71. A second order system has a transfer function given by:

If the system initially at rest is subjected to a unit step input at t = 0, the second peak in the response will occur at:
(a) 𝜋 sec
(b) 𝜋/3 sec
(c) 2𝜋/3 sec
(d) 𝜋/2 sec

Answer: (a)

72. A lag compensator:
1. Improves the steady state behaviour of the system
2. Speeds up the transient response
3. Nearly preserves its transient response

Which of the above statements are correct?
(a) 1, 2 and 3
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1 and 3 only

Answer: (d)

73. For a state model:

Answer: (a)

74. If the transfer function does not have pole-zero cancellation, the system can always be represented by:
(a) Unity feedback
(b) Characteristic equation
(c) Completely controllable and observable state model
(d) Neither completely controllable nor observable

Answer: (c)

75. For the given transfer function:
The corner frequencies will be respectively:
(a) 2 rad/sec and 10 rad/sec
(b) 4 rad/sec and 10 rad/sec
(c) 2 rad/sec and 5 rad/sec
(d) 4 rad/sec and 5 rad/sec

Answer: (b)

76. A single phase transformer has total core loss of 1000 𝑊 at 420 𝑉 , 60 Hz and total core loss of 400 𝑊 at 210 𝑉 , 30 Hz . The total core loss at 350 𝑉 , 50 Hz will be nearly:
(a) 593.4 𝑊
(b) 685.4 𝑊
(c) 777.8 𝑊
(d) 869.8 𝑊

Answer: (c)

77. In a transformer, the core loss is 120 𝑊 at 40 Hz and 82.5  𝑊 at 30 Hz . Both losses are measured at the same flux density. The hysteresis and eddy current losses at 50 Hz will be:
(a) 100 𝑊 and 62.5 𝑊
(b) 95 𝑊 and 62.5 𝑊
(c) 100 𝑊 and 52.5 𝑊
(d) 95 𝑊 and 52.5 𝑊

Answer: (a)

78. What is the condition for progressive winding in dc machine?

Answer: (a)

79. A dc shunt generator has an induced voltage on open circuit of 127 𝑉 . When the machine is on load, the terminal voltage is 120 𝑉 . For the field resistance of 15 Ω, armature resistance of 0.02 Ω and by ignoring armature reaction, the load current will be:
(a) 360 𝐴
(b) 354 𝐴
(c) 348 𝐴
(d) 342 𝐴

Answer: (d)

80. A 100 kVA, 6600/330 𝑉 , 50 Hz , single-phase transformer took 10 𝐴 and 436 𝑊 at 100 𝑉 in a short-circuit test, referring to the high voltage side. The voltage to be applied to the high voltage side on full-load at 0.8 𝑝.𝑓. lagging when the secondary load voltage is 330 𝑉 will be:
(a) 6914 𝑉
(b) 6734 𝑉
(c) 6452 𝑉
(d) 6172 𝑉

Answer: (b)