Industrial Electronics Questions Answers: Introduction
Industrial electronics is the backbone of modern industries, covering everything from power supplies and control circuits to automation and motor drives.
Whether you are a diploma student, ITI trainee, engineering learner, or preparing for competitive or interview exams, a strong grip on basic industrial electronics is important.
To help you revise quickly and effectively, this article presents 80 Industrial Electronics Objective Questions and Answers with one-line explanations, carefully designed to improve your concepts, boost exam confidence, and strengthen your technical foundation in a short time.
Industrial Electronics Questions Answers
Q1. What is the main function of a diode in an electronic circuit?
a) Amplification
b) Rectification
c) Oscillation
d) Modulation
Correct Answer: b
Explanation: A diode allows current to flow in only one direction and is mainly used for rectification.
Q2. Which device is commonly used for amplification in electronics?
a) Diode
b) Transistor
c) Relay
d) Fuse
Correct Answer: b
Explanation: A transistor amplifies weak electrical signals into stronger signals.
Q3. What is the primary use of a Zener diode?
a) Switching
b) Voltage regulation
c) Rectification
d) Amplification
Correct Answer: b
Explanation: A Zener diode maintains a constant output voltage during fluctuations.
Q4. Which semiconductor material is most widely used in electronics?
a) Copper
b) Germanium
c) Silicon
d) Iron
Correct Answer: c
Explanation: Silicon is widely used due to its stability and low cost.
Q5. What is the unit of electrical resistance?
a) Volt
b) Ampere
c) Ohm
d) Watt
Correct Answer: c
Explanation: Resistance is measured in ohms.
Q6. Which component stores electrical energy in the form of an electric field?
a) Resistor
b) Capacitor
c) Inductor
d) Transformer
Correct Answer: b
Explanation: A capacitor stores energy between its plates as an electric field.
Q7. What is the unit of capacitance?
a) Henry
b) Coulomb
c) Farad
d) Tesla
Correct Answer: c
Explanation: Capacitance is measured in farads.
Q8. Which component stores energy in the form of a magnetic field?
a) Capacitor
b) Resistor
c) Inductor
d) Diode
Correct Answer: c
Explanation: An inductor stores energy in a magnetic field.
Q9. On which principle does a transformer work?
a) Electrostatics
b) Mutual induction
c) Photoelectric effect
d) Piezoelectric effect
Correct Answer: b
Explanation: A transformer transfers power through mutual induction between coils.
Q10. Which device is used to convert AC into DC?
a) Inverter
b) Rectifier
c) Oscillator
d) Regulator
Correct Answer: b
Explanation: A rectifier converts alternating current into direct current.
Q11. How many diodes are used in a full-wave rectifier with center tap?
a) One
b) Two
c) Three
d) Four
Correct Answer: b
Explanation: Two diodes are used to rectify both halves of the AC waveform.
Q12. Which rectifier produces the minimum ripple output?
a) Half-wave rectifier
b) Full-wave rectifier
c) Bridge rectifier
d) Clipper circuit
Correct Answer: c
Explanation: A bridge rectifier provides smoother DC with less ripple.
Q13. Which filter is commonly used in DC power supplies to reduce ripple?
a) Notch filter
b) RC filter
c) Band-stop filter
d) High-pass filter
Correct Answer: b
Explanation: An RC filter smoothens the DC output by reducing ripple.
Q14. What is the unit of inductance?
a) Weber
b) Henry
c) Tesla
d) Farad
Correct Answer: b
Explanation: Inductance is measured in henry.
Q15. Which device is used to control large power using a small signal?
a) Diode
b) Transistor
c) Capacitor
d) Fuse
Correct Answer: b
Explanation: A transistor controls high current using a small input signal.
Q16. What are the three terminals of a bipolar junction transistor (BJT)?
a) Drain, Gate, Source
b) Anode, Cathode, Gate
c) Emitter, Base, Collector
d) Primary, Secondary, Core
Correct Answer: c
Explanation: A BJT consists of emitter, base, and collector terminals.
Q17. What does MOSFET stand for?
a) Metal Oxide Semiconductor Field Effect Transistor
b) Micro Oxide Silicon Field Transistor
c) Metal Open Source Field Effect Transistor
d) Magnetic Oxide Semiconductor Transistor
Correct Answer: a
Explanation: A MOSFET is a voltage-controlled semiconductor switching device.
Q18. Which device is most commonly used in SMPS circuits?
a) SCR
b) MOSFET
c) Relay
d) Diode
Correct Answer: b
Explanation: MOSFETs are used for high-speed switching in SMPS.
