# Multiple choice question for engineering

## Set 1

1. Which among the following is a unique model of a system?

a) Transfer function

b) State variable

c) Block diagram

d) Signal flow graphs

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2. Which among the following is a disadvantage of modern control theory?

a) Implementation of optimal design

b) Transfer function can also be defined for different initial conditions

c) Analysis of all systems take place

d) Necessity of computational work

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3. According to the property of state transition method, e0 is equal to _____

a) I

b) A

c) e^{-At}

d) -e^{At}

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^{-At}and this is the matrix that comes into the picture when the total response is considered that is with the free response and forced response.

4. Which mechanism in control engineering implies an ability to measure the state by taking measurements at output?

a) Controllability

b) Observability

c) Differentiability

d) Adaptability

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5. State model representation is possible using _________

a) Physical variables

b) Phase variables

c) Canonical state variables

d) All of the mentioned

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6. Which among the following constitute the state model of a system in addition to state equations?

a) Input equations

b) Output equations

c) State trajectory

d) State vector

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7. Which among the following plays a crucial role in determining the state of dynamic system?

a) State variables

b) State vector

c) State space

d) State scalar

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8. Which among the following are the interconnected units of state diagram representation?

a) Scalars

b) Adders

c) Integrator

d) All of the mentioned

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9. State space analysis is applicable even if the initial conditions are _____

a) Zero

b) Non-zero

c) Equal

d) Not equal

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10. Conventional control theory is applicable to ______ systems

a) SISO

b) MIMO

c) Time varying

d) Non-linear

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## Set 2

1. The steady state error for a unity feedback system for the input r(t) = Rt^2/2 to the system G(s) = K(s+2)/s(s^{3}+7s^{2}+12s) is

a) 0

b) 6R/K

c) ∞

d) 3R/K

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2. A control system is operated with a parabolic input as shown below

If Ka is static error constant of the system, then its dynamic error constant K2 is

a) 0.01

b) 0.02

c) 0.03

d) 0.04

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3. Find the velocity error constant of the system given below :

a) 0

b) 2

c) 4

d) ∞

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4. Consider the unity feedback system with open loop transfer function the minimum value of the steady state error to a ramp input r(t) = 6tu(t) is OLTF = K/s(s+1)(s+2)

a) 1

b) 2

c) 3

d) 4

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5. A ramp input applied to a unity feedback system results in 5% steady state error. The type number and zero frequency gain of the system are respectively

a) 1 and 20

b) 0 and 20

c) 0 and 1/20

d) 1 and 1/20

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6. A particular control system yielded a steady state error of 0.20 for unit step input. A unit integrator is cascaded to this system and unit ramp input is applied to this modified system. What is the value of steady-state error for this modified system?

a) 0.10

b) 0.15

c) 0.20

d) 0.25

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7. The error constants described are the ability to reduce the steady state errors.

a) True

b) False

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8. Systems of type higher than 2 are not employed in practice.

a) True

b) False

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9. Steady state refers to

a) Error at the steady state

b) Error at the transient state

c) Error at both state

d) Precision

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10. The disadvantages of the error constants are:

a) They do not give the information of the steady state error when the inputs are other than the three basic types

b) Error constant fail to indicate the exact manner in which the error function change with time.

c) They do not give information of the steady state error and fail to indicate the exact manner in which the error function change with time

d) They give information of the steady state error

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## Set 3

1. A variable reluctance stepper motor is constructed of ______________ material with salient poles.

a) Paramagnetic

b) Ferromagnetic

c) Diamagnetic

d) Non-magnetic

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2. In a three-stack 12/8-pole VR motor, the rotor pole pitch is

a) 15º

b) 30º

c) 45º

d) 60º

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3. A stepper motor having a resolution of 300 steps/rev and running at 2400 rpm has a pulse rate of- pps.

a) 4000

b) 8000

c) 6000

d) 10,000

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4. If a hybrid stepper motor has a rotor pitch of 36º and a step angle of 9º, the number of its phases must be

a) 4

b) 2

c) 3

d) 6

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_{s}-N

_{r})/(N

_{s}+N

_{r})*360.

5. The rotor of a stepper motor has no

a) Windings

b) Commutator

c) Brushes

d) All of the mentioned

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6. A stepping motor is a ____________ device.

a) Mechanical

b) Electrical

c) Analogue

d) Incremental

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7. The rotational speed of a given stepper motor is determined solely by the

a) Shaft load

b) Step pulse frequency

c) Polarity of stator current

d) Magnitude of stator current.

