objective questions (CS and PLC)

 

Unit‑1: Basics of Control System (50 Objective Questions)

  1. A control system that does not use feedback is called: A) Closed loop system B) Open loop system C) Linear system D) Nonlinear system Answer: B) Open loop system

  2. A control system that uses feedback is called: A) Open loop system B) Closed loop system C) Linear system D) Nonlinear system Answer: B) Closed loop system

  3. A system whose parameters change with time is: A) Time invariant system B) Time variant system C) Linear system D) Nonlinear system Answer: B) Time variant system

  4. A system whose parameters remain constant with time is: A) Time invariant system B) Time variant system C) Nonlinear system D) Open loop system Answer: A) Time invariant system

  5. A linear system obeys: A) Superposition principle B) Resonance principle C) Feedback principle D) Stability principle Answer: A) Superposition principle

  6. A nonlinear system does not obey: A) Superposition principle B) Feedback principle C) Stability principle D) Control principle Answer: A) Superposition principle

  7. Feedback used to reduce gain and improve stability is: A) Regenerative feedback B) Degenerative feedback C) Positive feedback D) Nonlinear feedback Answer: B) Degenerative feedback

  8. Feedback used to increase gain is: A) Degenerative feedback B) Regenerative feedback C) Negative feedback D) None of these Answer: B) Regenerative feedback

  9. Negative feedback improves: A) Stability B) Sensitivity C) Distortion D) All of these Answer: D) All of these

  10. Positive feedback reduces: A) Stability B) Gain C) Sensitivity D) Noise Answer: A) Stability

  11. Transfer function is defined as ratio of: A) Output/Input in Laplace domain B) Input/Output in Laplace domain C) Output/Input in time domain D) Input/Output in time domain Answer: A) Output/Input in Laplace domain

  12. Transfer function of an RC circuit is: A) 1/(1+sRC) B) sRC/(1+sRC) C) 1+sRC D) RC/s Answer: A) 1/(1+sRC)

  13. Transfer function of an RLC series circuit is: A) 1/(LCs²+RCs+1) B) RC/(1+sRC) C) 1+sRC D) sL/R Answer: A) 1/(LCs²+RCs+1)

  14. Poles of transfer function are values of s that make: A) Denominator zero B) Numerator zero C) Both numerator and denominator zero D) None Answer: A) Denominator zero

  15. Zeros of transfer function are values of s that make: A) Numerator zero B) Denominator zero C) Both numerator and denominator zero D) None Answer: A) Numerator zero

  16. Pole‑zero plot is drawn in: A) S‑plane B) Time domain C) Frequency domain D) Z‑plane Answer: A) S‑plane

  17. Poles on right half of S‑plane indicate: A) Stable system B) Unstable system C) Marginally stable system D) Linear system Answer: B) Unstable system

  18. Poles on left half of S‑plane indicate: A) Stable system B) Unstable system C) Nonlinear system D) Time variant system Answer: A) Stable system

  19. Poles on imaginary axis indicate: A) Marginally stable system B) Stable system C) Unstable system D) Nonlinear system Answer: A) Marginally stable system

  20. Block diagram reduction is used to: A) Simplify complex systems B) Increase complexity C) Reduce gain D) None Answer: A) Simplify complex systems

  21. Block diagram reduction helps in finding: A) Overall transfer function B) Stability only C) Gain only D) Sensitivity only Answer: A) Overall transfer function

  22. Servomotors are used in: A) Control systems B) Power generation C) Transmission lines D) None Answer: A) Control systems

  23. AC servomotor is preferred for: A) Low power applications B) High power applications C) DC supply D) None Answer: A) Low power applications

  24. DC servomotor is preferred for: A) High power applications B) Low power applications C) AC supply D) None Answer: A) High power applications

  25. Stepper motor rotates in: A) Discrete steps B) Continuous rotation C) Random motion D) None Answer: A) Discrete steps

  26. Stepper motor is widely used in: A) CNC machines B) Fans C) Pumps D) Compressors Answer: A) CNC machines

  27. Error detector in control system is: A) Potentiometer B) Synchro C) Both A and B D) None Answer: C) Both A and B

  28. Potentiometer is used as: A) Error detector B) Amplifier C) Oscillator D) None Answer: A) Error detector

  29. Synchro is used as: A) Error detector B) Amplifier C) Oscillator D) None Answer: A) Error detector

  30. Feedback element in modern control systems is: A) Optical encoder B) Potentiometer C) Synchro D) None Answer: A) Optical encoder

