Control Systems and PLC (CSP)

Multiple Choice Questions (MCQs)

1   What is the value of Impulse input in Laplace domain?
    (A)   1
    (B)   A/s
    (C)   A/s2
    (D)   A/s3
[showhide type=”button7c1″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
2   Which terminology deals with the excitation or stimulus applied to the system from an external source for the generation of an output?
    (A)   Input signal
    (B)   Output signal
    (C)   Error signal
    (D)   Feedback signal
[showhide type=”button7c2″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
3   Basically, zeros of transfer function are the Laplace transform variable values which causes the transfer function to become ___________
    (A)   Zero
    (B)   Unity
    (C)   Infinite
    (D)   Average value
[showhide type=”button7c3″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
4   According to the property of impulse test signal, what is the value of an impulse at t = 0?
    (A)   Zero
    (B)   Unity
    (C)   Infinite
    (D)   Unpredictable
[showhide type=”button7c4″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
5   By equating the denominator of transfer function to zero, which among the following will be obtained?
    (A)   Poles
    (B)   Zeros
    (C)   Both a and b
    (D)   None of the above
[showhide type=”button7c5″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
6   The output signal is fed back at the input side from the _________point
    (A)   Summing
    (B)   Differential
    (C)   Take-off
    (D)   All of the above
[showhide type=”button7c6″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
7   Which among the following are solely responsible in determining the speed of response of control system?
    (A)   Poles
    (B)   Zeros
    (C)   Speed of input
    (D)   All of the above
[showhide type=”button7c7″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
8   If a pole is located at s = -1 in left-hand plane (LHP), how will it be represented in Laplace domain?
    (A)   1/ s + 1
    (B)   1/ s – 1
    (C)   s/ s + 1
    (D)   s/ s – 1
[showhide type=”button7c8″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
9   If an error signal e(t) of an ON-OFF controller is found to be greater than zero, what would be its output?
    (A)   10%
    (B)   50%
    (C)   80%
    (D)   100%
[showhide type=”button7c9″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: D [/showhide]
10   In P-I controller, what does an integral of a function compute?
    (A)   Density of curve
    (B)   Area under the curve
    (C)   Volume over the curve
    (D)   Circumference of curve
[showhide type=”button7c10″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
11   A good control system should be sensitive to __________
    (A)   Internal disturbances
    (B)   Environmental parameters
    (C)   Parametric variations
    (D)   Input signals (except noise)
[showhide type=”button7c11″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: D [/showhide]
12   For the transfer function given below, where does the zero of the system lie? G(s) = (5s -1) / (s2 + 5s + 4)
    (A)   s = -1 & s = -1/4
    (B)   s = -4 & s = -1
    (C)   s = 1/5
    (D)   s = -1/5
[showhide type=”button7c12″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
13   a signal is passed through an integrator, it _____the amplitude of noise signal.
    (A)   Enhances
    (B)   Reduces
    (C)   Stabilizes
    (D)   Factorizes
[showhide type=”button7c13″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
14   Laplace transform of an impulse response is regarded as _____function of the system
    (A)   Analytic
    (B)   Parabolic
    (C)   Transfer
    (D)   Hypothetical
[showhide type=”button7c14″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
15   If finite number of blocks are connected in series or cascade configuration, then how are the blocks combined algebraically?
    (A)   By addition
    (B)   By multiplication
    (C)   By differentiation
    (D)   By integration
[showhide type=”button7c15″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
16   In time domain system, which response has its existence even after an extinction of transient response?
    (A)   Step response
    (B)   Impulse response
    (C)   Steady state response
    (D)   All of the above
[showhide type=”button7c16″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
17   If a type 0 system is subjected to step input, what is its effect on steady state error?
    (A)   It increases continuously
    (B)   It remains constant
    (C)   It decreases monotonically
    (D)   It gets subjected to another input
[showhide type=”button7c17″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
18   In Routh array, if zero is found in the first column, then by which term it needs to be replaced?
    (A)   δ
    (B)   η
    (C)   σ
    (D)   ε
[showhide type=”button7c18″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: D [/showhide]
19   In a second order system, if the damping ratio is equal to ‘0’, then what would be the nature of roots?
    (A)   Imaginary
    (B)   Real and equal
    (C)   Real but not equal
    (D)   Complex conjugate
[showhide type=”button7c19″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
20   In P-D controller, the derivative action plays a significant role in increasing _______ of response.
    (A)   Time
    (B)   Distance
    (C)   Speed
    (D)   Volume
[showhide type=”button7c20″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
21   What should be the nature of bandwidth for a good control system?
    (A)   Large
    (B)   Small
    (C)   Medium
    (D)   All of the above
[showhide type=”button7c21″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
22   If an impulse response of a system is cos6t, what would be its transfer function?
    (A)   s/ (s2 –36)
    (B)   s/ (s2+36)
    (C)   s/ (s+6)
    (D)   (s2 – 6s)/ (s-6)
[showhide type=”button7c22″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
23   At summing point, more than one signal can be added or _________
    (A)   Subtracted
    (B)   Multiplied
    (C)   Both a and b
    (D)   None of the above
[showhide type=”button7c23″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
24   On which factor does the steady state error of the system depend?
    (A)   Order
    (B)   Type
    (C)   Size
    (D)   Prototype
[showhide type=”button7c24″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
25   If the system is represented by characteristic equation s3 + s2 + 3s + 3 = 0, then the system is_________
    (A)   Stable
    (B)   Unstable
    (C)   Marginally stable
    (D)   Unpredictable
[showhide type=”button7c25″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
26   Which architectural unit/block of PLC decides the sequence of different operations to be executed by means of instructions written in memory?
    (A)   Memory
    (B)   Programming software
    (C)   I/O interface
    (D)   Central Processing Unit (CPU)
[showhide type=”button7c26″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: D [/showhide]
27   The acronym PLC stands for:
    (A)   Pressure Load Control
    (B)   Programmable Logic Controller
    (C)   Pneumatic Logic Capstan
    (D)   PID Loop Controller
[showhide type=”button7c27″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
28   Ladder logic programming consists primarily of:
    (A)   Virtual relay contacts and coils
    (B)   Logic gate symbols with connecting lines
    (C)   Function blocks with connecting lines
    (D)   Text-based code
[showhide type=”button7c28″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
29   The Boolean representation of this PLC program is:


