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Electronics and Communication Engineering - Automatic Control Systems

Exercise : Automatic Control Systems - Section 3
21.
A system has 12 poles and 2 zeros. Its high frequency asymptote in its magnitude plot has a slope of
-200 dB/decade
-240 dB/decade
-280 dB/decade
-320 dB/decade
Answer: Option
Explanation:

-(12 - 2) 20 or - 200 dB/decade.

22.
The open loop transfer function of a unity feedback system is The poles of closed loop system are at
-2, -2
-2, -1
- 2, ± j 1
- 2, 2
Answer: Option
Explanation:

for s2 + 4s + 5 = 0, the roots are - 2 ± j1.

23.
For the system of the given figure the closed loop poles are located at
s = 0 and s = -2
s = 0, s = -l ± j3
s = -1 ± j3
s = -2 and s = -1 ± j3
Answer: Option
Explanation:

Transfer function = .

The roots of equation s2 + 2s + 4 = 0 are at -1 ± 3.

24.
The system in the given figure, x(0) = 0 and x (0) = 0, At t = 0 the unit impulse δ(t) is applied X(s)
Answer: Option
Explanation:

Therefore displacement .

25.
If the polar plot, as the frequency is varied from 0 to infinity is
a semicircle
a circle
a straight line
none of the above
Answer: Option
Explanation:

At ω = 0, G(jω) = 1 ∠ 0. At ω = ∞, G(jω) = 0 ∠ -90°.

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