# 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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