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8. Which of the following phase switching sequence represents half-step operation of a VR stepper motor ?

a) A, B, C,A……..

b) A, C, B,A…….

c) AB, BC, CA, AB……..

d) A, AB, B, BC……..

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9. A stepper motor may be considered as a ____________ converter.

a) Dc to dc

b) Ac to ac

c) Dc to ac

d) Digital-to-analogue

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10. What is the step angle of a permanent-magnet stepper motor having 8 stator poles and 4 rotor poles?

a) 60º

b) 45º

c) 30º

d) 15º

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## Set 4

1. The system with the open loop transfer function 1/s(1+s) is:

a) Type 2 and order 1

b) Type 1 and order 1

c) Type 0 and order 0

d) Type 1 and order 2

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2. The identical first order system have been cascaded non-interactively. The unit step response of the systems will be:

a) Overdamped

b) Underdamped

c) Undamped

d) Critically damped

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3. A third order system is approximated to an equivalent second order system. The rise time of this approximated lower order system will be:

a) Same as the original system for any input

b) Smaller than the original system for any input

c) Larger than the original system for any input

d) Larger or smaller depending on the input

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4. A system has a single pole at origin. Its impulse response will be:

a) Constant

b) Ramp

c) Decaying exponential

d) Oscillatory

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5. When the period of the observation is large, the type of the error will be:

a) Transient error

b) Steady state error

c) Half-power error

d) Position error constant

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6. When the unit step response of a unity feedback control system having forward path transfer function G (s) =80/s(s+18)?

a) Overdamped

b) Critically damped

c) Under damped

d) Un Damped oscillatory

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7. With negative feedback in a closed loop control system, the system sensitivity to parameter variation:

a) Increases

b) Decreases

c) Becomes zero

d) Becomes infinite

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8. An underdamped second order system with negative damping will have the roots :

a) On the negative real axis as roots

b) On the left hand side of complex plane as complex roots

c) On the right hand side of complex plane as complex conjugates

d) On the positive real axis as real roots

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9. Given a unity feedback system with G (s) =K/ s (s+4). What is the value of K for a damping ratio of 0.5?

a) 1

b) 16

c) 4

d) 2

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10. How can the steady state error can be reduced?

a) By decreasing the type of the system

b) By increasing system gain

c) By decreasing the static error constant

d) By increasing the input

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## Set 5

1. First order system is defined as :

a) Number of poles at origin

b) Order of the differential equation

c) Total number of poles of equation

d) Total number of poles and order of equation

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2. A unit step is applied at t=0 to a first order system without time delay. The response has the value of 1.264 units at t=10 mins, and 2 units at steady state. The transfer function of the system is_____________

a) 3/(1+600s)

b) 2/(1+500s)

c) 5/(1+220s)

d) 2/(1+600s)

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^{^}-t/T] K=2 0.632= 1-e

^{^}-10/T T=600 sec G(s)=2/(1+600s).

3. The transfer function of the system is G(s) =100/(s+1) (s+100). For a unit step input to the system the approximate settling time for 2% criterion is:

a) 100 sec

b) 4 sec

c) 1 sec

d) 0.01 sec

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4. If a first order system and its time response to a unit step are as shown below, the gain K is :

a) 0.25

b) 0.8

c) 1

d) 4

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^{^}(K+1/T)t] K=4

5. The unit impulse response of a system having transfer function K/(s+a) is shown below. The value of a is :

a) t1

b) t2

c) 1/t1

d) 1/t2

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^{^}-at T=1/a C(t) =0.37K T= t2=1/a.

6. A system with transfer function 1/Ts+1, subjected to a step input takes to seconds to reach 50% of step height. The value of t is :

a) 6.9s

b) 10s

c) 14.4s

d) 20s

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7.A first order system and its response to a unit step input are shown in figure below. The system parameters are____________

a) a=5 and k=12

b) a=10 and k=5

c) a=5 and k=10

d) a=8 and k=9

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_{s→0}sC(s) =K/a K/a=2 K=10.

8. Assertion (A): It is observed that step function is first derivative of a ramp function and impulse function is first derivative of a step function.

Reason (R): From the derived time response expression it is concluded that the output time response also follows the same sequence as that of input functions.

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

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

c) Both A is True but R is false

d) Both A is False but R is true

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9. Laplace transform of unit impulse signal is :

a) A/s

b) A

c) 1

d) 1/s

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10. Time response during steady state the output velocity matches with the input velocity but lags behind the input by T.

a) True

b) False