Q19. Which component protects a circuit from overcurrent?
a) Inductor
b) Capacitor
c) Fuse
d) Transformer
Correct Answer: c
Explanation: A fuse disconnects the circuit during excess current flow.
Q20. What is the function of a relay in an electronic circuit?
a) Power source
b) Mechanical sensor
c) Electrically operated switch
d) Voltage regulator
Correct Answer: c
Explanation: A relay switches high-power circuits using a low-power control signal.
Q21. What is the full form of SCR?
a) Silicon Controlled Rectifier
b) Solid Current Regulator
c) Semiconductor Control Resistor
d) Single Current Rectifier
Correct Answer: a
Explanation: SCR is a thyristor used for controlled rectification of power.
Q22. What is the main application of an SCR?
a) Signal amplification
b) Power control
c) Voltage measurement
d) Frequency generation
Correct Answer: b
Explanation: SCR is mainly used to control high power in industrial circuits.
Q23. Which device is used for AC power control in both directions?
a) Diode
b) SCR
c) TRIAC
d) Transistor
Correct Answer: c
Explanation: A TRIAC can conduct current in both directions of AC.
Q24. What is the function of the gate terminal in an SCR?
a) To supply power
b) To trigger the device
c) To provide feedback
d) To regulate voltage
Correct Answer: b
Explanation: The gate is used to turn ON the SCR.
Q25. Which device is used to provide electrical isolation between two circuits?
a) Transformer
b) Optocoupler
c) Resistor
d) Capacitor
Correct Answer: b
Explanation: An optocoupler provides isolation using light transmission.
Q26. Which IC is commonly used as a 5 V voltage regulator?
a) 741
b) 555
c) 7805
d) 4017
Correct Answer: c
Explanation: IC 7805 provides a fixed regulated 5 V output.
Q27. What is the output voltage of IC 7812?
a) 5 V
b) 9 V
c) 12 V
d) 24 V
Correct Answer: c
Explanation: IC 7812 is a fixed 12 V voltage regulator.
Q28. Which IC is most commonly used as a timer?
a) 741
b) 7805
c) 555
d) 4017
Correct Answer: c
Explanation: IC 555 is widely used for timing and pulse generation.
Q29. What does an inverter convert?
a) AC to DC
b) DC to AC
c) AC to AC
d) DC to DC
Correct Answer: b
Explanation: An inverter converts DC power into AC power.
Q30. Which instrument is used to measure voltage digitally?
a) Ammeter
b) Galvanometer
c) Multimeter
d) Energy meter
Correct Answer: c
Explanation: A digital multimeter measures voltage, current, and resistance.
Q31. What does PCB stand for?
a) Power Control Board
b) Printed Circuit Board
c) Process Control Board
d) Power Circuit Box
Correct Answer: b
Explanation: A PCB mechanically supports and electrically connects components.
Q32. Which tool is used for soldering electronic components?
a) Welding torch
b) Soldering iron
c) Heat gun
d) Hammer
Correct Answer: b
Explanation: A soldering iron is used to join electronic components using solder.
Q33. What is the main purpose of a heat sink?
a) To increase temperature
b) To store charge
c) To dissipate heat
d) To amplify signal
Correct Answer: c
Explanation: A heat sink removes excess heat from electronic components.
Q34. Which device protects circuits from voltage surges?
a) Fuse
b) Varistor
c) Inductor
d) Rectifier
Correct Answer: b
Explanation: A varistor absorbs high-voltage surges to protect circuits.
Q35. What is the standard AC supply frequency in India?
a) 25 Hz
b) 60 Hz
c) 50 Hz
d) 100 Hz
Correct Answer: c
Explanation: India follows a standard AC supply frequency of 50 Hz.
Q36. Which instrument is used to measure resistance?
a) Voltmeter
b) Ammeter
c) Ohmmeter
d) Wattmeter
Correct Answer: c
Explanation: An ohmmeter directly measures electrical resistance.
Q37. Which logic gate gives a HIGH output only when both inputs are HIGH?
a) OR
b) AND
c) NOT
d) NOR
Correct Answer: b
Explanation: AND gate outputs HIGH only when all inputs are HIGH.
Q38. Which logic gate is called a universal gate?
a) AND
b) OR
c) NAND
d) XOR
Correct Answer: c
Explanation: NAND gate can be used to implement any logic function.
Q39. What is the full form of UPS?
a) Universal Power Supply
b) Uninterrupted Power System
c) Uninterruptible Power Supply
d) Unified Power Supply
Correct Answer: c
Explanation: A UPS provides backup power during mains failure.
Q40. Which semiconductor device is sensitive to light?
a) LED
b) Photodiode
c) Zener diode
d) SCR
Correct Answer: b
Explanation: A photodiode generates current based on incident light.
