CIRCUIT BREAKER-3

33.Best protection is provided by HRC fuses in case of
(A) Open circuits
(B) Short circuits
(C) Overloads
(D) None of the above.
Answer B

34.For motor circuit breakers, the time of closing the cycle is
(A) 0.001 sec
(B) 0.01 sec
(C) 0.10 sec
(D) 0.003 sec.
Answer D

35.A relay used for protection of motors against overload is
(A) Impedance relay
(B) Electromagnetic attraction type
(C) Thermal relay
(D) Buchholz's relay.
Answer C

37.Fuse protection is used for current ratings up to
(A) 10 A
(B) 20 A
(C) 50 A
(D) 100 A.
Answer D

38.The fuse current in amperes is related with fuse wire diameter D as
(A) I ∞ I/D
(B) I ∞ D
(C) I ∞ D^3/2
(D) I ∞ D^2 .
Answer C

39.The acting contacts for a circuit breakers are made of
(A) Stainless steel
(B) Hard pressed carbon
(C) Porcelain
(D) Copper tungsten alloy.
Answer D

40.Ionization in a circuit breaker is not facilitated by
(A) high temperature of surrounding medium
(B) material of contacts
(C) increase of field strength
(D) increase of mean free path.
Answer B

41.Which circuit breaker is generally used in railway traction ?
(A) SF_6 gas circuit breaker
(B) Air break circuit breaker
(C) Vacuum circuit breaker
(D) Minimum oil circuit breaker.
Answer B

42.A fuse wire should have
(A) Low specific resistance and high melting point
(B) Low specific resistance and low melting point
(C) High specific resistance and high melting point
(D) High specific resistance and low melting point.
Answer D

43.Fuse wire, protection, system is usually not used beyond
(A) 10 A
(B) 25 A
(C) 50 A
(D)100A.
Answer D

44.For extra high voltage lines which circuit breaker is preferred
(A) Bulk oil circuit breaker
(B) Vacuum circuit breaker
(C) SF_6 gas circuit breaker
(D) Minimum oil circuit breaker.
Answer C

45.The number of cycles in which a high speed circuit breaker can complete its operation is
(A) 3 to 8
(B) 10 to 18
(C) 20 to 30
(D) 40 to 50.
Answer A