Electronics and Communication Engineering - Automatic Control Systems

Exercise :: Automatic Control Systems - Section 1

36.

In Bode diagram (log magnitude plot) the factor in the transfer function gives a line having slope

A.	-20 dB per octave
B.	-10 dB per octave
C.	-6 dB per octave
D.	-2 dB per octave

Answer: Option C

Explanation:

For term the slope is -20 dB/decade or -6 dB/octave because - 20 log 2 = -6 dB.

37.

In the given figure the input is x(t) = A sin ωt. The steady state output y(t) =

A.	A sin (ωt + φ) where φ = tan^-1 \|G(jω)\|
B.	\|G(jω)\| A sin [ωt + ∠G(jω)]
C.	\|G(jω)\| A sin [2ωt + ∠G(jω)]
D.	A G(jω) sin [ωt + ∠G(jω)]

Answer: Option B

Explanation:

The magnitudes A and G(jω) are multiplied and phase angles are added.

38.

In the given figure x₆ =

A.	de(ax₁ + bx₂ + cx₃)
B.	(a + b + c) (x₁ + x₂ + x₃) (d + e)
C.	(ax₁ + bx₂ + cx₃) (d + e)
D.	a b c d e (x₁ + x₂ + x₃)

Answer: Option A

Explanation:

The input x₁ is multiplied by a, x₂, by b and x₃ by c. The sum total is multiplied by d and e.

39.

A negative feedback system has . The closed loop system is stable for

A.	K > 20
B.	15 < K < 19
C.	8 ≤ K ≤ 14
D.	K < 6

Answer: Option D

Explanation:

Find characteristic equation.

40.

For the given figure,

A.
B.
C.
D.

Answer: Option B

Explanation:

For the inner loop, transfer function =

Then .

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