    (A)   AB’C + D’
    (B)   C + (A + B’) D’
    (C)   C + D'(A + B’)
    (D)   C (AB’ + D’)
[showhide type=”button7c29″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: D [/showhide]
30   The difference between online and offline PLC programming is . . .
    (A)   whether the PLC is running or stopped
    (B)   whether the programming PC has internet connectivity
    (C)   the type of programming cable used
    (D)   where the edited program resides
[showhide type=”button7c30″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: D [/showhide]
31   What is the largest integer number that a PLC counter function can reach if it uses a 16-bit register?
    (A)   32,768
    (B)   65,535
    (C)   32,767
    (D)   65,537
[showhide type=”button8c1″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
32   An OR function implemented in ladder logic uses:
    (A)   Normally-closed contacts in series
    (B)   Normally-open contacts in series
    (C)   Normally-open contacts in parallel
    (D)   Normally-closed contacts in parallel
[showhide type=”button8c2″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
33   An AND function implemented in ladder logic uses:
    (A)   Normally-closed contacts in series
    (B)   Normally-open contacts in series
    (C)   Normally-open contacts in parallel
    (D)   Normally-closed contacts in parallel
[showhide type=”button8c3″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
34   An NOT function implemented in ladder logic uses:
    (A)   Normally-closed contacts in series
    (B)   Normally-open contacts in series
    (C)   A single normally-open contact
    (D)   A single normally-closed contact
[showhide type=”button8c4″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: D [/showhide]
35   A NAND function implemented in ladder logic uses:
    (A)   Normally-closed contacts in series
    (B)   Normally-open contacts in series
    (C)   Normally-closed contacts in Parallel
    (D)   Normally-open contacts in Parallel
[showhide type=”button8c5″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
36   An NOR function implemented in ladder logic uses:
    (A)   Normally-closed contacts in series
    (B)   Normally-open contacts in series
    (C)   Normally-closed contacts in Parallel
    (D)   Normally-open contacts in Parallel
[showhide type=”button8c6″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
37   The most popular language for PLCs is:
    (A)   Ladder diagram
    (B)   C++
    (C)   OOP+
    (D)   VHDL
[showhide type=”button8c7″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
38   In PLC, generally relays and valves are connected to:
    (A)   Input modules
    (B)   Output modules
    (C)   both of these
    (D)   None of the above
[showhide type=”button8c8″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
39   Normally open contacts are open when:
    (A)   When Input is not energized
    (B)   When the input is energized
    (C)   When input is higher than 20 volts
    (D)   None of these
[showhide type=”button8c9″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: A [/showhide]
40   PLCs that have a fixed amount of I/O capability built into the unit are known as:
    (A)   Rack PLCs
    (B)   Modular PLCs
    (C)   Fixed or Packed PLCs
    (D)   None of these
[showhide type=”button8c10″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
41   How is the speed of operation of digital controllers to conventional relay system as compared?
    (A)   Very slow
    (B)   Very fast
    (C)   Same
    (D)   Almost similar
[showhide type=”button8c11″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
42   __________ of PLCs can be done in very little time.
    (A)   Programming
    (B)   Installation
    (C)   Commissioning
    (D)   All of the above
[showhide type=”button8c12″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: D [/showhide]
43   The PLC is used in _______.
    (A)   Machine tools
    (B)   Automated assembly equipment
    (C)   Moulding and extrusion machines
    (D)   All of the above
[showhide type=”button8c13″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: D [/showhide]
44   Which of the following cannot be an input that is given to the PLC?
    (A)   Manual switches
    (B)   Relays
    (C)   Sensors
    (D)   None of the above
[showhide type=”button8c14″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: D [/showhide]
45   PLC can be ___________ in plant to change the sequence of operation.
    (A)   Only programmed
    (B)   Only reprogrammed
    (C)   Programmed and reprogrammed
    (D)   Able to give a set point
[showhide type=”button8c15″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
46   The capability of the PLCs for complex operations is ___________ that of convention relay systems
    (A)   Poor than
    (B)   Excellent than
    (C)   As good as
    (D)   Unpredictable as
[showhide type=”button8c16″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
47   When ___________ contacts are actuated, they disrupt the power supply through them.
    (A)   Normally open type
    (B)   Normally closed type
    (C)   Both a and b
    (D)   None of the above
[showhide type=”button8c17″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]
48   The type of memory which is fast and temporarily stores the data which are immediately required for use is called as______.
    (A)   HDD
    (B)   ROM
    (C)   RAM
    (D)   SSD
[showhide type=”button8c18″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
49   Which one of the following is not a PLC manufacturer?
    (A)   Siemens
    (B)   Mitsubishi
    (C)   Microsoft
    (D)   ABB
[showhide type=”button8c19″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: C [/showhide]
50   When a relay is NOT energized:
    (A)   There is an electrical path through the NO contacts
    (B)   There is an electrical path through the NC contacts
    (C)   Neither the NO or the NC contacts have an electrical path
    (D)   Both the NO and the NC contacts have an electrical path
[showhide type=”button8c20″ more_text=”Show Answer” less_text=”Hide Answer”] Answer: Option: B [/showhide]

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