Opto-isolator Question & AnswersJanuary 3, 2022 By WatElectronics This article lists 100 Opto-isolator MCQs for Engineering Students. All the Opto-isolators Questions & Answers given below includes solution and link wherever possible to the relevant topic.Opto-isolators are integrated electronic components, they are also known as optical isolators, Opto-couplers, and photocouplers. It is used to block high voltages and transfers the data across the isolation barrier by using LEDs and photo-sensitive transistors. It is useful whenever we want to provide electrical isolation between the two circuits, and with the electrical isolation, it is even possible to avoid the ground loops. The PC 817 and 4N25 are very well-known general-purpose optocouplers.The optoisolators consist of light-emitting diodes and light-sensitive devices. The LEDs are made up of gallium arsenide, and the light-sensitive detector detects the light which is emitted from the LED and converts that light signal into electrical signals. The phototransistor, photodarlington transistor, photo Triac, and photo SCR-based optoisolator are the four types of optoisolators and these optoisolators are used in high power choppers, inverters, AC converters, DC converters, light control circuits, dimmer circuits, etc.The isolator is an off-loading device, which means it can operate only when the power supply is in off mode. The single break type isolator, double break type, pantograph, and MCB isolators are types of application-based electrical isolators.1). The optoisolator consists of _______ devices LEDs Light-sensitive detector Both a and b None of the above HintThe LEDs are made up of gallium arsenide, and the light-sensitive detector detects the light which is emitted from the LED2). In optoisolators, which of the following device receives the light? LEDs Light sensitive device Both a and b None of the above HintThe light-sensitive devices detects the light which is emitted from the LED and converts that light signals into electrical signals3). The input LEDs on the optoisolators converts the electrical signal into ________ Chemical Mechanical Light None of the above HintThe light-emitting diodes don't convert the electrical signals into chemical and mechanical signals4). In PC 817 optoisolator IC the photosensitive element is the ______ Resistor Capacitor Phototransistor Insulator HintThe resistors, capacitors, insulators are not photosensitive elements5). The optoisolators are categorized into ______ types One Two Four Six HintThe phototransistor optocoupler, photodarlington transistor optocoupler, photo Triac optocoupler, and photo SCR based optocoupler6). Which one of the following is a photo transistor-based optocoupler? PC816 4N32 4N33 Both b and c HintThe 4N32, 4N33 are not photo transistor-based optocouplers7). Which one of the following is a photodarlington transistor-based optocoupler? H21B1 4N32 4N33 All of the above HintThe H21B2, H21B3, 4N32, 4N33, H21B1 are photodarlington transistor-based optocouplers8). Which one of the following is an example for photo SCR-based optocoupler? H21B1 4N32 4N33 IL420 HintThe H21B1, 4N32, 4N33 are photodarlington transistor-based optocouplers9). The MOC3071 is an example for ______ optocoupler Photo transistor-based Photo Darlington transistor Photo SCR based None of the above HintMOC3071, MOC3072, IL400, etc are a few examples of photo SCR based optocoupler10). The optocouplers are used in high power _______ Inverters Choppers Both a and b None of the above HintThe optocouplers widely used in DC and AC converters11). Which one of the following optocouplers is designed for triggering TRIACs? PC816 4N32 4N33 Moc3021 HintThe PC816, 4N32, 4N33 optocouplers designed for other purposes12). The input current of 6N139 optocoupler is around _____________ mA 0.5mA 1mA 2mA 3mA HintThe input current is not more than 0.5mA for the 6N139 optocoupler13). Which one of the following is a placement-based electrical isolator? Single break type isolator Bus side isolator Transfer bus side isolator Both b and c HintThe single break type isolator is an application-based electrical isolator14). Which one of the following isolators connects directly to the main bus? Bus Transfer bus Lineside None of the above HintThe transfer bus isolator connects directly to the transfer bus15). Which one of the following is a unidirectional device? DIAC TRIAC SCR None of the above HintThe TRIAC and DIAC are bidirectional devices16). Which one of the following is a controlled device? DIAC TRIAC SCR Both b and c HintThe DIAC is an uncontrolled device17). The firing angle of silicon controlled rectifier is from _____________ 0 to 1800 1800 to 3600 Both a and b None of the above HintThe firing angle of silicon controlled rectifier is from 0 to 180018). The pantograph, knee, double break, centre break, etc are the type of ______________ Circuit breakers Isolators Both a and b None of the above HintThe vacuum circuit breaker, SF6 circuit breaker, and oil circuit breaker are some types of circuit breakers19). Which one of the following can be used to re-route the power? Circuit breakers Isolators