61. All the constant N circles pass through :

(a) only origin

(b) only (-1 +j0) point

(c) both origin and (-1 = j0) point

(d) none of these

62. The Nyquist plot intersects the real axis at –a = -0.02, the gain margin is :

(a) -0.02

(b) +0.02

(c) 50

(d) cannot be estimated

63. In q(s)-plane the Nyquist plot is symmetrical about the :

(a) imaginary axis

(b) real axis

(c) origin

(d) none of these

64. The Nyquist plot inter the real axis at –a = -2, the gain margin is :

(a) 2

(b) 1/2

(c) -2

(d) cannot be estimated

65. A polar plot intersects the unit circle at a point making an angle of -45 ˚ with the negative real axis. The phase margin of the system is :

(a) -45˚

(b) 45˚

(c) -180˚ – 45˚

(d) -180˚ + 45˚

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