This blog post provides a detailed overview of the recent NAIR Assistant Electrical Engineer exam, including key concepts, important questions, and explanations related to electrical engineering principles relevant to the railway sector.
Hello friends, good morning! I hope you are all doing well and continuing your preparations. Today’s video is quite important as we will discuss the recent NAIR Assistant Electrical Engineer exam conducted by NAIR CBT. We will review the paper in detail, providing explanations for each question.
The exam for the Assistant Electrical Engineer position is crucial for aspiring candidates. It tests knowledge in various electrical engineering concepts that are essential for working in the railway sector.
Question: Which parameter of power supply determines the synchronous speed of an induction motor?
Answer: The correct answer is Frequency. The synchronous speed (Ns) of an induction motor is given by the formula:
Ns = 120 * f / P
where f is the supply frequency and P is the number of poles. Induction motors always run at a speed less than synchronous speed due to full load slip.
Question: What is an instrument transformer?
Answer: The correct answer is Potential and Current Transformer. Instrument transformers are used to measure electrical quantities like voltage, current, power, energy, frequency, and power factor.
Question: In a star-connected three-phase system, what is the relationship between line voltage and phase voltage?
Answer: The correct answer is Line Voltage = √3 * Phase Voltage. In a star connection, the line voltage leads the phase voltage by 30 degrees.
Question: Which type of braking is used to save energy during braking?
Answer: The correct answer is Regenerative Braking. In regenerative braking, the electric motor works like a generator, feeding power back to the supply system.
Question: If two 80-ohm resistors are connected in parallel, what is the equivalent resistance?
Answer: The correct answer is 40 ohms. For resistors in parallel, the formula is:
1/R = 1/R1 + 1/R2.
Question: What is the full form of BEE?
Answer: The correct answer is Bureau of Energy Efficiency. It is an agency of the Government of India under the Ministry of Power, established in March 2002.
Question: Which relay is a gas-operated relay in a transformer?
Answer: The correct answer is Buchholz Relay. It is used for the protection of transformers against internal faults.
Question: In domestic wiring, what provides protection from electrical shock?
Answer: The correct answer is RCCB (Residual Current Circuit Breaker). It protects against electrical shocks in domestic wiring.
Question: What is the full form of APFC in electrical substations?
Answer: The correct answer is Automatic Power Factor Controller.
Question: Which statements are correct regarding MCB and Isolator?
Answer: The correct answer is All of the given options are correct. MCB is an on-load device while the isolator is an off-load device.
Question: The primary winding of which transformer should never be energized when the winding is open-circuited?
Answer: The correct answer is Current Transformer. The secondary winding should always be short-circuited to avoid core saturation.
Question: Who is the electrical inspector to the Government of India for zonal railways?
Answer: The correct answer is Principal Chief Electrical Engineer of Zonal Railways (PCDE).
Question: A 25-liter capacity geyser rated at 1500 watts is switched on for 2 hours daily for 30 days. What is the electricity consumption?
Answer: The correct answer is 90 units. The calculation is done by multiplying the wattage by hours and days, then dividing by 1000.
Question: How many diodes are required in a single-phase full-wave bridge rectifier?
Answer: The correct answer is 4 diodes.
Question: What does a chopper convert?
Answer: The correct answer is Fixed DC supply to Variable DC supply.
Question: Which type of locomotive uses the Hitachi HS 15250 type traction motor?
Answer: The correct answer is WAP-4 and WAG-7.
Question: What does Co-Co bogie mean in electrical locomotives?
Answer: The correct answer is Three driving wheel sets.
Question: In locomotives, sand is used to avoid which issue?
Answer: The correct answer is Wheel slipping.
This comprehensive review of the NAIR Assistant Electrical Engineer exam highlights the essential concepts and questions that candidates should focus on. Understanding these principles is crucial for success in the railway sector and for aspiring electrical engineers. Keep studying and best of luck with your preparations!
