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Multiple choice question for engineering

Set 1

1. Which of the following is not the correct reason to select feedback compensation over cascaded one?
a) No amplification is required as the energy transfer is from higher to lower level.
b) Suitable devices are not available for compensation(series)
c) It is economical
d) Provides greater stiffness against load disturbances

View Answer

Answer: c [Reason:] Feedback compensation is the compensation obtained due to feedback and cascade refers to the cascading of blocks in the forward path and feedback compensation is not preferred over cascading as it is ecenomical.

2. Operations performed by pneumatic controllers:
a) Flexible operations
b) High torque high speed operations
c) Fire and explosion proof operation
d) All of the mentioned

View Answer

Answer: c [Reason:] Pneumatic controllers are the controllers that perform the control action to control the motion related to air and they always perform fire and explosion proof operation.

3. Operations performed by hydraulic controllers:
a) Flexible operations
b) High torque high speed operations
c) Fire and explosion proof operation
d) All of the mentioned

View Answer

Answer: b [Reason:] Hydraulic controllers are the controllers that perform the control action in which the motion is due to the water and they have high torque and high speed operations.

4. Operations performed by electronic controllers:
a) Flexible operations
b) High torque high speed operations
c) Fire and explosion proof operation
d) All of the mentioned

View Answer

Answer: a [Reason:] Electronic controllers are the most flexible controller and used over hydraulic and pneumatic controllers and they use the control action where the control is mainly handled by electronic components and can perform flexible operations as of high speed and high torque.

5. The compensator G(s) =5(1+0.3s)/1+0.1s would provide a maximum phase shift of:
a) 20°
b) 30°
c) 45°
d) 60°

View Answer

Answer: b [Reason:] The two corner frequencies are 1/0.3 and 1/0.1. The maximum phase lead occurs at mid frequency w =10/√ and maximum phase is 30°.

6. Consider the following systems:
System 1: G(s) =1/ (2s+1) and System 2: G(s) =1/ (5s+1)
The true statement regarding the system is:
a) Bandwidth of the system 1 is greater than the bandwidth of the system 2
b) Bandwidth of the system 1 is lower than the bandwidth of the system 2
c) Bandwidth of both the systems are same
d) Bandwidth of both the systems are infinite

View Answer

Answer: a [Reason:] For the system 1 B.W. is 0.5 and For the system 2 B.W. is 0.2 Hence the system 1 is having more bandwidth compared to system 2.

7. With regard to the filtering capacity the lead compensator and lag compensator are respectively:
a) Low pass and high pass filter
b) High pass and low pass filter
c) Both high pass filter
d) Both low pass filters

View Answer

Answer: b [Reason:] Lead compensator is similar to high pass filter which allows only the high frequencies to pass and rejects all the other and Lag compensator is similar to Low pass filter which allows only low frequencies to pass and rejects other.

8. What is the effect of phase lag compensation on the performance of a servo system?
a) For a given relative stability, the velocity constant is increased
b) For a given relative stability, the velocity constant is decreased
c) The bandwidth of the system is increased
d) The time response is made faster

View Answer

Answer: a [Reason:] Phase lag compensation is an integrator. It reduces the steady state error. Velocity constant =1/steady state error So velocity constant is increased.

9. A composite R-C network yielded the following transfer function when calculated from its components:
T(s) = 1+21s+20s2/1+11s+10s2. This network can be used as which one of the following?
a) Phase lead compensator
b) Phase lag compensator
c) Lag lead compensator
d) None of the mentioned

View Answer

Answer: a [Reason:] T(s) = 1+20s/1+10s. Since zero is nearer to origin than pole, it is a phase lead compensator.

10. The open loop transfer function of a plant is given as, G(s) =1/s^2-1. If the plant is operated in unity feedback configuration, then the lead compensator that can stabilize the control system is:
a) 10(s-1)/(s+2)
b) 10(s+4)/(s+2)
c) 10(s+2)/(s+10)
d) 10(s+2)/(s+10)

View Answer

Answer: a [Reason:] G(s) =1/(s-1)(s+1) The lead compensator C(s) should stabilize the plant as it is similar to the differentiator and the tendency of it is to stablize the system by increasing the damping hence remove the first term so only option (a) satisfies.

