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Opto-isolator Question & Answers

January 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
HintThe LEDs are made up of gallium arsenide, and the light-sensitive detector detects the light which is emitted from the LED
2). In optoisolators, which of the following device receives the light?
HintThe light-sensitive devices detects the light which is emitted from the LED and converts that light signals into electrical signals
3). The input LEDs on the optoisolators converts the electrical signal into ________
HintThe light-emitting diodes don't convert the electrical signals into chemical and mechanical signals
4). In PC 817 optoisolator IC the photosensitive element is the ______
HintThe resistors, capacitors, insulators are not photosensitive elements
5). The optoisolators are categorized into ______ types
HintThe phototransistor optocoupler, photodarlington transistor optocoupler, photo Triac optocoupler, and photo SCR based optocoupler
6). Which one of the following is a photo transistor-based optocoupler?
HintThe 4N32, 4N33 are not photo transistor-based optocouplers
7). Which one of the following is a photodarlington transistor-based optocoupler?
HintThe H21B2, H21B3, 4N32, 4N33, H21B1 are photodarlington transistor-based optocouplers
8). Which one of the following is an example for photo SCR-based optocoupler?
HintThe H21B1, 4N32, 4N33 are photodarlington transistor-based optocouplers
9). The MOC3071 is an example for ______ optocoupler
HintMOC3071, MOC3072, IL400, etc are a few examples of photo SCR based optocoupler
10). The optocouplers are used in high power _______
HintThe optocouplers widely used in DC and AC converters
11). Which one of the following optocouplers is designed for triggering TRIACs?
HintThe PC816, 4N32, 4N33 optocouplers designed for other purposes
12). The input current of 6N139 optocoupler is around _____________ mA
HintThe input current is not more than 0.5mA for the 6N139 optocoupler
13). Which one of the following is a placement-based electrical isolator?
HintThe single break type isolator is an application-based electrical isolator
14). Which one of the following isolators connects directly to the main bus?
HintThe transfer bus isolator connects directly to the transfer bus
15). Which one of the following is a unidirectional device?
HintThe TRIAC and DIAC are bidirectional devices
16). Which one of the following is a controlled device?
HintThe DIAC is an uncontrolled device
17). The firing angle of silicon controlled rectifier is from _____________
HintThe firing angle of silicon controlled rectifier is from 0 to 1800
18). The pantograph, knee, double break, centre break, etc are the type of ______________
HintThe vacuum circuit breaker, SF6 circuit breaker, and oil circuit breaker are some types of circuit breakers
19). Which one of the following can be used to re-route the power?
HintThe circuit breakers can't be used to re-route the power
20). Which one of the following isolators connects directly to the transfer bus?
HintThe bus side isolator connects directly to the main bus
21). The frequency range of klystron microwave vacuum tube is ______
HintThe klystron microwave vacuum tube range is from a few GHz to 100 GHz
22). The output power of klystron microwave vacuum tube is ______
HintThe klystron microwave vacuum tube output power is not more than 10MW
23). The efficiency of the klystron microwave vacuum tube is less than ______
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?
HintThe field is stationary in a klystron microwave vacuum tube
25). The vaccum circuit beaker, SF6 circuit beaker, and oil circuit beaker are some type of ______________
HintThe pantograph, knee, double break, center break, etc are the type of isolators or disconnectors