  31. Incremental encoder provides: A) Relative position B) Absolute position C) Speed only D) None Answer: A) Relative position

  32. Absolute encoder provides: A) Absolute position B) Relative position C) Speed only D) None Answer: A) Absolute position

  33. Optical encoder is used for: A) Position feedback B) Voltage feedback C) Current feedback D) None Answer: A) Position feedback

  34. Speed‑torque characteristic of AC servomotor is: A) Linear B) Nonlinear C) Constant D) None Answer: A) Linear

  35. Speed‑torque characteristic of DC servomotor is: A) Nonlinear B) Linear C) Constant D) None Answer: B) Linear

  36. Stepper motor torque depends on: A) Step angle B) Voltage C) Frequency D) All of these Answer: D) All of these

  37. Potentiometer works on principle of: A) Voltage division B) Current division C) Resistance division D) None Answer: A) Voltage division

  38. Synchro works on principle of: A) Electromagnetic induction B) Voltage division C) Resonance D) None Answer: A) Electromagnetic induction

  39. Control system stability depends on: A) Pole location B) Zero location C) Gain only D) None Answer: A) Pole location

  40. Sensitivity of control system is reduced by: A) Negative feedback B) Positive feedback C) High gain D) None Answer: A) Negative feedback

  41. Transfer function is valid only for: A) Linear time invariant systems B) Nonlinear systems C) Time variant systems D) None Answer: A) Linear time invariant systems

  42. Open loop system is: A) Simple but less accurate B) Complex but more accurate C) Always stable D) None Answer: A) Simple but less accurate

  43. Closed loop system is: A) More accurate but complex B) Less accurate but simple C) Always unstable D) None Answer: A) More accurate but complex

  44. Example of open loop system: A) Electric toaster B) Automatic temperature control C) Cruise control in car D) None Answer: A) Electric toaster

  45. Example of closed loop system: A) Cruise control in car B) Electric toaster C) Electric bulb D) None Answer: A) Cruise control in car

  46. Regenerative feedback is also called: A) Positive feedback B) Negative feedback C) Degenerative feedback D) None Answer: A) Positive feedback

  47. Degenerative feedback is also called: A) Negative feedback B) Positive feedback C) Regenerative feedback D) None **Answer: A) Negative

Unit‑2: Time Response Analysis (50 Objective Questions)

  1. The time response of a control system consists of: A) Transient response only B) Steady state response only C) Both transient and steady state response D) None Answer: C) Both transient and steady state response

  2. Transient response occurs: A) At initial conditions B) At final conditions C) At steady state D) None Answer: A) At initial conditions

  3. Steady state response occurs: A) After transients die out B) At initial condition C) During instability D) None Answer: A) After transients die out

  4. A step input represents: A) Sudden change in input B) Gradual change in input C) Constant slope input D) None Answer: A) Sudden change in input

  5. Laplace transform of unit step input is: A) 1/s B) 1/s² C) s D) 1 Answer: A) 1/s

  6. A ramp input represents: A) Constant velocity input B) Sudden change C) Constant acceleration D) None Answer: A) Constant velocity input

  7. Laplace transform of unit ramp input is: A) 1/s² B) 1/s C) s D) 1 Answer: A) 1/s²

  8. A parabolic input represents: A) Constant acceleration input B) Constant velocity input C) Sudden change D) None Answer: A) Constant acceleration input

  9. Laplace transform of unit parabolic input is: A) 1/s³ B) 1/s² C) 1/s D) s Answer: A) 1/s³

  10. Laplace transform of unit impulse input is: A) 1 B) 1/s C) 1/s² D) s Answer: A) 1

  11. A first order system has transfer function: A) 1/(1+Ts) B) 1/(s²+2ζωns+ωn²) C) 1/s D) None Answer: A) 1/(1+Ts)

  12. The parameter T in first order system is: A) Time constant B) Gain C) Damping ratio D) None Answer: A) Time constant

  13. Time constant represents: A) Speed of response B) Gain of system C) Stability margin D) None Answer: A) Speed of response

