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# Multiple choice question for engineering

## Set 1

1. In a control system integral error compensation _______steady state error
a) Increases
b) Minimizes
c) Does not have any effect on steady state error
d) All of the mentioned

Answer: b [Reason:] Integral compensation is the phase lag compensation as it reduces or minimizes the steady state error by not affecting the damping factor but reducing the natural frequency.

2. With feedback _____ reduces.
a) System stability
b) System gain
c) System stability and gain
d) Damping

Answer: b [Reason:] With feedback damping increases and system gain reduces as they are inversely proportional to each other and for the good control system the speed of response must be high with low gain and oscillations.

3. An amplidyne can give which of the following characteristics?
a) Constant current
b) Constant voltage
c) Constant current as well as constant voltage
d) Constant current, constant voltage and constant power

Answer: d [Reason:] An amplidyne is the device so constructed so as can give constant current, voltage and power and it is the important device as single device can achieve all these features.

4. Which of the following cannot be measured by LVDT?
a) Displacement
b) Velocity
c) Acceleration
d) Pressure

Answer: d [Reason:] LVDT is the linear variable differential transformer and it is an inductive transformer and can measure displacement, velocity and acceleration but pressure cannot be measured by using LVDT.

5. __________directly converts temperature into voltage.
a) Thermocouple
b) Potentiometer
c) Gear train
d) LVDT

Answer: a [Reason:] Among all the instruments Thermocouple is the instrument that has two different metals with different temperatures and the difference in temperature is converted into the potential difference.

6. The transfer function technique is considered as inadequate under which of the following conditions?
a) Systems having complexities and nonlinearities
b) Systems having stability problems
c) Systems having multiple input disturbances
d) All of the mentioned

Answer: d [Reason:] State variable analysis is used as Transfer function approach cannot be practically used in the systems having complexities, nonlinearities, stability problems and multiple input.

7. Which of the following is the output of a thermocouple?
a) Alternating current
b) Direct current
c) A.C. voltage
d) D.C. voltage

Answer: d [Reason:] Thermocouple is the instrument that has two different metals with different temperatures and the difference in temperature is converted into the potential difference and gives output in D.C. Voltage.

8. A.C. servomotor is basically a
a) Universal motor
b) Single phase induction motor
c) Two phase induction motor
d) Three phase induction motor

Answer: c [Reason:] A.C. Servomotor is the servomotor in which the input is mainly the alternating current and is basically two phase induction motor.

9. The first order control system, which is well designed, has a
a) Small bandwidth
b) Negative time constant
c) Large negative transfer function pole
d) None of the mentioned

Answer: c [Reason:] The first order control system which is the system with maximum one root which can be at origin and has well designed large negative transfer function pole.

10. Which of the following is exhibited by Root locus diagrams?
a) The poles of the transfer function for a set of parameter values
b) The bandwidth of the system
c) The response of a system to a step input
d) The frequency response of a system

Answer: a [Reason:] Root locus diagrams is constructed by the locus traced by the gain of the system with the varying frequency and have the poles of the transfer function for a set of parameter values.

## Set 2

1. A feedback control systems has the inherent capability that its parameter can be adjusted to alter both its transient and steady state responses.
a) True
b) False

Answer: a [Reason:] Feedback’s inherent capability is that its parameter can be adjusted to alter both transient and steady state responses as together they are referred to as time responses.

2. Transient response analysis is done for_________ systems.
a) Unstable
b) Stable
c) Conditionally stable
d) Marginally stable

Answer: b [Reason:] In case the system happens to be unstable, we need not proceed with its transient response analysis.

3. The input signals to control systems are not known fully ahead of time, the characteristics of control system which suddenly strain a control system are:
a) Sudden shock
b) Sudden change
c) Constant velocity and acceleration
d) All of the mentioned

Answer: d [Reason:] System dynamic behavior for analysis and design is therefore judged and compared under standard test signals.

4. Standard test signals in control system are:
a) Impulse signal
b) Ramp signal
c) Unit step signal
d) All of the mentioned

Answer: d [Reason:] Standard test signals are impulse, ramp and unit step all of the above to test the dynamic behavior of the control system.

5. The nature of transient response is revealed by ______________
a) Sine wave
b) Cos wave
c) Tan wave
d) Test signals

Answer: d. [Reason:] The nature is dependent on system poles not on the dynamic inputs.

6. It is generally used to analyze the transient response to one of the standard test signals.
a) True
b) False

Answer: a [Reason:] For analyzing transient response mainly step is used and also other signals mainly ramp and parabolic are not used for this analysis but they are used for steady state analysis.

7. Step signal is the signal whose values is :
a) 1 for all values greater than zero
b) Indeterminate at zero
c) It is zero for time less than zero
d) All of the mentioned

Answer: d [Reason:] Step signal is the signal whose value varies from zero to level in zero time.

