RRB JOBS QUESTION BANK : JUNIOR ENGINEER (NON-AC) WRITE SHORT NOTES

 

1) Why earthing is necessary for any electrical equipments, domestic installation & service building etc?

Ans: To drain away any leakage of currents due to poor insulation and to save human life from dangerous shock and also to avoid burnt of electrical equipment.

 

2) What are Different type of earth conductor and sizes?

Ans: a) Copper plate electrode Minimum 60 cm X 60 cm X 3.15 mm

b) Galvanized iron & steel plate electrode 60 cm X 60 cm X 6.3 mm

c) G.I. Pipe electrode internal diameter 50 mm and length 2.5 Mtrs

 

3) Action to be taken if the resistance to earth of earth electrode is high?

Ans: Earth resistance depends upon soil conductivity. To reduce earth resistance dig around the earth electrode, clean all the rust around earth plate or pipe. Sprinkle the common salt dissolved water in the pit and pack it up with powdered coke & salt. If it is not possible provide additional earths and connects all the earth points in parallel by solid jumper connections.

 

4) What happens if electrical connection or electrical joint is loose?

Ans: due to loose connection at joints resistance at that point will increase thereby the I²R loses are more and develops heat. The total wiring may burn.

 

5) Explain how to use Fire extinguisher practically?

Ans: a) Pull the pin at the top of the extinguisher.

b) Aim the nozzle towards the base of the fire.

c) Stand approximately 8 feet away from the fire and squeeze the handle to discharge the extinguisher.

d) Sweep the nozzle back and forth at the base of the fire.

 

6) What are the precautions to be taken before starting work on electrical installations?

Ans: Before starting any electrical works on installations disconnect the power supply to the Electrical equipment and discharge & connect earth. Test with meters for any availability of supply then start the work.

 

7) Function of circuit – breaker, difference between 'isolator' and circuit breaker?

Ans: The function of circuit breaker is to break the electrical continuity in the event of faults duly isolating the faulty part. Isolator is switching device, which operates in OFF load only. Circuit Breaker is switching device, which can operate in, OFF or ON load.

 

8) If a feeder circuit-breaker trips, what action is required?

Ans: First isolate the faulty feeder check the faulty area on which fault the breaker was tripped (short circuit, open circuit and earth fault) after attending the faults test for its continuity and take insulation resistance of the feeder by using megger. And take the feeder into circuit.

 

9) Different types of low-tension fuses and high-tension fuses?

Ans: There are two types of fuses they are