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Ladder logic - Quiz
Contributed by: Pearson
  • 1. Who established the analogy between logical propositions and relay contact status?
A) Claude Shannon
B) Nikola Tesla
C) Alan Turing
D) John von Neumann
  • 2. What is the primary function of a coil in ladder logic?
A) Input module
B) Checker
C) Actuator
D) Rung input
  • 3. How many times can a ladder program refer to the status of a single bit?
A) Zero times
B) Twice
C) Only once
D) Any number of times
  • 4. What does a slash within a checker or actuator indicate?
A) The default state of the device at rest
B) The coil is energized
C) The circuit is broken
D) An error in the logic
  • 5. What happens if a path exists from the left side of the rung to the output?
A) The memory bit clears
B) The rung is considered true
C) The rung is considered false
D) The PLC resets
  • 6. What is the typical position of a coil on a rung?
A) The far right
B) Above the contacts
C) The far left
D) The center
  • 7. In the relay analogy, what represents the output of a rung?
A) A limit switch
B) A coil
C) A pushbutton
D) A memory module
  • 8. What do physical contacts represent in ladder logic?
A) Hard inputs from devices
B) Hard outputs to actuators
C) System clock status
D) Memory address allocation
  • 9. What happens to the output coil if no path exists on the rung?
A) The coil is energized
B) The coil remains at its last state
C) The coil is de-energized
D) The coil is bypassed
  • 10. What does each coil or contact correspond to in the programmable controller?
A) A physical wire connection
B) The CPU temperature
C) The total rung count
D) The status of a single bit
  • 11. What can a coil represent besides a physical output?
A) A communication protocol
B) A power supply failure
C) A hardware interrupt
D) An internal storage bit
  • 12. What serves as a simple analogy for checkers?
A) A push button input
B) A power source
C) A fuse
D) A light bulb output
  • 13. Besides relay rack devices, what else was shown on early ladder diagrams?
A) Software subroutines
B) User interface graphics
C) Memory storage addresses
D) External items like pumps and heaters
  • 14. What is ladder logic used for today?
A) Writing web server scripts
B) Developing operating systems
C) Developing software for PLCs
D) Managing cloud infrastructure
  • 15. Where does the name 'ladder logic' come from?
A) The visual resemblance to a ladder with rails and rungs
B) The complex nature of electrical diagrams
C) The vertical growth of the software
D) The sequential nature of hardware relays
  • 16. Which standard defines other programming languages like Structured text alongside ladder logic?
A) IEEE 802.3
B) ANSI C
C) IEC 61131-3
D) ISO 9001
  • 17. Which programming language mentioned is similar to C?
A) Structured text
B) FORTRAN
C) Ladder logic
D) Assembly
  • 18. Why was ladder logic chosen for factory engineers and technicians?
A) It was designed by computer scientists
B) It required no training in general-purpose languages like FORTRAN
C) It was the only language capable of high speeds
D) It was faster to compile than other languages
  • 19. What is a 'rung' in ladder logic considered to be?
A) A variable
B) A subroutine
C) A rule
D) A data block
  • 20. How do relay-based systems execute rules compared to PLC-based systems?
A) Only upon user request
B) Sequentially in a loop
C) In a random order
D) Simultaneously and immediately
  • 21. What term describes how a PLC executes rules?
A) Scan
B) Batch
C) Trigger
D) Interrupt
  • 22. What often accompanies a ladder logic program in complex systems?
A) A compiler suite
B) A web browser
C) A human–machine interface (HMI)
D) A hardware emulator
  • 23. In a Logical AND circuit for a bank vault door, how many key switches must be closed to activate the motor?
A) One
B) Three
C) Two
D) Zero
  • 24. What type of contacts are used for the key switches in the Logical AND vault door example?
A) Latched
B) Normally closed
C) Normally open
D) Momentary
  • 25. What type of contact is the obstruction detector in the Logical AND with NOT circuit?
A) Timed
B) Toggle
C) Normally closed
D) Normally open
  • 26. What function does the Logical OR circuit represent in the provided text?
A) Door motor = Close door AND NOT Obstruction
B) Unlock = Interior unlock AND Exterior unlock
C) Unlock = Interior unlock OR Exterior unlock
D) Door motor = Key switch 1 AND Key switch 2
  • 27. Which component is always powered in the Logical OR car door lock example?
A) The exterior switch
B) The remote receiver
C) The unlock solenoid
D) The door motor
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