Control System Engineering Set 6

Electrical Engineering

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This set of Control System Engineering (CSE) Multiple Choice Questions & Answers (MCQs) focuses on Control System Engineering Set 6

Q1 | For non-linear systems stability cannot be determined due to:
  • possible existence of multiple equilibrium states
  • no correspondence between bounded input and bounded output stability and asymptotic stability
  • output may be bounded for the particular bounded input but may not be bounded for the bounded inputs
  • all of the mentioned
Answer: all of the mentioned
Explaination:
for non-linear systems stability cannot be determined as asymptotic stability and bibo stability concepts cannot be applied, existence of multiple states and unbounded output for many bounded inputs.
Q2 | If the impulse response in absolutely integrable then the system is :
  • absolutely stable
  • unstable
  • linear
  • stable
Answer: absolutely stable
Explaination:
the impulse response must be absolutely integrable for the system to absolutely stable.
Q3 | The roots of the transfer function do not have any effect on the stability of the system.
  • true
  • false
Answer: false
Explaination:
the roots of transfer function also determine the stability of system as they may be real, complex and may have multiplicity of various order.
Q4 | Roots with higher multiplicity on the imaginary axis makes the system :
  • absolutely stable
  • unstable
  • linear
  • stable
Answer: unstable
Explaination:
repetitive roots on the imaginary axis makes the system unstable.
Q5 | Roots on the imaginary axis makes the system :
  • stable
  • unstable
  • marginally stable
  • linear
Answer: marginally stable
Explaination:
roots on the imaginary axis makes the system marginally stable.
Q6 | If the roots of the have negative real parts then the response is                          
  • stable
  • unstable
  • marginally stable
  • bounded
Answer: bounded
Explaination:
if the roots of the have negative
Q7 | If root of the characteristic equation has positive real part the system is :
  • stable
  • unstable
  • marginally stable
  • linear
Answer: unstable
Explaination:
the impulse response of the system is infinite when the roots of the characteristic equation has positive real part.
Q8 | A linear system can be classified as :
  • absolutely stable
  • conditionally stable
  • unstable
  • all of the mentioned
Answer: all of the mentioned
Explaination:
a system can be stable, unstable and conditionally stable also.
Q9 |                        is a quantitative measure of how fast the transients die out in the system.
  • absolutely stable
  • conditionally stable
  • unstable
  • relative stability
Answer: relative stability
Explaination:
relative stability may be measured by relative settling times of each root or pair of roots.
Q10 | Root locus of s(s+2)+K(s+4) =0 is a circle. What are the coordinates of the center of this circle?
  • -2,0
  • -3,0
  • -4,0
  • -5,0
Answer: -4,0
Explaination:
s(s+2)+k(s+4) =0
Q11 | The main objective of drawing root locus plot is :
  • to obtain a clear picture about the open loop poles and zeroes of the system
  • to obtain a clear picture about the transient response of feedback system for various values of open loop gain k
  • to determine sufficient condition for the value of ‘k’ that will make the feedback system unstable
  • both b and c
Answer: both b and c
Explaination:
the main objective of drawing root locus plot is to obtain a clear picture about the transient response of feedback system for various values of open loop gain k and to determine sufficient condition for the value of ‘k’ that will make the feedback system unstable.
Q12 | While increasing the value of gain K, the system becomes
  • less stable
  • more stable
  • unstable
  • absolute stable
Answer: less stable
Explaination:
damping factor is inversely proportional to gain on increasing gain it reduces hence makes the system less stable.
Q13 | The addition of open loop poles pulls the root locus towards:
  • the right and system becomes unstable
  • imaginary axis and system becomes marginally stable
  • the left and system becomes unstable
  • the right and system becomes unstable
Answer: the right and system becomes unstable
Answer: the right and system becomes unstable
Explaination:
the addition of open loop poles pulls the root locus towards the right and system becomes unstable.
Q14 | Root locus is used to calculate:
  • marginal stability
  • absolute stability
  • conditional stability
  • relative stability
Answer: relative stability
Explaination:
root locus is used to calculate relative stability.
Q15 | Routh Hurwitz criterion is better than root locus.
  • true
  • false
Answer: false
Explaination:
root locus is better as it require less computation process.
Q16 | Consider the following statements regarding root loci:
  • all root loci start from the respective poles of g(s) h(s)
  • all root loci end at the respective zeros of g(s) h(s) or go to infinity
  • the root loci are symmetrical about the imaginary axis of the s-plane
  • all root loci start and end from the respective poles of g(s) h(s) or go to infinity
Answer: all root loci end at the respective zeros of g(s) h(s) or go to infinity
Explaination:
all the root locus start at respective poles and end at zeroes.
Q17 | Number of roots of characteristic equation is equal to the number of                              
  • branches
  • root
  • stem
  • poles
Answer: branches
Explaination:
number of roots of characteristic equation is equal to the number of branches.
Q18 | Which of the following statements are correct?
  • root locus is for the negative feedback systems
  • complementary root locus is for the positive feedback systems
  • root locus is for the negative feedback and complementary root locus is for the positive feedback systems
  • complementary root locus is for the negative feedback systems
Answer: root locus is for the negative feedback and complementary root locus is for the positive feedback systems
Explaination:
root locus and complementary root locus are complementary to each other.
Q19 | Consider the loop transfer function K(s+6)/(s+3)(s+5) In the root locus diagram the centroid will be located at:
  • -4
  • -1
  • -2
  • -3
Answer: -2
Explaination:
centroid =sum of real part of open loop pole-sum of real part of open loop zeros/p-z.
Q20 | Which one of the following applications software’s is used to obtain an accurate root locus for?
  • lisp
  • matlab
  • dbase
  • oracle
Answer: matlab
Explaination:
matlab stands for mathematics laboratory in which the input is in the form of the matrix and is the best software for drawing root locus.
Q21 | Which one of the following is not the property of root loci?
  • the root locus is symmetrical about imaginary axis
  • they start from the open loop poles and terminate at the open loop zeroes
  • the breakaway points are determined from dk/ds = 0
  • segments of the real axis are the part of the root locus if and only is the total number of real poles and zeroes to their right is odd.
Answer: the root locus is symmetrical about imaginary axis
Explaination:
the root locus is the locus traced due to the gain of the system with changing frequency and need not be symmetrical about origin.
Q22 | The breakaway point calculated mathematically must always lie on the root locus.
  • true
  • false
Answer: true
Explaination:
the breakaway point of the two
Q23 | What is the number of the root locus segments which do not terminate on zeroes?
  • the number of poles
  • the number of zeroes
  • the difference between the number of poles and zeroes
  • the sum of the number of poles and the number of the zeroes
Answer: the difference between the number of poles and zeroes
Explaination:
the number of the root locus segments which do not lie on the root locus is the difference between the number of the poles and zeroes.
Q24 | Which one of the following are correct? The root locus is the path of the roots of the characteristic equation traced out in the s- plane?
  • as the input of the system is changed
  • as the output of the system is changed
  • as a system parameter is changed
  • as the sensitivity is changed
Answer: as a system parameter is changed
Explaination:
the root locus is the locus of the change of the system parameters of the characteristic equation traced out in the s- plane.
Q25 | If the gain of the system is reduced to a zero value, the roots of the system in the s- plane,
  • coincide with zero
  • move away from zero
  • move away from poles
  • coincide with the poles
Answer: coincide with the poles
Explaination:
the roots of the system in s plane coincides with the poles if the gain of the system is reduced to a value zero.
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