8. Ramp input :
a) Denotes constant velocity
b) Value increases linearly with time
c) It denotes constant velocity and varies linearly with time
d) It varies exponentially with time

Answer: c [Reason:] Ramp signal denotes constant velocity and also basic definition states that its value increases linearly with time.

9. A perfect impulse has one value at zero time instant but otherwise zero elsewhere.
a) True
b) False

Answer: b [Reason:] A perfect impulse signal has infinite value at zero but mathematically only a small pulse is taken with finite limits.

10. To find system’s response by means of convolution integral ____________ of the system is used.
a) Sum
b) Difference
c) Exponential
d) Weighing

Answer: d. [Reason:] Impulse response of a system is the inverse Laplace transfer function of its Laplace function.

## Set 3

1. Consider the following servomotors:
1. AC-two phase servomotor
2. DC servomotor
3. Hydraulic servomotor
4. Pneumatic servomotor
The correct sequence of these servomotor in increasing order of power handling capacity is:
a) 2,4,3,1
b) 4,2,3,1
c) 2,4,1,3
d) 4,2,1,3

Answer: c [Reason:] Power handling capacity is the capacity of the system where the system can handle very high power and among the given is maximum DC servomotor.

2. Open loop transfer function of a system having one zero with a positive real value is called.
a) Zero phase function
b) Negative phase function
c) Positive phase function
d) Non-minimum phase function

Answer: d [Reason:] Non-minimum phase system has zero lying on the right half but not pole and combination of the all pass and minimum phase system can be non-minimum phase system.

3. Assertion (A): The stator winding of a control transformer has higher impedance per phase
Reason (R): The rotor of control transformer is cylindrical in shape.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true and R is not correct Explanation of A
c) A is True and R is false
d) A is False and R is true

Answer: b [Reason:] The control transformer has two parts as stator which is stationary having higher impedance and rotor which was rotatory was cylindrical in shape.

4. Assertion (A): In a shunt regulator, the control element is connected in shunt with the load to achieve constant output voltage.
Reason (R): The impedance of the control element varies to keep the total current flowing through the load and the control element constant.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true and R is not correct Explanation of A
c) A is True and R is false
d) A is False and R is true

Answer: c [Reason:] Shunt regulator refers to the winding connected in shunt or parallel and to achieve constant output voltage.

5. Assertion (A): In the error detector configuration using a synchro transmitter and synchro control transformer, the latter is connected to the error amplifier.
Reason (R): Synchro control transformer has almost a uniform reluctance path between the rotor and the stator.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true and R is not correct Explanation of A
c) A is True and R is false
d) A is False and R is true

Answer: c [Reason:] Synchro control transformer is amplifier that is used to amplify the error and synchro transmitter is used to detect error.

6. A tachometer is used as an inner loop in a position control servo-system. What is the effect of feedback on the gain of the sub-loop incorporating tachometer and in the effective time constant of the system?
a) Both are reduced
b) Gain is reduced but the time constant is increased
c) Gain is increased but the time constant is reduced
d) Both are increased

Answer: a [Reason:] Tachometer is the device that is used to control the speed of motor in the control system and Feedback and effective time constant of the system both are reduced on the gain of the sub-loop.

7. If the initial conditions are inherently zero, what does it physically mean?
a) The system is at rest but stores energy
b) The system is working but does not store energy
c) The system is at rests or no energy is stored in any of its parts
d) The system is working with zero reference input

Answer: c [Reason:] A system with zero initial condition is said to be at rest since there is no stored energy.

8. In case of DC servomotor the back-emf is equivalent to an “electric friction” which tends to :
a) Improve stability of the motor
b) Slowly decrease stability of the motor
c) Vary rapidly decrease stability of the motor
d) Have no effect on stability

Answer: a [Reason:] Back emf is the voltage that is generated in absence of the input and in case of DC servomotor tends to improve the stability of the motor.

9. Consider the following statements for the pneumatic and hydraulic systems:
1. The normal operating pressure of pneumatic control is very much higher than that of hydraulic control.
2. In, pneumatic control external leakage is permissible to a certain extent, but there should no leakage in a hydraulic control.
Which of the statements given above is/are correct?
a) 1 only
b) 2 only
c) Both 1 and 2
d) Neither 1 and 2

Answer: c [Reason:] Operating pressure of pneumatic as the control,action is mainly to control the flow of air is more and also no leakage is permitted in hydraulic systems.

10. The transfer function of a LTI system is given as 1/(s+1). What is the steady-state value of the unit-impulse response?
a) 0
b) 1
c) 2
d) Infinite

Answer: a [Reason:] Steady state value is the final value and it is calculated from the final vale theorem and final value theorem is applicable for the stable systems only.

