Q.17 When the contacts of a circuit breaker are opened under abnormal condition,_____
A. sparking between the contacts
B. arc is struck between the contacts
C. contacts remains in closed position
D. isolators on both the sides of circuit breaker is opened
Ans.: B
Q.18 A current flowing during arcing period is depend upon the ____.
A. electrode resistance
B. path resistance
C. arc resistance
D. conductor or line resistance
Ans.: C
Q.19 On which of the following the arc resistance is depends?
A. length of arc
B. degree of ionization
C. cross section of arc
D. all of the above
Ans.: D
Q.20 If the arc resistance is increases then the current flowing between the contacts is ___
A. decreases
B. increases
C. remains same
D. increases as exponentially
Ans.: A
Q.21 Which of the following factors responsible for the maintenance of arc between contacts of circuit breaker?
A. distance between the contacts separation
B. ionized particles between contacts
C. potential difference between the contacts
D. all of the above
Ans.: D
Q.22 In circuit breaker the following methods is employed for arc extinguishing.
A. low resistance method
B. high resistance method
C. current zero method
D. all of the above
Ans.: D
Q.23 The transient voltage that appears across the contact at or near zero current is known as__
A. arc voltage
B. normal frequency voltage
C. restriking voltage
D. system voltage
Ans.: C
Q.24 The resistance of the arc is increases by ___
A. cooling the arc
B. lengthening the arc
C. splitting the arc
D. reducing cross sectional area of the arc
E. all of the above
Ans.: E
Q.25 Which of the following method is employed only for A.C circuit only?
A. low resistance method
B. high resistance method
C. current zero method
D. Both A or C
Ans.: D
Q.26 The resistance of the arc is ____.
A. inversely proportional to the length
B. directly proportional to the length
C. directly proportional to the square of the length
D. inversely proportional to the square of length
Ans.: B
Q.27 In cooling method of increasing of arc resistance, ___
A. cooling help in deionization of the arc path
B. increases the arc resistance
C. help in arc extinguishing
D. all of the above
Ans.: D
Q.28 The de-ionization of the medium between the arc path is can be achieved by:
A. blast effect
B. lengthening of the arc path
C. high resistance and cooling
D. all of the above
Ans.: D
Q.29 The voltage that appears across the contact of the circuit breaker during the arc is called___
A. arc voltage
B. normal frequency voltage
C. restriking voltage
D. none of the above
Ans.: A
Q.30 Arc voltage
A. its value is low near zero current point
B. its value is high near zero current point
C. its value is low near peak current point
D. its value is low near normal current point
Ans.: A