Transmission and distribution. Part – 6

51. If voltage is increased by n time, the size of the conductor would

A. Increase by n times

B. Reduce by 1/n times

C. Increase by n² times

D. Reduce by 1/n² times

52. If the length of a wire of resistance R is uniformly stretched to n times its original value its new resistance is

A. nR

B. R/n

C. N²R

D. R/n²

53. When 3-phase system is balanced, the neutral wire carries

A. No current

B. One-third of current for each phase

C. Half of current for each phase

D. None of the above

54. If the capacitance of a system is doubled then its energy stored becomes

A. 2 times

B. Unaltered

C. 4 times

D. None of the above

55. As compared to underground system the overhead system is

A. More expensive

B. Less flexible

C. More flexible

D. None of the above

56. The string efficiency of a string of suspension insulators is dependent on

A. Size of insulators

B. Number of discs in the string

C. Size of tower

D. None of the above

57. A 132 KV transmission line uses strings of insulators, each insulator rated at 25 KV. The string efficiency can maximum of 60%, the least number of insulators required in string is

A. 10

B. 9

C. 8

D. 6

58. A delta-delta, 3-phase transformer bank will have a phase shift between the primary and secondary voltages of

A. 0⁰

B. 30⁰

C. 90⁰

D. -30⁰

59. If the insulation resistance of a cable of length 10Km is 1 MΩ, its insulation resistance for 50KM length will be

A. 0.2 MΩ

B. 2 MΩ

C. 4 MΩ

D. 8 MΩ

60. In a 3-wire D.C. System, the load on the +ve side is 400A and on –ve side it is 300A. Then current in neutral wire is

A. 50A

B. 100A

C. 350A

D. 150A