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180+ Control System Engineering (CSE) Solved MCQs
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 1. |
What is the algebraic sum of the reference input and feedback? |
| A. | error signal |
| B. | error detector |
| C. | controlled system |
| D. | controlled output |
| Answer» A. error signal | |
| Explanation: in the block diagram of a basic control system we see that the reference input is passed through error detector or comparator. the signal which leaves the same is the algebraic sum of reference input and feedback as the feedback wire is connected to the detector, so we call it error | |
| 2. |
Feedback control systems are referred to as closed loop systems. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: feedback control systems are also referred to as closed loop systems. in a closed loop, the actuating error signals, which is the difference between the input signal and | |
| 3. |
Which principle does the linear system follow? |
| A. | principle of energy conservation |
| B. | principle of mass conservation |
| C. | principle of electromagnetism |
| D. | principle of superposition |
| Answer» D. principle of superposition | |
| Explanation: a linear system is one who obeys the principle of superposition. the principle of superposition states that the response produced by simultaneous application of two different forcing functions is equal to the sum of individual responses. | |
| 4. |
control systems have unpredictable & non-repeatable. |
| A. | static |
| B. | dynamic |
| C. | deterministic |
| D. | stochastic |
| Answer» D. stochastic | |
| Explanation: stochastic control systems are those who have unpredictable and non- repeatable response due to involvement of random parameters. static systems is the | |
| 5. |
The pressure inside the furnace is measured by |
| A. | gauge |
| B. | thermometer |
| C. | manometer |
| D. | barometer |
| Answer» A. gauge | |
| Explanation: the pressure inside the furnace is measured by pressure gauge. in case the pressure increases or decreases beyond the desired value, the controller and the actuator will cause a change in the position of the damper. | |
| 6. |
On what difference does the pneumatic system works? |
| A. | speed |
| B. | pressure |
| C. | area |
| D. | length |
| Answer» B. pressure | |
| Explanation: a pneumatic system works due to pressure difference of air or any other gas. air at a pressure, pi is injected through the input manifold. it also consists of mass, coefficient of viscous friction and spring constant and the pressure difference created due to that, gives rise to pneumatic system. | |
| 7. |
In a thermal system, the temperature of the medium is |
| A. | increasing |
| B. | decreasing |
| C. | zero |
| D. | uniform |
| Answer» D. uniform | |
| Explanation: to analyze a thermal system and determine its transfer function the temperature of the medium should be uniform. if the temperature is varying or zero | |
| 8. |
How many parameters does process control refer to? |
| A. | 1 |
| B. | 3 |
| C. | 5 |
| D. | 7 |
| Answer» C. 5 | |
| Explanation: process control refers to control of five parameters which are level, flow, pressure, temperature, acidity of the process variable. a particular parameter has only one desired value. | |
| 9. |
What is the effect of feedback in the overall gain of the system? |
| A. | increases |
| B. | decreases |
| C. | zero |
| D. | no change |
| Answer» B. decreases | |
| Explanation: the feedback reduces the overall gain of the system. as soon as we introduce feedback in the system to make the system stable, gain is reduced. | |
| 10. |
In a temperature control system, what conversion in signal takes place? |
| A. | digital to analog |
| B. | analog to digital |
| C. | error to digital |
| D. | error to analog |
| Answer» B. analog to digital | |
| Explanation: in a temperature control system, analog to digital conversion of signals take place. automatic systems don’t understand analog signals as they only take digital inputs in the form of 0 & 1 so we use a analog to digital converter which converts the signal. | |
| 11. |
Which of the following are the not characteristics of the closed loop systems? |
| A. | it does not compensate for disturbance |
| B. | it reduces the sensitivity of plant-parameter variations |
| C. | it does not involve output measurements |
| D. | it does not has the ability to control the system transient response |
| Answer» D. it does not has the ability to control the system transient response | |
| Explanation: feedback refers to the comparison of the final output to the desired output at respective input so as to get accurate and error free result and in the system improves the transient response of the system. | |
| 12. |
Which one of the following effect in the system is not caused by negative feedback? |
| A. | reduction in gain |
| B. | increased in bandwidth |
| C. | increase in distortion |
| D. | reduction in output impedance |
| Answer» C. increase in distortion | |
| Explanation: distortion refers to the error in the open loop system and it has many oscillations in the output and is reduced in case of negative feedback. | |
| 13. |
Which of the statement is correct with regard to the bandwidth of the control loop system: |
| A. | in systems where the low frequency magnitude in 0 db on the bode diagram, the bandwidth is measured at the -3 db frequency |