Q41. What does LED stand for?
a) Low Energy Diode
b) Light Emitting Diode
c) Light Energy Device
d) Linear Emitting Diode
Correct Answer: b
Explanation: An LED emits light when it is forward biased.
Q42. Which device produces light when current flows through it?
a) Diode
b) Zener diode
c) LED
d) SCR
Correct Answer: c
Explanation: An LED converts electrical energy into light energy.
Q43. Which parameter is commonly controlled using TRIAC in industries?
a) Temperature
b) Pressure
c) Speed
d) Level
Correct Answer: c
Explanation: TRIAC is widely used for AC motor speed control.
Q44. What does PWM stand for?
a) Pulse Width Modulation
b) Power Wave Modulation
c) Phase Width Measurement
d) Power Wave Measurement
Correct Answer: a
Explanation: PWM controls power by varying the width of pulses.
Q45. What is the main application of PWM?
a) Voltage measurement
b) Speed control
c) Frequency measurement
d) Signal filtering
Correct Answer: b
Explanation: PWM is mainly used for motor speed and power control.
Q46. Which IC is commonly used as an operational amplifier?
a) 555
b) 7805
c) 741
d) 4017
Correct Answer: c
Explanation: IC 741 is a widely used operational amplifier.
Q47. What is the full form of SMPS?
a) Simple Mode Power Supply
b) Switched Mode Power Supply
c) Standard Mode Power Supply
d) Static Mode Power Supply
Correct Answer: b
Explanation: SMPS converts electrical power efficiently using high-frequency switching.
Q48. Which component is used to limit current in a circuit?
a) Capacitor
b) Inductor
c) Resistor
d) Diode
Correct Answer: c
Explanation: A resistor restricts the flow of current in a circuit.
Q49. Which quantity is measured in watts?
a) Voltage
b) Current
c) Power
d) Resistance
Correct Answer: c
Explanation: Electrical power is measured in watts.
Q50. Which type of memory stores data temporarily?
a) ROM
b) Hard disk
c) SSD
d) RAM
Correct Answer: d
Explanation: RAM stores data temporarily while the system is operating.
Q51. What does PLC stand for?
a) Process Logic Controller
b) Programmable Logic Controller
c) Power Line Controller
d) Programmable Load Controller
Correct Answer: b
Explanation: PLC is a digital controller used for industrial automation.
Q52. What is the main use of a PLC?
a) Power generation
b) Industrial automation
c) Signal amplification
d) Voltage measurement
Correct Answer: b
Explanation: PLCs are used to automate industrial processes.
Q53. Which PLC programming language is most commonly used?
a) Python
b) C++
c) Ladder Logic
d) Java
Correct Answer: c
Explanation: Ladder Logic is widely used because it resembles electrical wiring diagrams.
Q54. Which sensor converts temperature into an electrical signal?
a) Pressure sensor
b) Proximity sensor
c) Temperature sensor
d) Flow sensor
Correct Answer: c
Explanation: A temperature sensor changes temperature into an electrical signal.
Q55. On which principle does a thermocouple work?
a) Ohm’s Law
b) Faraday’s Law
c) Seebeck effect
d) Lenz’s Law
Correct Answer: c
Explanation: Thermocouples work on the Seebeck effect of voltage generation due to temperature difference.
Q56. Which instrument is used to measure electric current?
a) Voltmeter
b) Wattmeter
c) Ammeter
d) Ohmmeter
Correct Answer: c
Explanation: An ammeter measures the flow of electric current.
Q57. Which motor operates on AC supply?
a) DC shunt motor
b) Induction motor
c) Stepper motor
d) Servo motor
Correct Answer: b
Explanation: An induction motor runs on alternating current.
Q58. Which motor is most widely used in industrial applications?
a) DC motor
b) Stepper motor
c) Induction motor
d) Servo motor
Correct Answer: c
Explanation: Induction motors are rugged, low-cost, and widely used in industries.
Q59. Which instrument is used to measure electrical power?
a) Voltmeter
b) Ammeter
c) Wattmeter
d) Ohmmeter
Correct Answer: c
Explanation: A wattmeter measures electrical power consumed by a load.
Q60. Which device is used to protect equipment from lightning and surge voltage?
a) Transformer
b) Surge protector
c) Capacitor
d) Fuse
Correct Answer: b
Explanation: A surge protector diverts excess voltage safely to the ground.
Q61. Which material is commonly used for PCB tracks?
a) Aluminium
b) Copper
c) Iron
d) Tin
Correct Answer: b
Explanation: Copper is used due to its low resistance and excellent conductivity.
