PLC Question & Answers June 21, 2021 By WatElectronics This article lists 50+ PLC MCQs for engineering students. All the PLC Questions & Answers given below include a solution and link wherever possible to the relevant topic. A programmable logic controller or PLC is simply a special type of computer. It is composed of three components they are input, CPU, and output. Suppose we want to control an electric motor using a push-button by turning ON/OFF, this function is similar to the power button on the TV remote. To do this, we must write a program for this operation on a computer and then download that into the CPU. The switch button is connected to the input and the output is connected to the motor, now if we press the button an electrical signal is sent to the PLC, then the PLC input will deliver the signal to the CPU and the CPU process the data received and sent the result to the output, then the output turns the data to a raw electrical signal and applies that to the motor to run. The PLC is extensively used in manufacturing and automation. Its purpose is to monitor crucial process parameters and to adjust process operation accordingly. The input module, output module, CPU, and power supply are the components that make the programmable logic controller work. It is classified into two types they are fixed PLC and modular PLC. In fixed programmable logic controller both input and output modules are fixed whereas in modular PLC the input and output modules are not fixed. The programmable logic controllers can be programmed in ladder logic, structured text, instruction list, functional block diagram, and sequential function chart. In modular PLC the input and output modules are expandable whereas in fixed programmable logic controllers both input and output modules are fixed. 1). The programmable logic controllers are used in __________ Manufacturing Automation Both a and b None of the above None Hint 2). What are the components that make the programmable logic controller work? Input and output module CPU Power supply All of the above None Hint 3). The programmable logic controller is classified into ___________ One Two Three Four None Hint 4). In fixed programmable logic controller _______ Input is fixed Output is fixed Both a and b None of the above None Hint 5). The PLC’s can be programmed in _______ Ladder logic, structured text Instruction list, Functional block diagram Sequential function chart All of the above None Hint 6). In modular programmable logic controller _______ Input is fixed Output is fixed Both a and b None of the above None Hint 7). What are the types of programmable logic controllers? Fixed, uniform PLC Modular, uniform PLC Fixed and Modular PLC None of the above None Hint 8). The components that make PLC works can be divided into ____________ core areas One Two Three Four None Hint 9). How many operation steps does the programmable logic controller have? One Two Three Four None Hint 10). In PLC operation ___________ checks the status at the input side Input scan Output scan Program scan None of the above None Hint 11). In PLC operation ___________ retrieves the data into an output module Input scan Output scan Program scan None of the above None Hint 12). Before PLC’s was created many industries used _________ Relays Capacitors Resistors None of the above None Hint 13). Which is the first PLC model? PLC 084 PLC 085 PLC 086 None of the above None Hint 14). The relays consist of __________ Control circuit Load circuit Both a and b None of the above None Hint 15). CCTV cameras is an example for ________ automation Building automation Office automation Scientific automation Industrial automation None Hint 16). The control logic in a programmable logic controller can be programmed by _____ FBD , ladder logic Sequential logic Structured text All of the above None Hint PLC MCQs for Quiz 17). Who invented the Programmable Logic Controller (PLC)? Jonas Wenstrom Dick Morley Thomas Davenport None of the above None Hint 18). The programmable logic controllers are used in __________ Glass and paper industry Process automation plants Cement manufacturing All of the above None Hint 19). In modular type PLC, the PLC’s are classified into _______ Relay output PLC Transistor output PLC Triac output PLC All of the above None Hint 20). The programmable logic controllers are classified into _________ according to physical size in modular type PLC Mini PLC, Micro PLC Micro PLC, Nano PLC Nano PLC, Mini PLC, Macro PLC None of the above None Hint 21). The advantages of PLC are ______ Easy maintenance Reliability is high Small in size All of the above None Hint 22). The CPU has ______ Memory system Processor Power supply All of the above None Hint Read more about Control Unit 23). The visual programming language also called as _______ Relay logic Ladder logic Controller logic All of the above None Hint 24). _________ are the components that are required to change or create a program PLC, programming device Programming software Connector cable All of the above None Hint 25). __________ is an example for light automation? Rocket launching Street solar lightening Automated bottle filling stations Smoke detectors None Hint 26). In the water level storage tank, the manual mode program controls the water level by monitoring the _________ switch input Low sensor switch High sensor switch Both a and b None of the above None Hint 27). The sequences are classified into _________ One Two Three Four None Hint 28). __________ is an example for scientific automation? Rocket launching Street solar lightening Automated bottle filling stations Smoke detectors None Hint 29). The PLC internally operates, stores, and calculates the value in _____ Binary format Decimal format Octal format None of the above None