Top 10 PLC MCQ questions asked in previous year paper

Programmable Logic controller Multiple Choice Question

Top 10 PLC Programmable logic controller questions asked in various competitive exam. Please give this exam. This is free mock test and check your score.

First give this exam. If your answer is wrong then check below video for detail description of question

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Series#1 ( Top 10 Questions )

Question 1 The acronym PLC stands for:

  1. Pressure Load Control
  2. Programmable Logic Controller
  3. Pneumatic Logic Capstan
  4. PID Loop Controller
  5. Pressure Loss Chamber

Answer: Programmable Logic Controller

Question 2 Ladder logic programming consists primarily of:

  1. Virtual relay contacts and coils
  2. Logic gate symbols with connecting lines
  3. Function blocks with connecting lines
  4. Text-based code
  5. Hieroglyphics

Answer: Virtual relay contacts and coils

Question 3 In a PLC, the scan time refers to the amount of time in which …..

  1. The technician enters the program
  2. Timers and counters are indexed by
  3. One “rung” of ladder logic takes to complete
  4. The entire program takes to execute
  5. Transmitted data communications must finish

Answer: The entire program takes to execute

Question 4 Identify the problem in this motor control PLC program:

  1. Coil
  2. Start contact
  3. Seal-in contact
  4. Stop contact
  5. Power source

Answer: Seal-in contact

Question 5 The Boolean representation of this PLC program is:

  1. ABC + D
  2. C + (A + B)D
  3. C + D(A + B)
  4. ABC + BD
  5. C(AB + D)

Answer: C(AB + D)

Question 6 The difference between online and offline PLC programming is . . .

  1. Whether the PLC is running or stopped
  2. Whether the programming PC has internet connectivity
  3. The type of programming cable used
  4. Where the edited program resides
  5. The type of programmer used

Answer: Where the edited program resides

Question 7 In PLC programming, a retentive function is one that:

  1. Defaults to the “on” state
  2. Comes last in the program
  3. Defaults to the “off” state
  4. Cannot be edited or deleted
  5. Is not reset after a power cycle

Answer: Is not reset after a power cycle

Question 8 Normally open contacts are open when:

  1. When Input is not energized
  2. When the input is energized
  3. When input is higher than 20 volts
  4. None of these

Answer: When Input is not energized

Question 9 An OR function implemented in ladder logic uses:

  1. Normally-closed contacts in series
  2. Normally-open contacts in series
  3. A single normally-closed contact
  4. Normally-open contacts in parallel
  5. Normally-closed contacts in parallel

Answer: Normally-open contacts in parallel

Question 10 A good application for a timed interrupt in a PLC program would be:

  1. A communications function block
  2. A PID function block
  3. A math function block
  4. A motor start/stop rung
  5. A “watchdog” timer

Answer: A PID function block

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1. What is PLC ?

PLC stand for “Programmable Logic Controller”. It is a general purpose computer modified specifically to perform control task . It is a hardware device having microprocessor based control system. It is used in industrial automation.

2. What do you mean by PLC scan time?

PLC Scan Time is the time taken by the PLC to read the inputs, solve the Logic, and update the output is called a PLC Scan Time. This time is measured in millisecond .

3. Which is the most popular language in plc programming ?

The most popular language in plc programming is Ladder Logic Diagram.

4. What are the applications of PLC ?

PLC is used in industrial automation. These controllers can automate a specific process, machine function, or even an entire production line.

5. What are components of PLC system ?

There are major 6 components of PLC:
•Processor (CPU)
•Input Module
•Output Module
•Power Supply
•Programming Device/Unit

6. What is ladder diagram ?

Ladder diagram is the most popular programming language used in Plc programming. Ladder diagrams expresses a program as a series of “coils” and “contacts”, simulating the operation of electromechanical relays.
The advantage of ladder diagram is the familiarity many electricians have with the simple operation of relays.


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