1. Which of the following circuit breakers has the lowest voltage range ?

SF6 circuit breaker

Air-break circuit breaker

lank type oil circuit breaker

Air-blast circuit breaker

Answer: Air-break circuit breaker

Explanation:


2. Which of the following relays is used for protection of motors against overload ?

Buchholz relay

Electromagnetic attraction type

Thermal relay

Impedance relay

Answer: Thermal relay

Explanation:


3. Breaking capacity of a circuit breaker is usually expressed in terms of ?

MV A

volts

MW

amperes

Answer: MV A

Explanation:


4. ln a circuit breaker the time duration from the instant of the fault to extinction of arc is known as ?

lead time

clearing time

lag time

operation time

Answer: clearing time

Explanation:


5. ln the event of a fault on connected circuit, a circuit breaker will operate ?

manually through control switch

automatically

depends on the design

manually

Answer: automatically

Explanation:


6. A circuit breaker will normally operate ?

when the line is to be checked

whenever fault in the line occurs

when the power is to be supplied

when the switch is put on

Answer: whenever fault in the line occurs

Explanation:


7. A lightning arrester provides ?

a high resistance path between line and ground, during operation

a low resistance path between line and ground, during operation

low impedance path between line and ground, during operation

a high impedance path between line and ground, during operation

Answer: low impedance path between line and ground, during operation

Explanation:


8. Surge modifiers are used to ?

reduce the voltage of wave front

reduce the current of wave front

reduce the steepness of wave front

modify the shape of wave front

Answer: reduce the steepness of wave front

Explanation:


9. Protection by fuses is generally not used beyond ?

100 A

20 A

200 A

50 A

Answer: 100 A

Explanation:


10. The fuse blows off by ?

arcing

melting

burning

none of the above

Answer: melting

Explanation: