inputs, solve the Logic, and update the output is called a PLC Scan Time. This time is measured in millisecond .

3. Which is the most popular language in plc programming ?

The most popular language in plc programming is Ladder Logic Diagram.

4. What are the applications of PLC ?

PLC is used in industrial automation. These controllers can automate a specific process, machine function, or even an entire production line.

5. What are components of PLC system ?

There are major 6 components of PLC:
•Processor (CPU)
•Rack/Mounting
•Input Module
•Output Module
•Power Supply
•Programming Device/Unit

6. What is ladder diagram ?

Ladder diagram is the most popular programming language used in Plc programming. Ladder diagrams expresses a program as a series of “coils” and “contacts”, simulating the operation of electromechanical relays.
The advantage of ladder diagram is the familiarity many electricians have with the simple operation of relays.


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