## Set 4

1. The optimization method based on dynamic programming views :
a) Control problem as the multistage decision problem
b) Control input as a time sequence of decisions
c) A sampled data system gives rise to sequence of transformations of the original state vector
d) All of the mentioned

Answer: d [Reason:] The optimization method is based on dynamic programming views control problem as the multistage decision problem and control input as time sequence of decisions.

2. The choice of control vector is considered decision of interest in :
a) Multistage process of N stages
b) Minimizing the performance index
c) Optimal policy or sequence
d) All of the mentioned

Answer: d [Reason:] The choice of control vector is considered decision of interest as it the part of multistage process of N stages and this is optimal policy or sequence and this minimizes the performance criteria.

3. The principle of invariant imbedding is :
a) The optimal control sequence is function of initial state
b) The optimal control sequence is function of number of stages N
c) Control problem is imbedded with the family of problems with fixed initial value and final state
d) The optimal control sequence is function of final state

Answer: c [Reason:] In principle of invariant imbedding we do not regard the control problem as an isolated problem with fixed initial value and N but rather imbed it with the family of problems.

4. The principle of optimality :
a) The optimal control sequence is function of initial state
b) The optimal control sequence is function of number of stages N
c) The principle maintains the N-stage decision process
d) Find one control value at a time until optimal policy is determined

Answer: The principle of optimality reduces the N-stage decision process into N-stage single state process, which state that an optimal control policy has the property that whatever the initial state and conditions are final state must follow the optimal policy.

5. The calculation in multistage process must always start from the first stage :
a) True
b) False

Answer: b [Reason:] It is permissible to find the last decision as the initial calculation step in multi stage decision process.

6. The optimal control at each state is ________ combination of states.
a) Linear
b) Non-linear
c) Time variant
d) Time invariant

Answer: a [Reason:] The optimal control at each state is linear combination of states and thus giving the linear state variable feedback control policy.

7. Feedback is :
a) Linear
b) Non-linear
c) Time variant
d) Time invariant

Answer: c [Reason:] Feedback is time varying all the optimal policy converts a linear time invariant plant with time invariant quadratic performance index into a linear time varying feedback system.

8. Realization of the optimal control policy :
a) Feedback of the state variables
b) Feedback of the control variables
c) Control constraint
d) Control function

Answer: a [Reason:] Once the optimal control policy has been determined, its realization is the second phase of the optimal control problem its realization seeks feedback of the state variables.

9. If the plant states are not variable for measurement, then it is possible to construct physical device state observer if :
a) Produces output at its plant states
b) Plants equations must satisfy the conditions of observability
c) Both a and b
d) Input must be present

Answer: c [Reason:] It produces at it output the plant states, when driven by the both the plant input and output.

10. Value of the performance index must be finite if :
a) System is controllable
b) System is observable
c) System is stable
d) System is unstable

Answer: d [Reason:] The contribution of uncontrollable and unstable states is always finite provided the control interval is always finite.

## Set 5

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

Answer: a [Reason:] Transfer Function is defined as the ratio of the Laplace output to the Laplace input with the zero initial conditions and is a unique model of the system.

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

Answer: d [Reason:] Modern control theory is also not best suited in every respect it has also some disadvantages and the major disadvantage is that it requires computational work.

3. According to the property of state transition method, e0 is equal to _____
a) I
b) A
c) e-At
d) -eAt

Answer: c [Reason:] By definition state transition matrix is defined as e-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

Answer: b [Reason:] Observability and controllability are the two methods to check the output response characteristics and observability in control engineering implies an ability to measure the state by taking measurements at output.

5. State model representation is possible using _________
a) Physical variables
b) Phase variables
c) Canonical state variables
d) All of the mentioned

Answer: d [Reason:] State model representation is the representation of the control system is the form of the state variables and state vectors and is possible using physical variables, phase variables and canonical state variables.

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

Answer: b [Reason:] Output Equations constitute the state model of a system in addition to state equations and for the complete state model mainly input model, output model and state models are required.

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

Answer: a [Reason:] State Variables are the integral part of the state variable analysis and plays a crucial role in determining the state of dynamic system.

8. Which among the following are the interconnected units of state diagram representation?
a) Scalars
c) Integrator
d) All of the mentioned

Answer: d [Reason:] Scalars, adders and integrator are the interconnected units of state diagram representation and this representation helps in determination of the state of the control system.

9. State space analysis is applicable even if the initial conditions are _____
a) Zero
b) Non-zero
c) Equal
d) Not equal

Answer: b [Reason:] State space analysis is the analysis different from the transfer function approach as it has state variables and state vectors used for the analysis and can be used even if initial conditions are non-zero.

10. Conventional control theory is applicable to ______ systems
a) SISO
b) MIMO
c) Time varying
d) Non-linear