Missouri PLC Programming Certification
Exam Practice Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. What is the primary function of a Programmable Logic Controller
(PLC)?
A. To store mechanical energy
B. To control industrial automation processes
C. To cool electrical systems
D. To replace hydraulic pumps
Answer: B. To control industrial automation processes
Rationale: PLCs are industrial computers designed to monitor inputs,
execute logic, and control outputs in automated systems.
2. Which programming language is most commonly used for PLC
programming?
, A. Python
B. Java
C. Ladder Logic
D. C++
Answer: C. Ladder Logic
Rationale: Ladder Logic is the most widely used PLC programming
language because it resembles electrical relay diagrams and is easy for
technicians to understand.
3. In a PLC, what does the CPU do?
A. Stores wiring diagrams
B. Provides power to sensors
C. Executes the control program
D. Cools the PLC cabinet
Answer: C. Executes the control program
Rationale: The CPU processes input data, runs the PLC program, and
updates outputs accordingly.
4. What is the purpose of input modules in a PLC?
A. To send commands to actuators
B. To receive signals from field devices
C. To store memory data
D. To convert AC to DC power
,Answer: B. To receive signals from field devices
Rationale: Input modules receive electrical signals from switches, sensors,
and pushbuttons.
5. Which device is considered a discrete input?
A. Temperature transmitter
B. Flow transmitter
C. Pushbutton switch
D. Variable frequency drive
Answer: C. Pushbutton switch
Rationale: A pushbutton provides only ON/OFF states, making it a discrete
input device.
6. What does a normally open (NO) contact do in Ladder Logic?
A. Remains closed at all times
B. Opens when energized
C. Allows logic continuity when true
D. Prevents current flow permanently
Answer: C. Allows logic continuity when true
Rationale: A normally open instruction becomes true when the referenced
bit is energized.
7. What is the purpose of an output module?
A. To receive analog signals
, B. To control field devices
C. To program the PLC
D. To store recipes
Answer: B. To control field devices
Rationale: Output modules send signals to motors, relays, solenoids, and
lamps.
8. Which memory type retains data when PLC power is lost?
A. Volatile memory
B. RAM only
C. Non-volatile memory
D. Temporary cache
Answer: C. Non-volatile memory
Rationale: Non-volatile memory retains stored information even when
power is removed.
9. What is the scan cycle in a PLC?
A. The time required to clean sensors
B. The process of reading inputs, executing logic, and updating outputs
C. The time needed to wire a panel
D. A method of analog conversion
Answer: B. The process of reading inputs, executing logic, and updating
outputs
Exam Practice Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary function of a Programmable Logic Controller
(PLC)?
A. To store mechanical energy
B. To control industrial automation processes
C. To cool electrical systems
D. To replace hydraulic pumps
Answer: B. To control industrial automation processes
Rationale: PLCs are industrial computers designed to monitor inputs,
execute logic, and control outputs in automated systems.
2. Which programming language is most commonly used for PLC
programming?
, A. Python
B. Java
C. Ladder Logic
D. C++
Answer: C. Ladder Logic
Rationale: Ladder Logic is the most widely used PLC programming
language because it resembles electrical relay diagrams and is easy for
technicians to understand.
3. In a PLC, what does the CPU do?
A. Stores wiring diagrams
B. Provides power to sensors
C. Executes the control program
D. Cools the PLC cabinet
Answer: C. Executes the control program
Rationale: The CPU processes input data, runs the PLC program, and
updates outputs accordingly.
4. What is the purpose of input modules in a PLC?
A. To send commands to actuators
B. To receive signals from field devices
C. To store memory data
D. To convert AC to DC power
,Answer: B. To receive signals from field devices
Rationale: Input modules receive electrical signals from switches, sensors,
and pushbuttons.
5. Which device is considered a discrete input?
A. Temperature transmitter
B. Flow transmitter
C. Pushbutton switch
D. Variable frequency drive
Answer: C. Pushbutton switch
Rationale: A pushbutton provides only ON/OFF states, making it a discrete
input device.
6. What does a normally open (NO) contact do in Ladder Logic?
A. Remains closed at all times
B. Opens when energized
C. Allows logic continuity when true
D. Prevents current flow permanently
Answer: C. Allows logic continuity when true
Rationale: A normally open instruction becomes true when the referenced
bit is energized.
7. What is the purpose of an output module?
A. To receive analog signals
, B. To control field devices
C. To program the PLC
D. To store recipes
Answer: B. To control field devices
Rationale: Output modules send signals to motors, relays, solenoids, and
lamps.
8. Which memory type retains data when PLC power is lost?
A. Volatile memory
B. RAM only
C. Non-volatile memory
D. Temporary cache
Answer: C. Non-volatile memory
Rationale: Non-volatile memory retains stored information even when
power is removed.
9. What is the scan cycle in a PLC?
A. The time required to clean sensors
B. The process of reading inputs, executing logic, and updating outputs
C. The time needed to wire a panel
D. A method of analog conversion
Answer: B. The process of reading inputs, executing logic, and updating
outputs
