239.  The characteristic equation of a feedback system is s3 + Ks2 + Ss + 10 = 0. For the system to be critically stable, the value of K should be
A.1
B.2
C.3
D.4

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240.  A linear second-order system with the transfer function G(s) = is S2 + 16s + 49 initially at rest and is subject to a step input signal. The response of the system will exhibit a peak overshool of
A.16%
B.9%
C.2%
D. zero

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241.  As compared to a closed ioop system, an open loop system is
A. more stable as well as more accurate
B. less stable as well as less accurate
C. more stable but less accurate
D. less stable but more accurate

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242.  Consider the following statements regarding time-domain analysis of a control system :1. Derivative control improves system's transient performance 2. Integral control does not improve system's steady state performance 3. Integral control can convert a second order system into a third order system Of these statements
A. I and 2 are correct
B. 1 and 3 are correct
C. 2 and 3 are correct
D. 1, 2 and 3 are correct.

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243.  The principles of homogenity and super-position are applied to
A. linear time variant systems
B. non-linear time variant systems
C. linear time invariant systems
D. non-linear time invariant systems

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244.  When a unit-step input is applied, a second order underdamped system has a peak overshoot of OP occurring at tmax. If another step input equal in magnitude to the peak overshoot OP is applied at t = tmax, then the system will settle down at
A. 1 + OP
B. 1 ? OP
C. OP
D.1

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245.  Which one of the following statements are true of a type 1 system having unity gain in the forward path and a unity feedback? 1. Positional error constant K is equal to infinity. 2. Acceleration error constant Ka is equal to zero. 3. Steady-state error ess to a unit step displacement input is equal to one. Select the correct answer using the codes given below Codes :
A. 1, 2 and 3
B. 1 and 2
C. 2 and 3
D. 1 and 3

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