Circuit Breakers and Relays 2

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Objectives for Electrician and Wireman: Circuit Breakers and Relays 2

Subject: Circuit Breakers and Relays 2

Part 2: Objective questions and answers of Circuit Breakers and Relays


Q1. Which relay hold their contacts in position after power is cutoff?

a) Read relay

b) Current relay

c) Voltage relay

d) Latching relay


Q2. What is the pick-up voltage in an over voltage relay indicated?

a) Working voltage of relay

b) Maximum voltage rating of relay

c) Minimum voltage rating of relay

d) Minimum voltage to start the relay


Q3. Which type of load is protected by G Series MCB?

a) Ovens

b) Geysers

c) Air conditioners

d) General lighting systems


Q4. Which circuit breaker is used as a switch and protective device in the domestic wiring circuit?

a) Air circuit breaker

b) Miniature circuit breaker

c) Moulded case circuit breaker

d) Earth Leakage circuit breaker


Q5. What is the function of relay to the breaking operation of circuit breaker in control circuit?

a) Sensing the fault quantities

b) Analyzing the condition of breaker

c) Controlling the Speed in case of fault

d) Interpreting the fault situation to operate breaker


Q6. What is the defect in an oil circuit breaker if the oil heats up excessively?

a) Line voltage is too high

b) Excessive load

c) Poor dielectric strength

d) Defective tripping mechanism


Q7. What is the cause for the defect if phase to ground fault on the transmission line?

a) Components failure

b) Insulation failure

c) Human error

d) Fuse failure


Q8. The fluids used in the circuit breakers should be of……

a) High dielectric strength and thermal stability

b) Non inflammable

c) Arc extinguishing ability

d) All of the above


Q9. In circuit breakers, oil as quenching medium has the advantage of…….

a) Good cooling properties and absorption of arc energy

b) High dielectric strength

c) Acting as an Insulator

d) All of the above


Q10. In a minimum oil circuit breaker, the oil is used…….

a) To act as circuit breaking medium only

b) For circuit breaking and providing insulation

c) For providing insulation only

d) For none of the above purposes


Q11. Which of the following circuit breakers has high reliability and negligible maintenance?

a) Air blast circuit breaker

b) Sulphur hexafluoride circuit breaker

c) Oil circuit breaker

d) Vacuum circuit breaker


Q12. The main purpose of filling oil in a circuit breaker is:

a) To produce insulation effect

b) To stop the ionization of the surrounding air

c) To ensure the operation of the device at a low temperature

d) To suppress the sparking produced across the connector at the time of breaking a circuit.


Q13. The circuit breaker which does not contain any serviceable part is known as:

a) Oil circuit breaker (OCB)

b) Miniature circuit breaker (MCB)

c) Air circuit breaker (ACB)

d) Air blast circuit breaker (ABCB)


Q14. In an installation, leakage current of smaller magnitudes causes…….

a) Frequent tripping of ELCB

b) Electric shock

c) Fire hazard

d) Excessive billing of energy


Q15. Miniature circuit breaker (MCB) is used in domestic and commercial installations for control and protection. The current rating of double pole and triple pole MCB is…….

a) 2.0 to 6 amperes

b) 0.5 to 60 amperes

c) 5.0 to 60 amperes

d) 6.0 to 100 amperes


Q16. MCB. Are normally rated……. ambient temperature.

a) 25 Degree C

b) 35 Degree C

c) 45 Degree C

d) 40 Degree C


Q17. Which device can be used as switch and as well as protective device?

a) Triple pole iron clad switch

b) Intermediate switch

c) Miniature circuit breaker

d) Earth leakage circuit breaker


Q18. Earth Leakage Circuit Breaker (ELCB) works on the principle of…….

a) Over load current

b) Short circuit current

c) Residual current

d) Neutral current


Q19. An ELCB must always be connected in the circuit……

a) Before energy meter

b) After energy meter

c) At the entry of supply to load after energy meter

d) Tail end of the installation


Q20. The expansion form of RCCB is…….

a) Residual Current Circuit Breaker

b) Residual Circuit Current Breaker

c) Residual Current Control Breaker

d) Residual Control Circuit Breaker


Part 2: Objective questions and answers of Circuit Breakers and Relays


Q1. Answer d


Q2. Answer d


Q3. Answer c


Q4. Answer b


Q5. Answer d


Q6. Answer c


Q7. Answer b


Q8. Answer d


Q9. Answer d


Q10. Answer a


Q11. Answer b


Q12. Answer d


Q13. Answer b


Q14. Answer d


Q15. Answer c


Q16. Answer a


Q17. Answer c


Q18. Answer c


Q19. Answer c


Q20. Answer a

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