41. Sinusoidal oscillators are :
(a) stable
(b) unstable
(c) marginally stable
(d) conditionally stable
42. The open-loop transfer function of a control system is given by G(s) = (K(s+8))/(S( s+4)(s+a)) The smallest possible value of a for which the system is stable in the closed-loop for all positive value of K is :
(a) 0
(b) 4
(c) 8
(d) 12
43. The routh stability criterion for testing the stability of system is :
(a) an algebraic method
(b) a graphical method
(c) combination of a and b
(d) none of these
44. The open-loop transfer function of a unity negative feedback control system is given by G(s) = (K(s+4))/(S( s+2)(s+6)) For K > 4, the stability characteristics of the open-loop and closedloop configurations of the system are, respectively
(a) stable and stable
(b) unstable and stable
(c) stable and unstable
(d) unstable and unstable
45. Because of the addition of a zero to G(s)H(s), the stability of the system is :
(a) improved
(b) reduced
(c) not affected
(d) none of these
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Stability Theory » Exercise - 128. The number of sign changes in the elements of the first column of the Routh array denotes : (a) the number of zeros of the closed-loop system in the RHP (b) the number of poles of the closed-loop system in the RHP (c) the number of open-loop zeros in RHP (d) the number of open-loop poles in RHP
Stability Theory » Exercise - 136. The characteristic equation of a unity feedback system is given by s3 + s2+ 2s + 2 = 0 (a) The system has one pole in the RH of the s-plane (b) The system has two poles in the RH of the s-plane (c) The system is asymptotically stable (d) The system exhibits oscillatory response