Q62. Which instrument is used to measure frequency?
a) Multimeter
b) Wattmeter
c) Frequency meter
d) Tachometer
Correct Answer: c
Explanation: A frequency meter directly measures the frequency of an electrical signal.
Q63. Which device converts mechanical energy into electrical energy?
a) Motor
b) Generator
c) Transformer
d) Battery
Correct Answer: b
Explanation: A generator converts mechanical energy into electrical energy.
Q64. Which type of supply is required for most electronic circuits?
a) AC supply
b) DC supply
c) Pulsed supply
d) High-voltage supply
Correct Answer: b
Explanation: Most electronic circuits operate on stable DC supply.
Q65. Which battery is most commonly used in UPS systems?
a) Dry cell
b) Lead-acid battery
c) Lithium coin cell
d) Nickel-cadmium battery
Correct Answer: b
Explanation: Lead-acid batteries are widely used in UPS due to high current capability.
Q66. Which device provides electrical isolation between high and low voltage circuits?
a) Capacitor
b) Transformer
c) Resistor
d) Diode
Correct Answer: b
Explanation: A transformer isolates two circuits using magnetic coupling.
Q67. Which law defines the relationship between voltage, current, and resistance?
a) Faraday’s Law
b) Kirchhoff’s Law
c) Ohm’s Law
d) Coulomb’s Law
Correct Answer: c
Explanation: Ohm’s Law states that voltage is directly proportional to current.
Q68. Which combination converts AC into well-regulated DC?
a) Inverter + filter
b) Rectifier + filter + regulator
c) Oscillator + amplifier
d) Transformer only
Correct Answer: b
Explanation: A rectifier converts AC to DC, filter smooths it, and regulator stabilizes it.
Q69. Which device is used to detect phase sequence and phase failure?
a) Contactor
b) Transformer
c) Phase sequence relay
d) Fuse
Correct Answer: c
Explanation: Phase sequence relays protect motors from incorrect phase conditions.
Q70. Which device is used to amplify weak electrical signals?
a) Capacitor
b) Transformer
c) Amplifier
d) Rectifier
Correct Answer: c
Explanation: An amplifier increases the strength of weak input signals.
Q71. Which IC is used as a decade counter?
a) 741
b) 7805
c) 4017
d) 555
Correct Answer: c
Explanation: IC 4017 provides ten decoded output counts.
Q72. Which device generates clock pulses in electronic circuits?
a) Oscillator
b) Rectifier
c) Transformer
d) Regulator
Correct Answer: a
Explanation: An oscillator produces continuous periodic signals.
Q73. Which quantity is measured in Hertz (Hz)?
a) Voltage
b) Current
c) Frequency
d) Resistance
Correct Answer: c
Explanation: Hertz is the unit of frequency.
Q74. Which device is used for contactless current measurement?
a) Ammeter
b) Hall Effect sensor
c) Voltmeter
d) Ohmmeter
Correct Answer: b
Explanation: Hall Effect sensors measure current without direct electrical contact.
Q75. Which semiconductor device has three layers and three terminals?
a) Diode
b) Transistor
c) Capacitor
d) Resistor
Correct Answer: b
Explanation: A transistor consists of three semiconductor layers and three terminals.
Q76. Which instrument is commonly used to test continuity?
a) Oscilloscope
b) Multimeter
c) Signal generator
d) Power supply
Correct Answer: b
Explanation: A multimeter checks continuity using a low-resistance test.
Q77. Which type of capacitor is polarized?
a) Ceramic capacitor
b) Paper capacitor
c) Electrolytic capacitor
d) Mica capacitor
Correct Answer: c
Explanation: Electrolytic capacitors must be connected with correct polarity.
Q78. Which device converts digital signals into analog signals?
a) ADC
b) DAC
c) PLC
d) SMPS
Correct Answer: b
Explanation: DAC converts digital data into equivalent analog output.
Q79. Which device converts analog signals into digital signals?
a) DAC
b) Transformer
c) ADC
d) Relay
Correct Answer: c
Explanation: ADC converts continuous analog signals into digital form.
Q80. Which device is used for backup power supply in industries?
a) Stabilizer
b) UPS
c) Transformer
d) Rectifier
Correct Answer: b
Explanation: A UPS provides uninterrupted power during mains failure.
This set of 80 Industrial Electronics objective questions and answers covers all the key fundamentals required for students, technicians, and beginners in the field of industrial electronics.
From basic components like diodes, transistors, and rectifiers to advanced topics like PLC, SMPS, PWM, and industrial protection devices, this question bank helps strengthen core concepts in a simple and exam-oriented manner.
Regular practice of these MCQs will not only improve technical understanding but also boost confidence for interviews, competitive exams, and practical industrial applications.
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