Preparing for the Junior Engineer (Electrical / Electronics) test requires a strong command of core engineering concepts as well as regular practice of exam-level multiple-choice questions(MCQS). The following MCQs are carefully prepared to reflect the pattern, difficulty level, and syllabus coverage commonly seen in Junior Engineer examinations, including topics such as electrical machines, power systems, basic electronics, measurements, and protection. All questions are original and uniquely created for practice purposes, making them suitable for self-assessment as well as competitive exam preparation. This practice set will assist candidates strengthen conceptual understanding, enhance problem-solving speed, and gain confidence for the actual recruitment test.
Practice MCQs
1. In a DC shunt motor, the speed mainly depends on:
A) Armature current
B) Field flux and supply voltage
C) Load torque only
D) Armature resistance only
Correct Answer: B
Explanation:
In a DC shunt motor, the field winding is connected in parallel with the supply, so the field flux remains nearly constant. Therefore, speed mainly varies with applied voltage and flux.
2. Which component is primarily responsible for reducing voltage fluctuations in a power supply?
A) Rectifier
B) Transformer
C) Voltage regulator
D) Fuse
Correct Answer: C
Explanation:
A voltage regulator maintains a constant output voltage even when the input voltage or load changes, ensuring stable operation of electronic circuits.
3. The unit of electrical resistivity is:
A) Ohm
B) Ohm-meter
C) Siemens
D) Meter
Correct Answer: B
Explanation:
Resistivity is a material property that shows how strongly a material opposes current flow. Its SI unit is ohm-meter (Ω·m).
4. In a three-phase star-connected system, the line voltage is equal to:
A) Phase voltage
B) √3 × phase voltage
C) Phase voltage / √3
D) 3 × phase voltage
Correct Answer: B
Explanation:
In a three-phase star (Y) system, line voltage is higher than phase voltage due to the phase difference between voltages.
Transformer (MCQS)
5. Which loss in a transformer remains constant regardless of load?
A) Copper loss
B) Leakage loss
C) Core (iron) loss
D) Stray loss
Correct Answer: C
Explanation:
Core (iron) loss depends on supply voltage and frequency, not on load current, so it remains almost constant at all loads.
6. The function of a circuit breaker in a power system is to:
A) Measure current
B) Amplify voltage
C) Interrupt fault current
D) Improve power factor
Correct Answer: C
Explanation:
A circuit breaker automatically disconnects the circuit when a fault such as short circuit or overload occurs, protecting equipment and personnel.
7. Which semiconductor device is commonly used for controlled rectification?
A) Zener diode
B) SCR
C) LED
D) Photodiode
Correct Answer: B
Explanation:
An SCR allows control over when current starts flowing, making it suitable for controlled rectifier and power control applications.
8. The power factor of a purely resistive AC circuit is:
A) Zero
B) 0.5
C) Unity
D) Lagging
Correct Answer: C
Explanation:
In a purely resistive AC circuit, current and voltage are in phase, so the power factor is 1 (unity).
9. Skin effect in conductors increases with:
A) Decrease in frequency
B) Increase in frequency
C) Increase in voltage
D) Decrease in temperature
Correct Answer: B
Explanation:
At higher frequencies, current tends to flow near the surface of the conductor, increasing effective resistance. This phenomenon is called skin effect.
Instruments (MCQS)
10. Which instrument is suitable for measuring AC and DC current?
A) PMMC instrument
B) Moving iron instrument
C) Electrostatic instrument
D) Induction type instrument
Correct Answer: B
Explanation:
Moving iron instruments work on magnetic effect of current, which is independent of current direction, so they can measure both AC and DC.
11. The efficiency of an ideal transformer is:
A) Less than 90%
B) Equal to 100%
C) Greater than 100%
D) Zero
Correct Answer: B
Explanation:
An ideal transformer has no losses (no copper or core losses), so all input power is transferred to output. So equal to 100%
12. In an R-L circuit, current lags voltage due to:
A) Resistance
B) Inductance
C) Capacitance
D) Conductance
Correct Answer: B
Explanation:
Inductors oppose change in current, causing the current to lag behind the voltage in an R-L circuit.
13. Which type of relay operates on the principle of electromagnetic attraction?
A) Thermal relay
B) Distance relay
C) Induction relay
D) Overcurrent relay
Correct Answer: D
Explanation:
Overcurrent relays operate when current exceeds a preset value, using electromagnetic force to activate the relay mechanism.
14. A step-up transformer increases:
A) Power
B) Frequency
C) Voltage
D) Efficiency
Correct Answer: C
Explanation:
A step-up transformer has more turns on the secondary side, which increases output voltage while reducing current.
15. The main purpose of earthing in electrical systems is to:
A) Increase current
B) Improve efficiency
C) Protect equipment and personnel
D) Reduce voltage
Correct Answer: C
Explanation:
Earthing provides a low-resistance path for fault current, preventing electric shock and damage to electrical equipment.
16. Which parameter defines the opposition offered by an inductor to AC?
A) Resistance
B) Inductive reactance
C) Capacitance
D) Conductance
Correct Answer: B
Explanation:
Inductive reactance is the opposition offered by an inductor to alternating current and increases with frequency.
Transistor (MCQS)
17. The collector region of a BJT is moderately doped to:
A) Reduce noise
B) Handle higher voltage
C) Increase base current
D) Reduce gain
Correct Answer: B
Explanation:
The collector region must withstand high reverse voltage, so it is designed to be moderately doped and physically larger.
18. The primary function of a condenser in a thermal power plant is to:
A) Increase steam pressure
B) Convert exhaust steam into water
C) Preheat boiler feedwater
D) Remove dissolved gases
Correct Answer: B
Explanation:
In a thermal power plant, the condenser cools exhaust steam from the turbine and converts it back into water for reuse.
19. Which quantity is measured in kilovolt-ampere (kVA)?
A) Active power
B) Reactive power
C) Apparent power
D) Mechanical power
Correct Answer: C
Explanation:
Apparent power is the product of RMS voltage and current in an AC circuit and is measured in kilovolt-ampere (kVA).
20. In a PN junction diode, current flows mainly due to:
A) Minority carriers
B) Majority carriers
C) Ions
D) Free electrons only
Correct Answer: B
Explanation:
In a PN junction diode, conduction mainly occurs due to majority carriers when the diode is forward biased.
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Conclusion
Practicing well-structured Multiple-choice questions (MCQs) is one of the most effective ways to prepare for the Junior Engineer (Electrical / Electronics) examination. This MCQ set has been designed to align with the exam syllabus and conceptual requirements, while remaining completely original and unique. Candidates are encouraged to review each question carefully, understand the underlying concepts, and identify weak areas for further study. Each MCQ is explain with very simple way. Regular practice of such exam-oriented questions will significantly improve accuracy, time management, and overall performance in competitive engineering tests.