Free PLC Hardware & Architecture Questions and Answers

Question 1

What is the primary function of a PLC's CPU module?

Accepted Answer

Executing control programs and processing data

Answer

Providing power to input modules

Answer

Directly connecting to field devices

Answer

Storing long-term historical data

Question 2

Which component interfaces with physical field devices in a PLC system?

Accepted Answer

Input/Output (I/O) modules

Answer

Power supply unit

Answer

Communication module

Answer

Programming terminal

Question 3

What is the purpose of a PLC's backplane?

Accepted Answer

To interconnect all system components

Answer

To store backup programs

Answer

To provide physical mounting for modules only

Answer

To display system status

Question 4

Which memory type retains data during power loss in a PLC?

Accepted Answer

EEPROM

Answer

RAM

Answer

DRAM

Answer

Cache memory

Question 5

What is the typical voltage range for PLC digital input modules?

Accepted Answer

24VDC (10-30V range)

Answer

5-12VDC

Answer

120VAC

Answer

480VAC

Question 6

Which communication protocol is commonly used for PLC-to-PLC communication?

Accepted Answer

Modbus RTU/TCP

Answer

HTTP

Answer

FTP

Answer

Bluetooth

Question 7

What is the function of a PLC's watchdog timer?

Accepted Answer

To detect and recover from CPU faults

Answer

To measure process duration

Answer

To synchronize I/O updates

Answer

To schedule maintenance

Question 8

Which component provides isolation between field devices and PLC electronics?

Accepted Answer

Opto-isolators

Answer

Relay contacts

Answer

Capacitors

Answer

Resistors

Question 9

What determines a PLC's scan time?

Accepted Answer

Program size and system configuration

Answer

Only the CPU clock speed

Answer

The color of the PLC housing

Answer

Ambient temperature only