| B. | the bandwidth is the measurement of the accuracy of the closed loop system |
| C. | the stability is proportional to the bandwidth |
| D. | the system with larger bandwidth provides slower step response and lower fidelity ramp response |
| Answer» A. in systems where the low frequency magnitude in 0 db on the bode diagram, the bandwidth is measured at the -3 db frequency | |
| Explanation: bandwidth is the frequency measured at the gain of 3db and for the good control system the value of the bandwidth must be large but the large value of the bandwidth increses the noise in the system. | |
| 14. |
Which of the statements are the advantages of closed loop systems over the open loop system: |
| A. | the overall reliability of the open loop system is more than the closed loop system is more than closed loop system. |
| B. | the transient response in closed loop system decays more quickly than in open loop system. |
| C. | in open loop system closing the loop increases the gain of the system |
| D. | in open loop system the effect of parameter variation is reduced |
| Answer» B. the transient response in closed loop system decays more quickly than in open loop system. | |
| Explanation: speed of response refers to the time taken to give the final output and it depends upon the rise and settling time of the transient response and speed of response of closed loop system is more than that of open loop system. | |
| 15. |
In control system excessive bandwidth is not employed because |
| A. | noise is proportional to bandwidth |
| B. | it leads to low relative stability |
| C. | it leads to slower time response |
| D. | noise is proportional to the square of the bandwidth |
| Answer» A. noise is proportional to bandwidth | |
| Explanation: in closed loop system the bandwidth of the system is more as compared to the open loop system and this is so required as higher the bandwidth means lower the selectivity and hence higher the noise. | |
| 16. |
Feedback control system is basically |
| A. | high pass filter |
| B. | low pass filter |
| C. | band pass filter |
| D. | band stop filter |
| Answer» B. low pass filter | |
| Explanation: low pass filter is mainly as integral controller and it is used as the controller in the system so as to increase the accuracy by reducing or proper eliminating the steady state error of the control system. | |
| 17. |
Which of the following will not decrease as a result of introduction of negative feedback? |
| A. | instability |
| B. | bandwidth |
| C. | overall gain |
| D. | distortion |
| Answer» B. bandwidth | |
| Explanation: bandwidth always increases due to negative feedback as the speed of response is directly proportional to the bandwidth. | |
| 18. |
As compared to the closed loop system, an open loop system is |
| A. | more stable but less accurate |
| B. | less stable as well as less accurate |
| C. | more stable as well as more accurate |
| D. | less stable but more accurate |
| Answer» A. more stable but less accurate | |
| Explanation: open loop system always follows the input but closed loop system always reduces the error irrespective of the input applied. | |
| 19. |
Open loop system is stable than closed loop system |
| A. | more |
| B. | less |
| C. | inclined |
| D. | exponential |
| Answer» A. more | |
| Explanation: open loop system always follows the input but closed loop system always reduces the error irrespective of the input applied. | |
| 20. |
For the gain feedback system, does not affect the system output if KG is : |
| A. | small |
| B. | negative |
| C. | one |
| D. | very large |
| Answer» D. very large | |
| Explanation: t(s)=kg/(1+kgh) if kg>>1: then c(s)=r(s)/h. | |
| 21. |
Determine the sensitivity of the overall transfer function for the system shown in the figure below, at w=1 rad/sec with respect to the feedback path transfer function. |
| A. | 1.11 |
| B. | -1.11 |
| C. | 2.22 |
| D. | -2.22 |
| Answer» B. -1.11 | |
| Explanation: s= -g(s)h(s)/1+g(s)h(s)-1.1. | |
| 22. |
Primary purpose of using Feedback is : |
| A. | to reduce the sensitivity of the system to parameter variations. |
| B. | to increase the bandwidth of the system |
| C. | to reduce the noise and distortion of the system |
| D. | to increase stability of the system |
| Answer» A. to reduce the sensitivity of the system to parameter variations. | |
| Explanation: the major requirement of the feedback is to reduce of the system with parameter variations that may vary with age, with changing environment. | |
| 23. |
Which of the following is not the feature of modern control system? |
| A. | quick response |
| B. | accuracy |
| C. | correct power level |
| D. | no oscillation |
| Answer» D. no oscillation | |
| Explanation: for a good control system the speed of response and stability must be high and for the slow and sluggish response is not used and undesirable. | |
| 24. |
The output of the feedback control system must be a function of: |
| A. | reference input |
| B. | reference output |
| C. | output and feedback signal |
| D. | input and feedback signal |
| Answer» D. input and feedback signal | |
| Explanation: feedback control system has the property of reducing the error and that is by differencing the output with the desired output and as the equation of the output of the system is c=gr/1+gh. | |
| 25. |
The principle of homogeneity and superposition are applied to: |
| A. | linear time invariant systems |
| B. | nonlinear time invariant systems |
