# Multiple choice question for engineering

## Set 1

1. Stability of a system implies that :

a) Small changes in the system input does not result in large change in system output

b) Small changes in the system parameters does not result in large change in system output

c) Small changes in the initial conditions does not result in large change in system output

d) All of the above mentioned

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2. A linear time invariant system is stable if :

a) System in excited by the bounded input, the output is also bounded

b) In the absence of input output tends zero

c) Both a and b

d) System in excited by the bounded input, the output is not bounded

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3. Asymptotic stability is concerned with:

a) A system under influence of input

b) A system not under influence of input

c) A system under influence of output

d) A system not under influence of output

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4. Bounded input and Bounded output stability notion concerns with :

a) A system under influence of input

b) A system not under influence of input

c) A system under influence of output

d) A system not under influence of output

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5. If a system is given unbounded input then the system is:

a) Stable

b) Unstable

c) Not defined

d) Linear

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6. Linear mathematical model applies to :

a) Linear systems

b) Stable systems

c) Unstable systems

d) Non-linear systems

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7. For non-linear systems stability cannot be determined due to:

a) Possible existence of multiple equilibrium states

b) No correspondence between bounded input and bounded output stability and asymptotic stability

c) Output may be bounded for the particular bounded input but may not be bounded for the bounded inputs

d) All of the mentioned

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8. If the impulse response in absolutely integrable then the system is :

a) Absolutely stable

b) Unstable

c) Linear

d) Stable

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9. The roots of the transfer function do not have any effect on the stability of the system.

a) True

b) False

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10. Roots with higher multiplicity on the imaginary axis makes the system :

a) Absolutely stable

b) Unstable

c) Linear

d) Stable

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11. Roots on the imaginary axis makes the system :

a) Stable

b) Unstable

c) Marginally stable

d) Linear

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12. If the roots of the have negative real parts then the response is ____________

a) Stable

b) Unstable

c) Marginally stable

d) Bounded

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13. If root of the characteristic equation has positive real part the system is :

a) Stable

b) Unstable

c) Marginally stable

d) Linear

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14. A linear system can be classified as :

a) Absolutely stable

b) Conditionally stable

c) Unstable

d) All of the mentioned

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15. ___________ is a quantitative measure of how fast the transients die out in the system.

a) Absolutely stable

b) Conditionally stable

c) Unstable

d) Relative Stability

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## Set 2

1. The transfer function for the state representation of the continuous time LTI system:

dq(t)/dt=Aq(t)+Bx(t)

Y(t)=Cq(t)+Dx(t)

is given by:

a) C(sI-A)^{-1}B+D

b) B(sI-A)^{-1}B+D

c) C(sI-A)^{-1}B+A

d) D(sI-A)^{-1}B+C

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2. System transformation on function H(z) for a discrete time LTI system expressed in state variable form with zero initial condition

a) C(zI-A)^{-1}B+D

b) C(zI-A)^{-1}

c) (zI-A)^{-1}z

d) (zI-A)^{-1}

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3. State space analysis is applicable for non-linear systems and for multiple input and output systems.

a) True

b) False

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4. Assertion (A): Transfer function approach has limitation that it reveals only the system output for a input and provides no information regarding the internal state of the system.

Reason (R): There may be situations where the output of a system is stable and yet some of the system elements may have a tendency to exceed their specified ratings.

a) Both A and R are true and R is correct explanation of A

b) Both A and R are true but R is not correct explanation of A

c) A is true but R is False

d) A is False but R is True

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5. When human being tries to approach an object, his brain acts as,

a) An error measuring device

b) A controller

c) An actuator

d) An amplifier

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6. For two-phase AC servomotor, if the rotor’s resistance and reactance are respectively R and X, its length and diameter are respectively L and D then,

a) X/R and L/D are both small

b) X/R is large but L/D is small

c) X/R is small but L/D is large

d) X/R and L/D are both large

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7. Consider the following statements relating to synchro’s:

1. The rotor of the control transformer is either disc shaped

2. The rotor of the transmitter is so constructed as to have a low magnetic reluctance

3. Transmitter and control transformer pair is used as an error detector

Which of these statements are correct?

a) 1,2 and3

b) 1 and 2

c) 2 and3

d) 1 and 3

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8. Error detector:

a) Armature controlled FHP DC motor

b) A pair of synchronous transmitter and control transformer

c) Tach generator

d) Amplidyne

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9. Servomotor:

a) Armature controlled FHP DC motor

b) A pair of synchronous transmitter and control transformer

c) Tach generator

d) Amplidyne

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10. Amplifier:

a) Armature controlled FHP DC motor

b) A pair of synchronous transmitter and control transformer

c) Tach generator

d) Amplidyne

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## Set 3

1. In liquid level and electrical system analogy, voltage is considered analogous to :

a) Head

b) Liquid flow

c) Liquid flow rate

d) Air flow rate

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2. The viscous friction co-efficient, in force-voltage analogy, is analogous to:

a) Charge

b) Resistance

c) Reciprocal of inductance

d) Reciprocal of conductance

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3. In force-voltage analogy, velocity is analogous to:

a) Current

b) Charge

c) Inductance

d) Capacitance

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4. In thermal-electrical analogy charge is considered analogous to:

a) Heat flow

b) Reciprocal of heat flow

c) Reciprocal of temperature

d) Temperature

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5. Mass, in force-voltage analogy, is analogous to:

a) Charge

b) Current

c) Inductance

d) Resistance

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6. The transient response of a system is mainly due to:

a) Inertia forces

b) Internal forces

c) Stored energy

d) Friction

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7. ___________ signal will become zero when the feedback signal and reference signs are equal.