Both a and b None of the above HintThe circuit breakers can't be used to re-route the power20). Which one of the following isolators connects directly to the transfer bus? Bus Transfer bus Lineside None of the above HintThe bus side isolator connects directly to the main bus21). The frequency range of klystron microwave vacuum tube is ______ 1.4GHz Few GHz to 100 GHz 1GHz 32GHz HintThe klystron microwave vacuum tube range is from a few GHz to 100 GHz22). The output power of klystron microwave vacuum tube is ______ 10MW 20MW 30MW 40MW HintThe klystron microwave vacuum tube output power is not more than 10MW23). The efficiency of the klystron microwave vacuum tube is less than ______ 90% 10% 60% 70% HintThe efficiency is more than 10% in other microwave vacuum tubes but in klystron, it is less than 10%24). In which one of the following tubes does the field travels along with the beam? Klystron Traveling wave tube Both a and b None of the above HintThe field is stationary in a klystron microwave vacuum tube25). The vaccum circuit beaker, SF6 circuit beaker, and oil circuit beaker are some type of ______________ Circuit breakers Isolators Both a and b None of the above HintThe pantograph, knee, double break, center break, etc are the type of isolators or disconnectorsOptoisolator MCQs for Quiz26). Which one of the following is a part of the relay? Contacts Spring Coil All of the above HintThe contacts, spring, and coil are the parts of relays27). What is the standard form of TRIAC? Triode for Alternating Current Triode for Analog Current Triode for Alternating Controller None of the above HintIt is a type of diode28). Which one of the following have the main contact, moving blades, and has less thermal capabilities? Circuit breaker Isolator Both a and b None of the above HintThe thermal capabilities are better in-circuit breaker29).The input current of HCPL-4701 optocoupler is around _____________ mA 0.04mA 1mA 2mA 3mA HintThe input current is not more than 0.5mA for the HCPL-4701 optocoupler30). Which one of the following is used in choppers, inverters, and rectifiers? DIAC TRIAC SCR Both b and c HintThe TRIAC and DIAC are not used in choppers, inverters, and rectifiers31). What is the standard form of DIAC? Digital Analog Current Diode Analog Current Diode Alternating Current None of the above HintIt is a type of diode32). Which one of the following has two terminals? DIAC TRIAC Both a and b None of the above HintThe triode alternating current have three terminals33). Which one of the following is a bi-directional device? DIAC TRIAC Both a and b None of the above HintThe both DIAC and TRIAC are bi-directional devices34). Which one of the following is an uncontrolled device? DIAC TRIAC Both a and b None of the above HintThe triode for alternating current is a controlled device35). What are the advantages of optocouplers? Works very fast Less noise Low cost, less weight, and compact All of the above HintThe optocouplers works very fast, less noise, low cost, less weight, and compact36). The electrical isolators are categorized into __________________ types Two Four Six Seven HintThe electrical isolators are categorized into two types they are application based and placement based Read more about Isolators37). Which one of the following is an application-based electrical isolator? Single break type isolator Bus side isolator Transfer bus side isolator None of the above HintThe bus side and transfer bus side are placement-based electrical isolator38). Which one of the following can't be used to re-route the power? Circuit breakers Isolators Both a and b None of the above HintThe isolators can be used to re-route the power39). The emitter collector voltage of PC817 IC optocoupler is around _______________ 10V 20V 6V 80V HintThe emitter-collector voltage is 6V and the collector-emitter voltage of the PC817 IC optocoupler is around 80V40). Which one of the following can operate automatically? Circuit breaker Isolator Both a and b None of the above HintThe isolator can't operate automatically41). Which one of the following has the main contact, arcing contacts, and has better thermal capabilities? Circuit breaker Isolator Both a and b None of the above HintIn an isolator, the thermal capabilities are less42).The input current of HCNR200 optocoupler is around _____________ mA 0.04mA 1mA 2mA 0.1-10mA HintThe input current is not more than 10mA for the HCNR200 optocoupler43). The transistor in a photo transistor is __________________ type of transistor NPN PNP Both a and b None of the above HintEither NPN or PNP can be used in phot transistor optocoupler44). Which one of the following optocouplers has two transistors? Phototransistor Photo Darlington Photo SCR Photo TRIAC HintThe phototransistor, photo SCR, and the photo TRIAC uses only one transistor Read more about Transistors45). What are the disadvantages of optocouplers? Low cost Works very fast Not handle high current None of the above HintIt works fast and it is not expensive46). Which one of the following has three terminals? DIAC TRIAC Both a and b None of the above HintThe diode alternating current has two