Set 2

1. A system with unity feedback having open loop transfer function as G(s) = K(s+1)/s3+as2+2s+1. What values of ‘K’ and ’a’ should be chosen so that the system oscillates ?
a) K =2, a =1
b) K =2, a =0.75
c) K =4, a =1
d) K =4, a =0.75

View Answer

Answer: b [Reason:] Solving Routh Hurwitz table whenever row of zero occurs, the roots are located symmetrically on the imaginary axis then the system response oscillates, a =1+K/2+K. If K =2 is consider then a =0.75.

2. The open loop transfer functions with unity feedback are given below for different systems.
Among these systems the unstable system is
a) G(s) =2/s+2
b) G(s) =2/s(s+2)
c) G(s) =2/(s+2)s^2
d) G(s) =2(s+1)/s(s+2)

View Answer

Answer: c [Reason:] 1+2/s^2(s+2) =0. The coefficient of‘s’ is missing. Hence the system is unstable.

3. Determine the stability of closed loop control system whose characteristic equation is
s5+s4+2s3+2s2+11s+10=0.
a) Stable
b) Marginally stable
c) Unstable
d) None of the mentioned

View Answer

Answer: b [Reason:] By Routh array s =0 and s =+j. It is having a pair of conjugate root lying on imaginary axis. System is marginally stable.

4. Determine the condition for the stability of unity feedback control system whose open loop transfer function is given by
G(s) = 2e-st/s(s+2)
a) T >1
b) T <0
c) T <1
d) T >0

View Answer

Answer: c [Reason:] G(s) =2(1-sT)/s(s+2) By Routh array analysis, for stable system, all the elements of first column need to be positive T<1.

5.Determine the value of K such that roots of characteristic equation given below lies to the left of the line s = -1. s3+10s2+18s+K.
a) K>16 and K<9
b) K<16
c) 9<K<16
d) K<9

View Answer

Answer: c [Reason:] In Routh array analysis the first column must be positive and after solving K<16 and K>9.

6. Consider a negative feedback system where G(s) =1/(s+1) and H(s) =K/s(s+2). The closed loop system is stable for
a) K>6
b) 0<K<2
c) 8<K<14
d) 0<K<6

View Answer

Answer: d [Reason:] Using Routh array, for stability k<6.

7. The characteristic equation of a feedback control system is s3+Ks2+9s+18. When the system is marginally stable, the frequency of the sustained oscillation:
a) 1
b) 1.414
c) 1.732
d) 3

View Answer

Answer: d [Reason:] Solve using Routh array and for the system to be marginally stable, K = -2. Polynomial for sustained oscillation w = 3 rad/s.

8. Consider a characteristic equation, s4+3s3+5s2+6s+k+10=0. The condition for stability is
a) K>5
b) -10<K
c) K>-4
d) -10<K<-4

View Answer

Answer: d [Reason:] Solve Roth array for the system stable, -10<K<4.

9. The polynomial s4+Ks3+s2+s+1=0 the range of K for stability is _____________
a) K>5
b) -10<K
c) K>-4
d) K-1>0

View Answer

Answer: d [Reason:] Solving using Routh array we get K-1>0 and is always negative for K>1.

10. The characteristic equation of a system is given by3s4+10s3+5s2+2=0. This system is:
a) Stable
b) Marginally stable
c) Unstable
d) Linear

View Answer

Answer: c [Reason:] There is missing coefficient so system is unstable.

Set 3

1. Assertion (A): The servo robot is a closed loop system
Reason(R): It allows for a feedback
a) Both A and R are true and R is not 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

View Answer

Answer: a [Reason:] A servomechanism, sometimes shortened to servo, is an automatic device that uses error-sensing negative feedback to correct the performance of a mechanism and is defined by its function and the servo robot is a closed loop system as it allows for a feedback.

2. A__________ translates signals from the controller into the motor voltage and current signals.
a) Servo motor
b) Servo amplifier
c) AC motor
d) DC motor

View Answer

Answer: b [Reason:] A servo amplifier monitors the feedback signal from the servomechanism and continually adjusts for deviation from expected behaviour and translates signals from the controller into the motor voltage and current signals.

3. Motors used for electronic actuator drives :
a) AC servo motors
b) DC servo motors
c) Stepper motors
d) All of the mentioned

View Answer

Answer: d [Reason:] Motors are the devices that convert the mechnical energy into electrical energy and can be used in many applications and used for electronic actuator drives are AC, DC, and stepper motors.

