1. SSC JE 22-March-2018 Shift-1
Q: Circuit breaker is used for:
A. Making the circuit only
B. Breaking the circuit only
C. Both making and breaking the circuit
D. None of the above
✅ Answer: C
Explanation: Circuit breakers are designed to make and break the circuit under normal and fault conditions.
2. SSC JE 27-Jan-2018 Shift-2
Q: The medium of arc extinction in an oil circuit breaker is:
A. Air
B. Oil
C. SF₆ gas
D. Vacuum
✅ Answer: B
Explanation: In an oil circuit breaker, insulating oil acts as the arc extinguishing medium.
3. SSC JE 22-Jan-2018 Shift-1
Q: Which of the following circuit breakers is used for high voltage applications?
A. Miniature circuit breaker
B. Air circuit breaker
C. Vacuum circuit breaker
D. SF₆ circuit breaker
✅ Answer: D
Explanation: SF₆ (sulphur hexafluoride) breakers are used for high-voltage (66 kV and above) because of excellent insulation and arc-quenching properties.
4. SSC JE 25-Jan-2018 Shift-2
Q: The main function of a circuit breaker is to:
A. Amplify power
B. Reduce voltage
C. Interrupt fault currents
D. Increase current
✅ Answer: C
Explanation: The primary job of a circuit breaker is to interrupt abnormal/fault currents and protect equipment.
5. SSC JE 24-Jan-2018 Shift-1
Q: Which of the following is not an arc quenching medium?
A. Oil
B. SF₆
C. Air
D. Copper
✅ Answer: D
Explanation: Copper is a conductor, not used for arc quenching. The other options are common arc-extinguishing mediums.
6. SSC JE 22-Jan-2018 Shift-2
Q: Which of the following circuit breakers has minimum contact wear?
A. Oil circuit breaker
B. Air blast circuit breaker
C. SF₆ circuit breaker
D. Miniature circuit breaker
✅ Answer: C
Explanation: SF₆ circuit breakers have low contact erosion due to excellent arc-quenching property of SF₆ gas.
7. SSC JE 2017
Q: In a vacuum circuit breaker, the arc is extinguished in:
A. Air
B. Oil
C. Vacuum
D. SF₆
✅ Answer: C
Explanation: In vacuum circuit breakers, arc extinction occurs in vacuum, where no ionized particles are present to sustain the arc.
8. SSC JE 2017
Q: Which type of circuit breaker is best suited for use in indoor substations?
A. Air blast CB
B. Oil CB
C. Vacuum CB
D. SF₆ CB
✅ Answer: C
Explanation: Vacuum circuit breakers are compact, low maintenance, and suitable for indoor installations up to 33 kV.
9. SSC JE 2017
Q: Which of the following statements about MCB is true?
A. It is used for high voltage
B. It is a type of fuse
C. It is reusable and trips automatically
D. It cannot be reset once tripped
✅ Answer: C
Explanation: An MCB (Miniature Circuit Breaker) trips during faults and can be reset manually.
10. SSC JE 2017
Q: Which of the following circuit breakers has the fastest operating time?
A. Oil CB
B. Air CB
C. Vacuum CB
D. SF₆ CB
✅ Answer: C
Explanation: Vacuum circuit breakers offer fast interruption (2–5 cycles) due to the absence of a medium like oil or gas.