(a) To produce insulation effect
(b) To stop the ionisation of the surrounding air
(c) To ensure the operation of the device at a low temperature
(d) To suppress the sparing produced across the connected at the time of breaking a circuit
Ans. (d) To suppress the sparing produced across the connected at the time of breaking a circuit
Q.2. In circuit breakers the device used for tripping the line in the event of short-circuit is of ...... type.
(a) Magnetic
(b) Thermal
(c) Magnetic and thermal
(d) Low voltage
Ans. (a) Magnetic
Q.3. 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)
Ans. (b) Miniature circuit breaker (MCB)
Q.4. Short circuit protection is provided in the circuit breaker by ......
(a) Magnetic and thermal release
(b) Thermal release
(c) Magnetic release
(d) Low voltage release
Ans. (b) Thermal release
Q.5. 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
Ans. (d) Excessive billing of energy
Q.6. Miniature circuit breaker (MCB) are used in domestic and commercial installations for control and protection. What is the range of current rating of single pole MCBs commercially available?
(a) 2.0 to 6 amps.
(b) 0.5 to 60 amps.
(c) 1.0 to 62 amps.
(d) 6.0 to 32 amps.
Ans. (b) 0.5 to 60 amps.
Q.7. Miniature circuit breaker (MCB) are 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 amps.
(b) 0.5 to 60 amps.
(c) 5.0 to 60 amps.
(d) 6.0 to 100 amps.
Ans. (c) 5.0 to 60 amps
Q.8. Current rating of MCB selected for an air conditioner of 1 ton is ......
(a) 10/15 amps.
(b) 15/20 amps.
(c) 10/20 amps.
(d) 15/30 amps.
Ans. (a) 10/15 amps
Q.9. M.C.Bs. are normally rated ...... ambient temperature
(a) 25 degree C
(b) 35 degree C
(c) 45 degree C
(d) 40 degree C
Ans. 25 degree C
Q.10. Which one of the following is not applicable to MCB?
(a) Tamper proof as they are sealed
(b) Used for close excess current protection
(c) Used for control as well as to protect the circuit
(d) Used for coarse excess current protection
Ans. (d) Used for coarse excess current protection
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