| C. | linear time variant systems |
| D. | nonlinear time invariant systems |
| Answer» C. linear time variant systems | |
| Explanation: superposition theorem states that for two signals additivity and homogeneity property must be satisfied and that is applicable for the lti systems. | |
| 26. |
In continuous data systems: |
| A. | data may be continuous function of time at all points in the system |
| B. | data is necessarily a continuous function of time at all points in the system |
| C. | data is continuous at the inputs and output parts of the system but not necessarily during intermediate processing of the data |
| D. | only the reference signal is continuous function of time |
| Answer» B. data is necessarily a continuous function of time at all points in the system | |
| Explanation: continuous signals are the signals having values for the continuous time and if impulse response decays to zero as time approaches infinity, the system is stable. | |
| 27. |
A linear system at rest is subject to an input signal r(t)=1-e-t. The response of the system for t>0 is given by c(t)=1-e-2t. The transfer function of the system is: |
| A. | (s+2)/(s+1) |
| B. | (s+1)/(s+2) |
| C. | 2(s+1)/(s+2) |
| D. | (s+1)/2(s+2) |
| Answer» C. 2(s+1)/(s+2) | |
| Explanation: c(t)=1-e-2t r(s)=1/s-1/s+1 | |
| 28. |
A transfer function has two zeroes at infinity. Then the relation between the numerator(N) and the denominator degree(M) of the transfer function is: |
| A. | n=m+2 |
| B. | n=m-2 |
| C. | n=m+1 |
| D. | n=m-1 |
| Answer» B. n=m-2 | |
| Explanation: zeroes at infinity implies two poles at origin hence the type of the system is two and degree of denominator is m=n+2. | |
| 29. |
When deriving the transfer function of a linear element |
| A. | both initial conditions and loading are taken into account |
| B. | initial conditions are taken into account but the element is assumed to be not loaded |
| C. | initial conditions are assumed to be zero but loading is taken into account |
| D. | initial conditions are assumed to be zero and the element is assumed to be not loaded |
| Answer» C. initial conditions are assumed to be zero but loading is taken into account | |
| Explanation: when deriving the transfer function of a linear element only initial conditions are assumed to be zero, loading cannot be assumed to be zero. | |
| 30. |
If the initial conditions for a system 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 rest or no energy is stored in any of its part |
| D. | the system is working with zero reference input |
| Answer» C. the system is at rest or no energy is stored in any of its part | |
| Explanation: a system with zero initial condition is said to be at rest since there is no stored energy. | |
| 31. |
A signal flow graph is the graphical representation of the relationships between the variables of set linear algebraic equations. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: by definition signal flow graphs are the graphical representation of the relationships between the variables of set linear algebraic equations. | |
| 32. |
Use mason’s gain formula to find the transfer function of the given signal flow graph: |
| A. | abd/1-(ac) |
| B. | abdeg/1-(bc+ef)+bcef |
| C. | abd/1-(bc+ef)+bcef |
| D. | adcdef/1-(bc+ef)+bcef |
| Answer» B. abdeg/1-(bc+ef)+bcef | |
| Explanation: using mason’s gain formula transfer function from signal flow graph can be calculated which relates the forward path gain to the various paths and loops. | |
| 33. |
Use mason’s gain formula to find the transfer function of the following signal flow graph: |
| A. | abcd+efg/1-cd-fg-cdfg |
| B. | acdfg+bcefg/1-cd-fg-cdfg |
| C. | abef+bcd/1-cd-fg-cdfg |
| D. | adcdefg/1-cd-fg-cdfg |
| Answer» B. acdfg+bcefg/1-cd-fg-cdfg | |
| Explanation: using mason’s gain formula transfer function from signal flow graph can be calculated which relates the forward path gain to the various paths and loops. | |
| 34. |
Loop which do not possess any common node are said to be loops. |
| A. | forward gain |
| B. | touching loops |
| C. | non touching loops |
| D. | feedback gain |
| Answer» C. non touching loops | |
| Explanation: loop is the part of the network in which the branch starts from the node and comes back to the same node and non touching loop must not have any node in common. | |
| 35. |
Signal flow graphs: |
| A. | they apply to linear systems |
| B. | the equation obtained may or may not be in the form of cause or effect |
| C. | arrows are not important in the graph |
| D. | they cannot be converted back to block diagram |
| Answer» A. they apply to linear systems | |
| Explanation: signal flow graphs are used to find the transfer function of control system by converting the block diagrams into signal flow graphs or directly but cannot be used for nonlinear systems. | |
| 36. |
Signal flow graphs are reliable to find transfer function than block diagram reduction technique. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: as one set technique and formula is used here but in block diagram technique various methods are involved which increases complexity. | |
| 37. |
The relationship between an input and output variable of a signal flow graph is given by the net gain between the input and output node is known as the overall |
| A. | overall gain of the system |
| B. | stability |
| C. | bandwidth |
| D. | speed |
| Answer» A. overall gain of the system | |
