# Online Electronics and Communication Engineering Test - Automatic Control Systems Test

Instruction:

• This is a FREE online test. DO NOT pay money to anyone to attend this test.
• Total number of questions : 20.
• Time alloted : 30 minutes.
• Each question carry 1 mark, no negative marks.
• DO NOT refresh the page.
• All the best :-).

1.

For the system in the given figure. The transfer function C(s)/R(s) is

A.
 G1 + G2 + 1
B.
 G1 G2 + 1
C.
 G1 G2 + G2 + 1
D.
 G1 G2 + G1 + 1

Explanation:

Transfer function = (G1 + 1) G2 + 1 = G1 G2 + G2 + 1.

2.

First column elements of Routh's tabulation are 3, 5, , 2. It means that there

A.
 is one root in left half s plane
B.
 are two roots in left half s plane
C.
 are two roots in right half s plane
D.
 is one root in right half s plane

Explanation:

Since there are two sign changes in the first column, hence two roots in right half plane.

3.

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)]

Explanation:

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

4.

For the given figure,

A.
B.
C.
D.

Explanation:

For the inner loop, transfer function =

Then .

5.

The maximum shift which can be provided by a lead compensator with transfer function is

A.
 15°
B.
 30°
C.
 45°
D.
 60°

Explanation:

The maximum phase lead is given by

In this case a = 1/3. Hence sin Φm = = 0.5 or Φm = 30°.

6.

The polar plot of

A.
 does not cross real axis
B.
 crosses real axis
C.
 crosses real axis at ω = 0.7 rad/sec
D.
 crosses real axis at ω = 1.4 rad/sec

Explanation:

It does not become real at any frequency.

7.

A lead compensator is basically a

A.
 high pass filter
B.
 low pass filter
C.
 band stop filter
D.
 none of the above

Explanation:

See transfer function in the equation .

8.

For the system of the given figure, the break away and break in points are determined from the conditions . Then K =

A.
B.
C.
D.

9.

Assertion (A): For a given system only one of the static error constants is finite and significant.

Reason (R): If finite static error constant is large, the loop gain becomes smaller as ω approaches zero.

A.
 Both A and R are correct and R is correct explanation of A
B.
 Both A and R are correct but R is not correct explanation of A
C.
 A is correct but R is wrong
D.
 R is correct but A is wrong

10.

If ΔP is pressure difference, A is area of each flat surface, K is stiffness and Δx is displacement of movable surface from reference of bellows, then

A.
B.
C.
D.

11.

In a mechanical accelerometer, the steady state displacement is a measure of

A.
 constant input acceleration
B.
 constant input velocity
C.
 either (a) or (b)
D.
 neither (a) nor (b)

12.

In a synchro transmitter

A.
 input is angular position of rotor shaft and output is stator voltages
B.
 input is stator voltages and output is angular position of shaft input is rotor voltage and output is angular position of rotor shaft
C.
 input is rotor voltage and output is angular position of rotor shaft
D.
 input is angular position of rotor shaft and output is rotor voltage

13.

If block diagrams of the given figure (a) and (b) are to be equivalent, then

A.
 G2 = G1
B.
 G2 = -G1
C.
D.

14.

In control systems the word controller includes

A.
 error detector and feedback element
B.
 feedback element and control elements
C.
 error detector and control elements
D.
 error detector, control elements and feedback elements

15.

If damping ratio is 0.5, the lines joining complex poles with origin are inclined to negative real axis at

A.
 ± 90°
B.
 ± 60°
C.
 ± 45°
D.
 ± 30°

16.

Assertion (A): If points at infinity are included, G(s) has same number of poles and zeros.

Reason (R): The function has a zero at s = - 2.

A.
 Both A and R are correct and R is correct explanation of A
B.
 Both A and R are correct but R is not correct explanation of A
C.
 A is correct but R is wrong
D.
 R is correct but A is wrong

17.

Integral control action

A.
 removes offset
B.
C.
 both (a) and (b)
D.
 neither (a) nor (b)

18.

Nyquist stability criterion uses open loop frequency response characteristics.

A.
 True
B.
 False

19.

Which of the following can act as error detecting devices

1. a pair of potentiometers
2. a pair of synchros
3. a differential transformer
5. a control transformer
Select the answer using the following codes:

A.
 1, 2, 5
B.
 2, 3, 4, 5
C.
 1, 3, 4, 5
D.
 1, 2, 3, 4

20.

A conditionally stable system is stable for the value of gain between two critical values. It is unstable if

A.
 the gain is increased beyond upper critical value
B.
 the gain is decreased below lower critical value
C.
 both (a) and (b)
D.
 none of the above