4. The basic components of hydraulic fluid power system are :
a) Reservoir
b) Pump and lines
c) Actuating devices and control valves
d) All of the mentioned

View Answer

Answer: d [Reason:] Hydraulic fluid power system are the systems that use the control action in which the control motion is of hydraulic motion and main components are reservoir pump and lines, actuating devices and control valves.

5. Pumps that discharge liquid in a continuous flow are referred to as non-positive displacement.
a) True
b) False

View Answer

Answer: a [Reason:] Pumps can be classified as non-positive and positive displacement and that discharge liquid in a continuous flow are referred to as non-positive displacement.

6. Connectors and fittings are used in the fluid power system :
a) To connect to various sections of the fluid lines to each other
b) To detach the fluid lines to the components of the system
c) They are used in the high pressure fluid system
d) None of the mentioned

View Answer

Answer: a [Reason:] Connectors and fittings are used in the fluid power system to connect to various sections of the fluid lines to each other and to attach the fluid lines to the components of the system.

7. ____________ is the back and forth motion of pistons inside of cylinders that provide the flow of fluid.
a) Fluid pump
b) Gravity pump
c) Reciprocating pump
d) Displacement pump

View Answer

Answer: c [Reason:] Reciprocating Pump is a type of positive pumps which includes the piston pump, plunger pump and diaphragm pump and provides the flow of fluid in the cylinder by back and forth motion of the piston.

8. Assertion (A): It is all but impossible to design a practical fluid power system without some means of controlling the volume and pressure of the fluid.
Reason (R): It is controlled and done by valves.
a) Both A and R are true and R is not 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

View Answer

Answer: a [Reason:] Valves is defined as any device by which the flow of liquid can be controlled by obstructing the flow of liquid and is all but impossible to design a practical fluid power system without some means of controlling the volume and pressure of the fluid.

9. Deciding the method of control by:
a) The purpose of valve
b) Type of fluid
c) Design and purpose of the system
d) All of the mentioned

View Answer

Answer: d [Reason:] Valves may be controlled manually, electrically, mechanically, pneumatically, hydraulically or by combination of these methods and they are used to control the flow of liquid by onstructing the flow.

10. Valves can be classified according to their use as:
a) Directional flow
b) Pressure control
c) Flow control
d) All of the mentioned

View Answer

Answer: d [Reason:] Valve is a device that is used to control the flow of liquid by obstructing the flow and they can be classified based on their structure and their requirement.

Set 4

1. Assertion (A): The servo robot is a closed loop system
Reason(R): It allows for a feedback
a) Both A and R are true and R is not 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

View Answer

Answer: a [Reason:] A servomechanism, sometimes shortened to servo, is an automatic device that uses error-sensing negative feedback to correct the performance of a mechanism and is defined by its function and the servo robot is a closed loop system as it allows for a feedback.

2. A__________ translates signals from the controller into the motor voltage and current signals.
a) Servo motor
b) Servo amplifier
c) AC motor
d) DC motor

View Answer

Answer: b [Reason:] A servo amplifier monitors the feedback signal from the servomechanism and continually adjusts for deviation from expected behaviour and translates signals from the controller into the motor voltage and current signals.

3. Motors used for electronic actuator drives :
a) AC servo motors
b) DC servo motors
c) Stepper motors
d) All of the mentioned

View Answer

Answer: d [Reason:] Motors are the devices that convert the mechnical energy into electrical energy and can be used in many applications and used for electronic actuator drives are AC, DC, and stepper motors.

4. The basic components of hydraulic fluid power system are :
a) Reservoir
b) Pump and lines
c) Actuating devices and control valves
d) All of the mentioned

View Answer

Answer: d [Reason:] Hydraulic fluid power system are the systems that use the control action in which the control motion is of hydraulic motion and main components are reservoir pump and lines, actuating devices and control valves.

5. Pumps that discharge liquid in a continuous flow are referred to as non-positive displacement.
a) True
b) False

View Answer

Answer: a [Reason:] Pumps can be classified as non-positive and positive displacement and that discharge liquid in a continuous flow are referred to as non-positive displacement.

6. Connectors and fittings are used in the fluid power system :
a) To connect to various sections of the fluid lines to each other
b) To detach the fluid lines to the components of the system
c) They are used in the high pressure fluid system
d) None of the mentioned

View Answer

Answer: a [Reason:] Connectors and fittings are used in the fluid power system to connect to various sections of the fluid lines to each other and to attach the fluid lines to the components of the system.