| Explanation: the relationship between input and output variable of a signal flow graph is the overall gain of the system. | |
| 38. |
Use mason’s gain formula to calculate the transfer function of given figure:
|
| A. | g1/1+g2h |
| B. | g1+g2/1+g1h |
| C. | g2/1+g1h |
| D. | none of the mentioned |
| Answer» B. g1+g2/1+g1h | |
| Explanation: use mason’s gain formula to solve the signal flow graph and by using mason’s gain formula transfer function from signal flow graph can be calculated which relates the forward path gain to the various paths and loops. | |
| 39. |
Use mason’s gain formula to find the transfer function of the given figure: |
| A. | g1+g2 |
| B. | g1+g1/1-g1h+g2h |
| C. | g1+g2/1+g1h+g2h |
| D. | g1-g2 |
| Answer» C. g1+g2/1+g1h+g2h | |
| Explanation: using mason’s gain formula transfer function from signal flow graph can be calculated which relates the forward path gain to the various paths and loops. | |
| 40. |
Regenerative feedback implies feedback with |
| A. | oscillations |
| B. | step input |
| C. | negative sign |
| D. | positive sign |
| Answer» D. positive sign | |
| Explanation: regenerative feedback that is the positive feedback implies feedback with positive sign and for complementary root locus is for the regenerative feedback. | |
| 41. |
The output of a feedback control system must be a function of |
| A. | reference and output |
| B. | reference and input |
| C. | input and feedback signal |
| D. | output and feedback signal |
| Answer» D. output and feedback signal | |
| Explanation: the response of the control system is the output of the control system that depends upon the transfer function of the system and feedback system and also upon the input of the system. | |
| 42. |
A control system with excessive noise, is likely to suffer from |
| A. | saturation in amplifying stages |
| B. | loss of gain |
| C. | vibrations |
| D. | oscillations |
| Answer» A. saturation in amplifying stages | |
| Explanation: noise is defined as the unwnated output due to the input and this is | |
| 43. |
Zero initial condition for a system means |
| A. | input reference signal is zero |
| B. | zero stored energy |
| C. | initial movement of moving parts |
| D. | system is at rest and no energy is stored in any of its components |
| Answer» D. system is at rest and no energy is stored in any of its components | |
| Explanation: zero initial condition means that the system is at rest and no energy is stored in any of its component. | |
| 44. |
Transfer function of a system is used to calculate which of the following? |
| A. | the order of the system |
| B. | the time constant |
| C. | the output for any given input |
| D. | the steady state gain |
| Answer» C. the output for any given input | |
| Explanation: transfer function of a system is that ratio of laplace output to the laplace input at zero initial conditions and which is used to calculate the output for any given input. | |
| 45. |
The band width, in a feedback amplifier. |
| A. | remains unaffected |
| B. | decreases by the same amount as the gain increase |
| C. | increases by the same amount as the gain decrease |
| D. | decreases by the same amount as the gain decrease |
| Answer» C. increases by the same amount as the gain decrease | |
| Explanation: the bandwidth is defined as the difference in the higher frequency to the input frequency and increase in the bandwidth leads to the noise and in a feedback amplifier increases by the same amount as the gain decreases. | |
| 46. |
On which of the following factors does the sensitivity of a closed loop system to gain changes and load disturbances depend? |
| A. | frequency |
| B. | loop gain |
| C. | forward gain |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: sensitivity is defined as the change in the output with respect to the change in the parameter variations and the change in the input and load disturbances depends upon frequency loop gain and forward gain. | |
| 47. |
The transient response, with feedback system, |
| A. | rises slowly |
| B. | rises quickly |
| C. | decays slowly |
| D. | decays quickly |
| Answer» D. decays quickly | |
| Explanation: transient response is the response that is between time t=0 and at any time and behaviors depends upon the value of damping factor and maximum peak overshoot. | |
| 48. |
The second derivative input signals modify which of the following? |
| A. | the time constant of the system |
| B. | damping of the system |
| C. | the gain of the system |
| D. | the time constant and suppress the oscillations |
| Answer» D. the time constant and suppress the oscillations | |
| Explanation: the time constant is the time required to attain the final value of the steady state and the value if less then the speed of response will be more and second derivative input signals modify suppress the oscillations. | |
| 49. |
The transient response, yt(t), of a system becomes as t tends to infinity. |
| A. | 0 |
| B. | 1 |
| C. | infinity |
| D. | undefined |
| Answer» A. 0 | |
| Explanation: the transient response of a system slowly becomes 0 as the time, for which the input is given, increases. finally, the total response of the system is only the steady state response. | |
| 50. |
Delay time is the time required by a system to reach a quarter of its steady state value. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: the delay time is defined as the time required by the system to reach half of | |
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