terminals47). The collector current of the PC817 IC optocoupler is around _______________ 80mW 90mW 70mW 50mW HintThe collector current value is not more than 50mW in the PC817 integrated circuit optocoupler48). Which one of the following figures is a photo TRIAC circuit? Figure 1 Figure 2 Figure 3 Figure 4 HintBoth photo TRIAC and photo SCR uses to control the AC circuits49). Which one of the following is an on-load device? Circuit breaker Isolator Both a and b None of the above HintThe isolator is an off-load device, which means it can operate only when the power supply is in off mode50). The collector power dissipation of the PC817 IC optocoupler is around _______________ 80mW 90mW 70mW 150mW HintThe collector power dissipation value is not more than 150mW in the PC817 integrated circuit optocouplerOptoisolator MCQs for Interviews51).The collector emitter voltage of the PC817 IC optocoupler is around _______________ 10V 20V 60V 80V HintThe emitter-collector voltage is 6V and the collector-emitter voltage of the PC817 IC optocoupler is around 80V52). The power handling capacity is high in _______________ for alternating current Diode Triode Both a and b None of the above HintThe power handling capacity is low in diode for alternating current53). The firing angle of diode for alternating current is ________________ 0 to 180 180 to 360 Both a and b None of the above HintThe triode for alternating current will have a firing angle but DIAC doesn't have any firing angle54). Which one of the following was used to trigger TRIAC? DIAC TRIAC Both a and b None of the above HintThe TRIAC used in light dimmer, fan control, and many more55).The input current of the 4N49 optocoupler is around _____________ mA 0.04mA 1mA 2mA 0.1-10mA HintThe input current is not more than 1mA for the 4N49 optocoupler56). The insulation thickness of the Broadcom optocoupler is from ________________ 0.08mm to 2mm 0.08mm to 3mm 0.08mm to 4mm 0.08mm to 5mm HintThe thickness of insulation is not more than 2mm57). Which one of the following is a controlled device? DIAC TRIAC Both a and b None of the above HintThe diode for alternating current is an uncontrolled device58). The power dissipation of the PC817 IC optocoupler is around _______________ 100mW 70mW 80mW 90mW HintThe power dissipation of the PC817 IC optocoupler is not more than 70mW59). Which one of the following is an off-load device? Circuit breaker Isolator Both a and b None of the above HintThe circuit breaker is an on-load device means it can operate when the power supply is in on or in off mode60). The total power dissipation of the PC817 IC optocoupler is around _______________ 80mW 90mW 70mW 200mW HintThe total power dissipation value is not more than 200mW in the PC817 integrated circuit optocoupler61). Which one of the following figures is a photo SCR circuit? Figure 1 Figure 2 Figure 3 Figure 4 HintBoth photo TRIAC and photo SCR uses to control the AC circuits62).The insulation thickness of magnetic optocoupler is up to ________________ for single coil 0.08mm to 2mm 0.02mm 0.08mm to 4mm 0.08mm to 5mm HintThe thickness of insulation is not more than 1mm63). Which one of the following cannot be used as a circulator? Isolator Circulator Both a and b None of the above HintThe circulator can be used as an isolator by terminating one port64).The reverse voltage of the PC817 IC optocoupler is around _______________ 6V 7V 8V 9V HintThe reverse voltage of the PC817 IC optocoupler is not more than 6V65). The optocouplers are used in ____________ circuits Light control Dimmer High voltage monitoring All of the above HintIt is also used for ground isolation66). The TRIAC used in __________________ circuits Control AC power control High power lamp switching All of the above HintThe TRIAC used in AC power control, high power lamp switching, and also in control circuits67). Which one of the following figures is a symbol for thyristor? Figure (a) Figure (b) Figure (c) None of the above HintFigures (b) and (c) are the DIAC and TRIAC symbols68). The application-based electrical isolator is categorized into _______________ Two Three Four Six HintThe single break type isolator, double break type, pantograph, and MCB isolators are types of application-based electrical isolators69). What are the applications of DIAC? Used in speed control Used in the heater control Used in TRIAC triggering All of the above HintThe DIAC can be used in speed control of the universal motor, heater control circuit, TRIAC triggering circuit, etc70).The insulation thickness of capacitive coupler is upto ________________ for single coil 0.08mm to 2mm 0.014mm 0.08mm to 4mm 0.08mm to 5mm HintThe thickness of insulation is not more than 1mm71). What are the advantages of silicon control rectifiers? HIgh switching speed Small in size Higher efficiency All of the above HintThe SCR has a high switching speed, higher efficiency, and it is small in size72). The silicon control rectifiers can be used in _________________ circuits Power switching Zero voltage switching Inverters All of the above HintThe silicon control rectifiers can be used in power-switching circuits, zero voltage