a) Input

b) Actuating

c) Feedback

d) Reference

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8. A signal other than the reference input that tends to affect the value of controlled variable is known as

a) Disturbance

b) Command

c) Control element

d) Reference input

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9. The transfer function is applicable to which of the following?

a) Linear and time-in variant systems

b) Linear and time-variant systems

c) Linear systems

d) Non-linear systems

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10. From which of the following transfer function can be obtained?

a) Signal flow graph

b) Analogous table

c) Output-input ratio

d) Standard block system

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## Set 4

1. Electrical time-constant of an armature-controlled dc servomotor is :

a) Equal to mechanical time-constant

b) Smaller than mechanical time-constant

c) Larger than mechanical time-constant

d) Not related to mechanical time-constant

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2. The open-loop transfer function of a unity feedback system is K/(s^{^}2 (s+5))The system is unstable for

a) K>5

b) K<5

c) K>0

d) All of the mentioned

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3. Peak overshoot of step-input response of an underdamped second-order system is explicitly indicative of

a) Settling time

b) Rise time

c) Natural frequency

d) Damping ratio

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4. A unity feedback system with open-loop transfer function G (s) = 4/[s(s+p)] is critically damped. The value of the parameter p is

a) 4

b) 3

c) 2

d) 1

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5. Polar plot of G (jw) = 1/jw(jw+t) is

a) Crosses the negative real axis

b) Crosses the negative imaginary axis

c) Crosses the positive imaginary axis

d) None of the mentioned

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6. In optimum time switching curve the system takes :

a) Minimum time in reaching desired location

b) Maximum time in reaching desired location

c) Never reaches

d) No desired location is present

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7. System with logic switching are :

a) Hang on

b) Bang on

c) Bang-bang

d) Hang out

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8. Zeroes are defined as:

a) Roots of the denominator of the closed loop transfer function

b) Roots of the numerator of the closed loop transfer function

c) Both of the mentioned

d) None of the mentioned

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9. As zero moves sufficiently left from the origin the effect of zero becomes less pronounced.

a) True

b) False

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10. Assertion (A): The zeroes on the real axis near the origin are generally avoided in design.

Reason (R): In a sluggish system introduction of zeroes can improve the transient response

a) Both A and R are true and R is correct explanation of A

b) Both A and R are true but R is not correct explanation of A

c) A is true but R is false

d) A is false but R is true

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## Set 5

1. With reference to root locus, the complex conjugate roots of the characteristic equation of the O.L.T.F. given below G(s)H(s) =K(s+3)/(s+1)^{2}, lie on

a) Straight line

b) Parabola

c) Circle

d) Semi-circle

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2. Determine the centroid of the root locus for the system having G(s)H(s) = K/(s+1)(s^{2}+4s+5)

a) -2.1

b) -1.78

c) -1.66

d) -1.06

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3. The loop transfer function of an LTI system is G(s)H(s) =K(s+1)(s+5)/s(s+2)(s+3). For K>0, the point on the real axis that does not belong to the root locus of the system is

a) -0.5

b) -2.5

c) -3.5

d) -5.5

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4. The angles of asymptotes of the root loci of the equation s^{3}+5s^{2}+(K+2)s+K=0 are:

a) 0° and 270°

b) 0° and 180°

c) 90° and 270°

d) 90° and 180°

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5. The intersection of asymptotes of root loci of a system with open loop transfer function G(s)H(s) = K/s(s+1)(s+3) is

a) 1.44

b) 1.33

c) -1.44

d) -1.33

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6. If a feedback control system has its open loop transfer function G(s)H(s) = K/(s-2)(s^{2}+3s+5) has the root locus plot which intersects the imaginary axis at s =0, then the value of K at this point will be

a) -5

b) 10

c) 5

d) -10

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7. The open loop transfer function of the feedback control system is given by G(s) =K(s+3)/s(s+4)^{2}(s+5)(s+6). The number of asymptotes and the centroid of asymptotes of the root loci of closed loop system is

a) 4 and (-4,0)

b) 3 and (-12,0)

c) -4 and (-4,0)

d) -3 and (-12,0)

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8. The characteristic equation of a control system is given as 1+ K(s+4)/s(s+7)(s^{2}+2s+2)=0. The real axis intercept for root locus asymptote is:

a) -2.25

b) -1

c) -1.67

d) 0

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9. The OLTF of a unity feedback system is K(s+2)(s+4)/(s+5)(s+6) the angle of arrival of the root loci as s =-2, and s =-4 respectively are:

a) 0°,180°

b) 180°,0°

c) 90°,180°

d) 180°, 90°

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10. The characteristic equation is s^{3}+14s^{2}+(45+K)s+K =0, centroid is located at (-x,0) then the value of x is ____________

a) 1

b) 2

c) 3

d) 4