# Control Systems - Electronics Engineering test questions

## Control Systems - Electronics Engineering test questions

(1) Consider reciprocal of capacitance and torsional spring stiffness as analogous quantities. The system is considered as

(A) Torque - voltage
(B) Torque - current
(C) Force - voltage
(D) Force - current

ANSWER: Torque - voltage

(2) Under mechanical rotational system and electrical system the quantities that are not analogous are

(A) Angular velocity and current
(B) Angular displacement and charge
(C) Viscous friction and coefficient resistance
(D) Moment of inertia and conductance

ANSWER: Moment of inertia and conductance

(3) Analogies of non-electrical systems are preferred to draw over electrical systems because

(A) Electrical quantities can be easily measured
(B) Electrical systems are more easily amenable to experimental study
(C) Electrons move faster
(D) All of the above

ANSWER: Electrical systems are more easily amenable to experimental study

(4) Consider the Laplace transform F(s) = 4s / s³ + 2s² + 9s + 6 of the function f (t). The initial value of the function is

(A) 0
(B) 1
(C) 0.5
(D) None of the above

(5) Under analogy of electrical and thermal systems, the resistance under thermal quantities is expressed in terms of

(A) °C
(B) °C / (joule /min)
(C) °C / joule
(D) Min / joule °C

ANSWER: °C / (joule /min)

(6) The method of Laplace transform is applicable to equations containing

(A) Integral terms only
(B) Scalar terms only
(C) Differential terms only
(D) None of the above

ANSWER: None of the above

(7) The characteristic equation s³ + 4 s² + 8s + 12 represents a

(A) Marginally stable system
(B) Unstable system
(C) Stable system
(D) Marginally unstable system

(8) The number of roots with positive real parts for the characteristic equation 2s³ + 4 s² + 4s + 12 = 0 is

(A) One
(B) Two
(C) Three
(D) None

(9) Which one of the following roots of characteristic equations represents stable system?

(A) 2, -1, -3
(B) -1, +1
(C) (-2 + 3j), (-2 - 3j), -2
(D) -j, j, -1, 1

ANSWER: (-2 + 3j), (-2 - 3j), -2

For questions 10 to 13 refer to the data given below:

Consider second order system 2 d² y / dt² + 4 dy / dt +8y = 8x

(10) The damping ratio is

(A) 0.50
(B) 0.25
(C) 0.6
(D) 0.8

(11) The undamped natural frequency is

(A) 0
(B) 0.1
(C) 1
(D) 8

(12) The damping coefficient is

(A) 1
(B) 2
(C) 0.5
(D) 3

(13) The time constant is

(A) 0.5
(B) 0.2
(C) 0.8
(D) 1

(14) The system having characteristic equation s² + Ks + 2K – 1 = 0 will be stable if the value of K is

(A) K > 1/2
(B) K < 1/2
(C) K = 1
(D) K = 0

ANSWER: K > 1/2

(15) In the signal flow graph shown C / R is

(A) Between 0 and 1
(B) Zero
(C) Unity
(D) Infinite

(16) The system that has tendency to oscillate is

(A) Both open loop and closed loop system
(B) Open loop system
(C) Closed loop system
(D) None of the above

ANSWER: Closed loop system

(17) Transfer function is used to study

(A) Transient behaviours of systems only
(B) Steady behaviours of systems only
(C) Neither steady nor transient behaviours of systems
(D) Steady and transient behaviours of systems

ANSWER: Steady and transient behaviours of systems

(18) The transient response of a system is mainly due to

(A) Stored energy
(B) Friction
(C) Inertia forces
(D) Internal forces

(19) Routh Hurwitz criteria gives

(A) Roots in left half of s-plane
(B) Roots in right half of s-plane
(C) Roots in right half of imaginary axes
(D) Roots in left half imaginary axes

ANSWER: Roots in right half of s-plane

(20) When the feedback signal and reference sign are equal, the signal that will become zero is

