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Electronics and Communication Engineering - Automatic Control Systems

Exercise : Automatic Control Systems - Section 3
26.
A second order system has damping ratio x and natural frequency ωn. The unit step response is
Answer: Option
Explanation:

.

27.
The response is
undamped
underdamped
critically damped
oscillatory
Answer: Option
Explanation:

and is less than 1.

28.
For a first order system having transfer function, the unit step response is
1 - e-t/T
e-t/T
-e-t/T - 1
1 + e-t/T
Answer: Option
Explanation:

Since the input is unit step, the response is .

29.
In the given figure, R2 >> R1. Then
Answer: Option
Explanation:

Since R2 > > R1 the term 1 + R1Cs is small as compared to 1 + R2Cs. Hence the factor can be neglected.

30.
Which of the following is not a necessary advantage of negative feedback system?
Feedback improves speed of response
Feedback improves stability
Feedback reduces effect of variations in system parameters
Feedback reduces the effect of external disturbances
Answer: Option
Explanation:

Feedback may or may not improve stability. Moreover feedback may also cause instability.

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