  14. A second order system transfer function is: A) 1/(s²+2ζωns+ωn²) B) 1/(1+Ts) C) 1/s D) None Answer: A) 1/(s²+2ζωns+ωn²)

  15. The parameter ζ in second order system is: A) Damping ratio B) Time constant C) Gain D) None Answer: A) Damping ratio

  16. If ζ = 0, the system is: A) Undamped B) Overdamped C) Critically damped D) Stable Answer: A) Undamped

  17. If ζ < 1, the system is: A) Underdamped B) Overdamped C) Critically damped D) Unstable Answer: A) Underdamped

  18. If ζ = 1, the system is: A) Critically damped B) Underdamped C) Overdamped D) Unstable Answer: A) Critically damped

  19. If ζ > 1, the system is: A) Overdamped B) Underdamped C) Critically damped D) Stable Answer: A) Overdamped

  20. Rise time is the time taken for response to rise from: A) 0% to 100% B) 10% to 90% of final value C) 50% to 100% D) None Answer: B) 10% to 90% of final value

  21. Delay time is the time taken for response to reach: A) 50% of final value B) 90% of final value C) 10% of final value D) None Answer: A) 50% of final value

  22. Peak time is the time taken to reach: A) First peak of response B) Final value C) 50% value D) None Answer: A) First peak of response

  23. Settling time is the time taken for response to remain within: A) ±2% or ±5% of final value B) ±10% of final value C) ±50% of final value D) None Answer: A) ±2% or ±5% of final value

  24. Peak overshoot is: A) Maximum deviation above final value B) Maximum deviation below final value C) Steady state error D) None Answer: A) Maximum deviation above final value

  25. Steady state error is: A) Difference between final value and desired value B) Initial error C) Transient error D) None Answer: A) Difference between final value and desired value

  26. Type of system is defined by: A) Number of integrators in forward path B) Number of poles C) Number of zeros D) None Answer: A) Number of integrators in forward path

  27. Type 0 system has: A) No integrator B) One integrator C) Two integrators D) None Answer: A) No integrator

  28. Type 1 system has: A) One integrator B) Two integrators C) No integrator D) None Answer: A) One integrator

  29. Type 2 system has: A) Two integrators B) One integrator C) No integrator D) None Answer: A) Two integrators

  30. Steady state error for step input in Type 0 system is: A) Finite B) Zero C) Infinite D) None Answer: A) Finite

  31. Steady state error for step input in Type 1 system is: A) Zero B) Finite C) Infinite D) None Answer: A) Zero

  32. Steady state error for step input in Type 2 system is: A) Zero B) Finite C) Infinite D) None Answer: A) Zero

  33. Steady state error for ramp input in Type 0 system is: A) Infinite B) Zero C) Finite D) None Answer: A) Infinite

  34. Steady state error for ramp input in Type 1 system is: A) Finite B) Zero C) Infinite D) None Answer: A) Finite

  35. Steady state error for ramp input in Type 2 system is: A) Zero B) Finite C) Infinite D) None Answer: A) Zero

  36. Steady state error for parabolic input in Type 0 system is: A) Infinite B) Zero C) Finite D) None Answer: A) Infinite

  37. Steady state error for parabolic input in Type 1 system is: A) Infinite B) Zero C) Finite D) None Answer: A) Infinite

  38. Steady state error for parabolic input in Type 2 system is: A) Finite B) Zero C) Infinite D) None Answer: A) Finite

  39. Position error constant (Kp) is used for: A) Step input B) Ramp input C) Parabolic input D) Impulse input Answer: A) Step input

  40. Velocity error constant (Kv) is used for: A) Ramp input B) Step input C) Parabolic input D) Impulse input Answer: A) Ramp input

  41. Acceleration error constant (Ka) is used for: A) Parabolic input B) Ramp input C) Step input D) Impulse input Answer: A) Parabolic input

  42. Higher system type reduces: A) Steady state error B) Stability C) Gain D) None Answer: A) Steady state error

  43. Rise time decreases with: A) Higher natural frequency B) Lower natural frequency C) Higher damping ratio D) None Answer: A) Higher natural frequency

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