7. ____________ is the back and forth motion of pistons inside of cylinders that provide the flow of fluid.
a) Fluid pump
b) Gravity pump
c) Reciprocating pump
d) Displacement pump

View Answer

Answer: c [Reason:] Reciprocating Pump is a type of positive pumps which includes the piston pump, plunger pump and diaphragm pump and provides the flow of fluid in the cylinder by back and forth motion of the piston.

8. Assertion (A): It is all but impossible to design a practical fluid power system without some means of controlling the volume and pressure of the fluid.
Reason (R): It is controlled and done by valves.
a) Both A and R are true and R is not 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

View Answer

Answer: a [Reason:] Valves is defined as any device by which the flow of liquid can be controlled by obstructing the flow of liquid and is all but impossible to design a practical fluid power system without some means of controlling the volume and pressure of the fluid.

9. Deciding the method of control by:
a) The purpose of valve
b) Type of fluid
c) Design and purpose of the system
d) All of the mentioned

View Answer

Answer: d [Reason:] Valves may be controlled manually, electrically, mechanically, pneumatically, hydraulically or by combination of these methods and they are used to control the flow of liquid by onstructing the flow.

10. Valves can be classified according to their use as:
a) Directional flow
b) Pressure control
c) Flow control
d) All of the mentioned

View Answer

Answer: d [Reason:] Valve is a device that is used to control the flow of liquid by obstructing the flow and they can be classified based on their structure and their requirement.

Set 5

1. Which one of the following statements is not correct?
a) Root loci can be used for analyzing stability and transient performance
b) Root loci provide insight into system stability and performance
c) Shape of the root locus gives idea of type of controller needed to meet design specification
d) Root locus can be used to handle more than one variable at a time

View Answer

Answer: d [Reason:] For more than one variable state space is used.

2. Root locus of s(s+2)+K(s+4) =0 is a circle. What are the coordinates of the center of this circle?
a) -2,0
b) -3,0
c) -4,0
d) -5,0

View Answer

Answer: c [Reason:] s(s+2)+K(s+4) =0 1+K(s+4)/s(s+2) =0. G(s)H(s) =K(s+b)/s(s+a) Centre =(-b,0) =(-4,0).

3. The main objective of drawing root locus plot is :
a) To obtain a clear picture about the open loop poles and zeroes of the system
b) To obtain a clear picture about the transient response of feedback system for various values of open loop gain K
c) To determine sufficient condition for the value of ‘K’ that will make the feedback system unstable
d) Both b and c

View Answer

Answer: d [Reason:] 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.

4. While increasing the value of gain K, the system becomes
a) Less stable
b) More stable
c) Unstable
d) Absolute stable

View Answer

Answer: a [Reason:] Damping factor is inversely proportional to gain on increasing gain it reduces hence makes the system less stable.

5. The addition of open loop poles pulls the root locus towards:
a) The right and system becomes unstable
b) Imaginary axis and system becomes marginally stable
c) The left and system becomes unstable
d) The right and system becomes unstable

View Answer

Answer: d [Reason:] The addition of open loop poles pulls the root locus towards the right and system becomes unstable.

6. Root locus is used to calculate:
a) Marginal stability
b) Absolute stability
c) Conditional stability
d) Relative stability

View Answer

Answer: d [Reason:] Root locus is used to calculate relative stability.

7. Routh Hurwitz criterion is better than root locus.
a) True
b) False

View Answer

Answer: b [Reason:] Root locus is better as it require less computation process.

8. Consider the following statements regarding root loci:
a) All root loci start from the respective poles of G(s) H(s)
b) All root loci end at the respective zeros of G(s) H(s) or go to infinity
c) The root loci are symmetrical about the imaginary axis of the s-plane
d) All root loci start and end from the respective poles of G(s) H(s) or go to infinity

View Answer

Answer: b [Reason:] All the root locus start at respective poles and end at zeroes.

9. Number of roots of characteristic equation is equal to the number of ______________
a) Branches
b) Root
c) Stem
d) Poles

View Answer

Answer: a [Reason:] Number of roots of characteristic equation is equal to the number of branches.

10. Which of the following statements are correct?
a) Root locus is for the negative feedback systems
b) Complementary root locus is for the positive feedback systems
c) Root locus is for the negative feedback and Complementary root locus is for the positive feedback systems
d) Complementary root locus is for the negative feedback systems

View Answer

Answer: c [Reason:] Root locus and Complementary root locus are complementary to each other.