72. The constant M-circles corresponding to the magnitude (M) of the closed loop transfer function of a linear system of values of M greater than one lie in the G-plane and to the

73. The characteristics equation of a closed-loop control system is given as s2 + 4s + 16 = 0. The resonant frequency in radians/sec. of the system is

74. The open loop transfer function of a control system is given by K(s + 10) s(s + 2)(s + a) The smallest possible value of 'a' for which this system is stable in the closed-loop for all positive values of K is

76. Consider the following statements regarding a first order system with a proportional (P) controller which exhibits an offset to a step input: 1. increase the gain of the P controller 2. add derivative mode 3. add integral mode Of these statements

77. Which one of the following statements is true for gain margin and phase margin of two closed-loop system having loop transfer fuction G (s) H (s) and exp (--s) G (s) H (s)?

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