Hint 30). The DVP-PLC external input-output points are numbered in _________ format Binary format Decimal format Octal format None of the above None Hint PLC Interview Questions 31). Which one is the correct sequence for PLC operation? Self-test, input scan, logic scan, output scan Self-test, logic scan, output scan, input scan Self-test, input scan, output scan, logic scan None of the above None Hint 32). The electromagnetic relays are constructed with _______ Electrical components Mechanical components Electromechanical components None of the above None Hint 33). The DC and AC relays works on __________ principle Motors Electromagnetic induction Electromechanical components None of the above None Hint 34). The attraction type electromagnetic relays works with _________ AC supply DC supply Both ac and dc supply None of the above None Hint 35). In PLC the user can write the programs with the help of ________ Optical isolation Sensing devices Programming devices None of the above None Hint 36). The system that is used to direct, regulate or command itself Open-loop Close-loop Both A and D Control system None Hint 37). In which control system feedback is available? Open-loop Close-loop Both A and D None of the above None Hint 38). Relays is a ___________ device Electrical devices Electromechanical devices Mechanical devices None of the above None Hint 39). Which one is the PLC programming language? HMI MMI FBD None of the above None Hint 40). The standard form of PLC is ______ Programmable Logic Controller Programmable Load Controller Pressure Load Controller None of the above None Hint Read more about PLC 41). The ladder logic in PLC consists of _________ Logic gates Functional blocks Relay contacts and coils Relays None Hint 42). __________ is an example for office automation? Rocket launching Street solar lightening Automated bottle filling stations Printers, CCTV cameras None Hint 43). The relays operates on __________ Low power Control circuits of very high power Both a and b None of the above None Hint 44). What is the standard form of IEC? International Electrotechnical Commission International Electrical Commission None of the above None Hint 45). Which one is the oldest programming language? Ladder logic Function block diagram Structured text programming None of the above None Hint 46). What are the elements of ladder logic? Normally open (contact) Normally Close (contact) Both a and b None of the above None Hint 47). __________ is an example for building automation? Rocket launching Street solar lightening Automated bottle filling stations Smoke detectors None Hint 48). Relays are used in ________ Washing machines Refrigerators Water heaters All of the above None Hint 49). The standard form of STL is ________ Step Transformer Line Step Ladder Diagram Step Transient Line None of the above None Hint 50). What is the standard form of FBD? Functional Block Diagram First Block Diagram Functional Block Division None of the above None Hint 51). __________ is an example for industrial automation? Rocket launching Street solar lightening Automated bottle filling stations Smoke detectors None Hint 52). What are the components that are used to make relay __________ Electromagnet Spring Armature All of the above None Hint 53). The steel factories is an example for ____________ automation Building automation Office automation Scientific automation Industrial automation None Hint 54). Why programmable logic controllers are required? It reduces the efforts of human begins To get the maximum efficiency To reduce the complex circuitry of entire system All of the above None Hint 55). What is the standard form of MODICON? Main Digital Controller Modular Digital Controller Modular Digital Communication None of the above None Hint 56). Which mode accepts and converts signals from sensors into a logic signal? Input module Output modular Both a and b None of the above None Hint 57). ___________ is an example for input modules in programmable logic controller Switches Pushbuttons Lamps Both a and b None Hint 58). __________ is an example for output modules in the programmable logic controller Switches Alarms Lamps Both b and c None Hint 59). Which is not a graphical programming language for the programmable logic controller? Ladder logic Structures text Functional block diagram Sequential function chart None Hint 60). How many inputs does a unitary programmable logic controller have? 10, 15 15, 20 20-40 20, 12 None Hint 61). How many input and output pins do a small programmable logic controller have? 10 30 50 128 None Hint PLC MCQs with Hints 62). _________ is connected to the PLC input Indicating lamp Field sensors Both a and b None of the above None Hint 63). _________ is the device that can’t be connected to the PLC output Pressure Transmitter Motor Control valve None of the above None Hint 64). The programmable logic controller works on __________ Parallel mechanism Sequential mechanism Both a and b None of the above None Hint 65). How many input and output pins do a nano programmable logic controller have? 16 30 50 128 None Hint 66). How many input and output pins do a micro programmable logic controller have? 32 30 50 128 None Hint 67). ________ can be connected to the analogue output of the programmable logic controller Control valve Level transmitter Flow transmitter None of the above None Hint 68). _________ provides the voltage to PLC primary components Control valve Level transmitter Flow transmitter Power supply None Hint 69). Which type of memory is used in PLC? Random Access Memory Read Only Memory Both a and b None of the above None Hint 70). The CPU consists of _________ Arithmetic Logic Unit Internal memory of CPU Internal timers, counters, flags All of the above None Hint Time's up