(A) Reference signal
(B) Feedback signal
(C) Input signal
(D) Actuating signal

(21) The transfer function of the system is given by P (s) = 1 / s+1. The DC gain of the system is

(A) 1
(B) 10
(C) 5
(D) 100

(22) The input, which is established or varied by some means external to and independent of the feedback control system, is known as

(A) Disturbance
(B) Command
(C) Modulated signal
(D) Signal

For questions 23 and 24 refer to the data given below:

The system has transfer function P(s) = 2 / s+2, ω = 2

(23) The gain will be

(A) 0.404
(B) 0.505
(C) 0.707
(D) 0.606

(24) The phase shift will be

(A) -45°
(B) -30°
(C) -60°
(D) -50°

(25) A zero order hold is used with sampled data systems

(A) To improve the stability of the system
(B) To make it critically damped
(C) To convert it to a continuous system
(D) To reconstruct the sampled signal

ANSWER: To reconstruct the sampled signal

(26) A servomechanism with unit step input can be categorized as

(A) Type 0 system
(B) Type 1 system
(C) Type 2 system
(D) Type 3 system

ANSWER: Type 1 system

(27) _____________ must have negative real parts for a stable system.

(A) The gain factor
(B) The gain margin
(C) The system Eigen values
(D) The zeros of the transfer function

ANSWER: The system Eigen values

(28) For the transfer function G(s) = s, the Bode plot is

(A) 20 dB/decade and phase shift of π/2
(B) -20 dB/decade and constant phase shift angle
(C) Zero magnitude end phase shift
(D) Constant magnitude and constant phase shift angle

ANSWER: 20 dB/decade and phase shift of π/2

(29) The source of non-linearity is

(A) Saturation is effects in amplifiers
(B) Backlash in gears
(C) Threshold in seasons
(D) All of the above

ANSWER: All of the above

(30) In a control system, usually a differentiator is not a part it because

(A) It reduces gain margin
(B) It increases input noise
(C) It reduces damping
(D) It increases error

ANSWER: It increases input noise

(31) Under parabolic input, a type 1 system will have

(A) Actuating signal which will decrease with time
(B) Actuating signal which will increase with time
(C) Parabolic output
(D) None of the above

ANSWER: Actuating signal which will increase with time

(32) In order to produce a damping ratio of 0.5, the fraction of derivative of error needed will be

(A) 1
(B) 0.8
(C) 0.08
(D) 0.008

(33) Analysis of control systems by Laplace transform technique is not possible for

(A) Discrete time systems
(B) Linear systems
(C) Unstable continuous time systems
(D) Time invariant systems

ANSWER: Discrete time systems

(34) In a control system, integral error compensation

(A) Increases steady state error
(B) Minimizes steady state error
(C) Does not have any effect on steady state error
(D) None of the above

(35) Consider the figure given below.

For an ac servomotor, the torque speed characteristic is closer to

(A) Curve A
(B) Curve B
(C) Curve C
(D) Curve D

(36) The Loading in potentiometers can be minimized by

(A) Introducing non-linearity
(B) Introducing linearity
(C) Increasing Length of the wire
(D) Increasing reference voltage of the wire

(37) The number of root loci branches that do not terminate at zeros is given by

(A) The number of poles
(B) The number of zeros
(C) The number of zeros + the number of poles
(D) The number of zeros – the number of poles

ANSWER: The number of zeros – the number of poles

(38) Let the magnitude of the polar plot at phase crossover is A. Then the gain margin is

(A) Zero
(B) 1/A
(C) A
(D) -A

(39) Infinite resolution is present in

(A) Gall tensely potentiometer
(B) Kelvin’s double arm potentiometer
(C) Deposited field potentiometer
(D) All of the above

ANSWER: Deposited field potentiometer

(40) The effect of adding poles and zeros can be determined quickly by

(A) Nyquist plot
(B) Nicholar chart
(C) Root locus
(D) Bode plot