switching circuits, inverters, etc73). Which one of the following devices works even when the avalanche breakdown occurs? TRIAC DIAC Both a and b None of the above HintThe TRIAC device will not work when the avalanche breakdown occurs74). The placement based electrical isolator is categorized into _______________ Three Three Four Six HintThe bus side, transfer bus side, and the line side isolators are types of placement based isolators75). The firing angle of triode for alternating current is ________________ 0 to 180 180 to 360 Both a and b None of the above HintThe firing angle of triode for alternating current is 0 to 180 and 180 to 360 degreesOptoisolator MCQs for Exams76). The power handling capacity is low in _______________ for alternating current Diode Triode Both a and b None of the above HintThe power handling capacity is high in triode for alternating current77). Which one of the following figures is a photodarlington circuit? Figure 1 Figure 2 Figure 3 Figure 4 HintBoth photodarlington and phototransistors uses in DC circuits78).The insulation thickness of the capacitive coupler is up to ________________ for double coil 0.08mm to 2mm 0.014mm 0.08mm to 4mm 0.028mm HintThe thickness of insulation is not more than 1mm79). The maximum rating of Triac device is ____________ 20KW 30KW 50KW 16KW HintThe maximum rating is can't be more than 20KW80). How many electrodes do thyristors consist of? One Two Three Four HintIt is a type of semiconductor device81). The power diodes are __________________ layer devices One Two Three Four HintThe power transistors are three-layer devices82). Which one of the following is a three-port device? Isolator Circulator Both a and b None of the above HintThe isolator is a two-port device83).The insulation thickness of the magnetic coupler is up to ________________ for double coil 0.08mm to 2mm 0.04mm 0.08mm to 4mm 0.028mm HintThe thickness of insulation is not more than 1mm84). Which one of the following figures is a symbol for DIAC? Figure (a) Figure (b) Figure (c) None of the above HintFigure (a) and (c) is the thyristor and TRIAC symbols85). Which one of the following is a three-layer device? Power diodes Power transistors Thyristors All of the above HintThe power diodes and thyristors are two-layer and four-layer devices86). What is the standard form of GTO? Gate Turnoff Thyristor Gate Thyristor Turnon Gate Thyristor Turnoff None of the above HintThe Gate Turnoff Thyristor comes under the thyristor family87). What is the standard form of SITH? Static Induction Transistor Static Induction Thyristor Static Induction Transformer None of the above HintThe Static Induction Thyristor comes under the thyristor family88). What are the pin names of the PC817 IC optocoupler? Anode, cathode, emitter, base Anode, cathode, emitter, collector Anode, cathode, collector, base None of the above HintThe PC817 IC optocoupler doesn't have a base pin89). The forward current of the PC817 IC optocoupler is around _______________ 60mA 70mA 80mA 50mA HintThe forward current of the PC817 IC optocoupler is not more than 50mA90). The figure shown below is a pin diagram of __________________ Zero cross Triac driver SCR output optocoupler Photovoltaic optocoupler None of the above HintThe figure shown in the above figure is MOC3031M Zero cross Triac driver pin diagram91). What is the standard form of MCT? Metal Controlled Switch Mass Controlled Switch Main Controlled Switch MOS Controlled Switch HintThe MOS Controlled Switch comes under the thyristor family92). Which one of the following is a four-layer device? Power diodes Power transistors Thyristors All of the above HintThe power diodes and power transistors are two-layer and three-layer devices93). Which one of the following figures is a phototransistor circuit? Figure 1 Figure 2 Figure 3 Figure 4 HintBoth photodarlington and phototransistors uses in DC circuits94). Which one of the following is a two-port device? Isolator Circulator Both a and b None of the above HintThe circulator is a three-port device95). Which one of the following figures is a symbol for TRIAC? Figure (a) Figure (b) Figure (c) None of the above HintFigure (a) and (b) are the thyristor and DIAC symbols96).The peak forward current of the PC817 IC optocoupler is around _______________ 6A 7A 1A 5A HintThe peak forward current of the PC817 IC optocoupler is not more than 1A97). What is the standard form of LASCR? Light-Activated Transistor Light-Activated Transformer Light-Activated Thyristor None of the above HintThe Light-Activated Thyristor comes under the thyristor family98). The gate firing signals are categorized into __________ One Two Three Four HintThe DC signals, pulse signals, and AC signals are the basic type of gate firing signals99). How many pins does PC817 IC have? Two Three Four Six HintThe emitter, collector, anode, and cathode are the pin names100). What is the standard form of SUS? Static Unilateral Transistor Static Unilateral Switch Silicon Unilateral Switch None of the above HintThe Silicon Unilateral Switch comes under the thyristor family Time is Up! 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