Optoisolator MCQs for Quiz

26). Which one of the following is a part of the relay?
HintThe contacts, spring, and coil are the parts of relays
27). What is the standard form of TRIAC?
HintIt is a type of diode
28). Which one of the following have the main contact, moving blades, and has less thermal capabilities?
HintThe thermal capabilities are better in-circuit breaker
29).The input current of HCPL-4701 optocoupler is around _____________ mA
HintThe input current is not more than 0.5mA for the HCPL-4701 optocoupler
30). Which one of the following is used in choppers, inverters, and rectifiers?
HintThe TRIAC and DIAC are not used in choppers, inverters, and rectifiers
31). What is the standard form of DIAC?
HintIt is a type of diode
32). Which one of the following has two terminals?
HintThe triode alternating current have three terminals
33). Which one of the following is a bi-directional device?
HintThe both DIAC and TRIAC are bi-directional devices
34). Which one of the following is an uncontrolled device?
HintThe triode for alternating current is a controlled device
35). What are the advantages of optocouplers?
HintThe optocouplers works very fast, less noise, low cost, less weight, and compact
36). The electrical isolators are categorized into __________________ types
HintThe electrical isolators are categorized into two types they are application based and placement based
Read more about Isolators
37). Which one of the following is an application-based electrical isolator?
HintThe bus side and transfer bus side are placement-based electrical isolator
38). Which one of the following can't be used to re-route the power?
HintThe isolators can be used to re-route the power
39). The emitter collector voltage of PC817 IC optocoupler is around _______________
HintThe emitter-collector voltage is 6V and the collector-emitter voltage of the PC817 IC optocoupler is around 80V
40). Which one of the following can operate automatically?
HintThe isolator can't operate automatically
41). Which one of the following has the main contact, arcing contacts, and has better thermal capabilities?
HintIn an isolator, the thermal capabilities are less
42).The input current of HCNR200 optocoupler is around _____________ mA
HintThe input current is not more than 10mA for the HCNR200 optocoupler
43). The transistor in a photo transistor is __________________ type of transistor
HintEither NPN or PNP can be used in phot transistor optocoupler
44). Which one of the following optocouplers has two transistors?
HintThe phototransistor, photo SCR, and the photo TRIAC uses only one transistor
Read more about Transistors
45). What are the disadvantages of optocouplers?
HintIt works fast and it is not expensive
46). Which one of the following has three terminals?
HintThe diode alternating current has two terminals
47). The collector current of the PC817 IC optocoupler is around _______________
HintThe collector current value is not more than 50mW in the PC817 integrated circuit optocoupler
48). Which one of the following figures is a photo TRIAC circuit?
Optocouplers
HintBoth photo TRIAC and photo SCR uses to control the AC circuits
49). Which one of the following is an on-load device?
HintThe isolator is an off-load device, which means it can operate only when the power supply is in off mode
50). The collector power dissipation of the PC817 IC optocoupler is around _______________
HintThe collector power dissipation value is not more than 150mW in the PC817 integrated circuit optocoupler

Optoisolator MCQs for Interviews

51).The collector emitter voltage of the PC817 IC optocoupler is around _______________
HintThe emitter-collector voltage is 6V and the collector-emitter voltage of the PC817 IC optocoupler is around 80V
52). The power handling capacity is high in _______________ for alternating current
HintThe power handling capacity is low in diode for alternating current
53). The firing angle of diode for alternating current is ________________
HintThe triode for alternating current will have a firing angle but DIAC doesn't have any firing angle
54). Which one of the following was used to trigger TRIAC?
HintThe TRIAC used in light dimmer, fan control, and many more
55).The input current of the 4N49 optocoupler is around _____________ mA
HintThe input current is not more than 1mA for the 4N49 optocoupler
56). The insulation thickness of the Broadcom optocoupler is from ________________
HintThe thickness of insulation is not more than 2mm
57). Which one of the following is a controlled device?
HintThe diode for alternating current is an uncontrolled device
58). The power dissipation of the PC817 IC optocoupler is around _______________
HintThe power dissipation of the PC817 IC optocoupler is not more than 70mW
59). Which one of the following is an off-load device?
HintThe circuit breaker is an on-load device means it can operate when the power supply is in on or in off mode
60). The total power dissipation of the PC817 IC optocoupler is around _______________
HintThe total power dissipation value is not more than 200mW in the PC817 integrated circuit optocoupler
61). Which one of the following figures is a photo SCR circuit?
Optocouplers
HintBoth photo TRIAC and photo SCR uses to control the AC circuits
62).The insulation thickness of magnetic optocoupler is up to ________________ for single coil
HintThe thickness of insulation is not more than 1mm
63). Which one of the following cannot be used as a circulator?
HintThe circulator can be used as an isolator by terminating one port
64).The reverse voltage of the PC817 IC optocoupler is around _______________
HintThe reverse voltage of the PC817 IC optocoupler is not more than 6V
65). The optocouplers are used in ____________ circuits
HintIt is also used for ground isolation
66). The TRIAC used in __________________ circuits
HintThe TRIAC used in AC power control, high power lamp switching, and also in control circuits
67). Which one of the following figures is a symbol for thyristor?
Diodes Symbols
HintFigures (b) and (c) are the DIAC and TRIAC symbols
68). The application-based electrical isolator is categorized into _______________
HintThe single break type isolator, double break type, pantograph, and MCB isolators are types of application-based electrical isolators
69). What are the applications of DIAC?
HintThe DIAC can be used in speed control of the universal motor, heater control circuit, TRIAC triggering circuit, etc
70).The insulation thickness of capacitive coupler is upto ________________ for single coil
HintThe thickness of insulation is not more than 1mm
71). What are the advantages of silicon control rectifiers?
HintThe SCR has a high switching speed, higher efficiency, and it is small in size
72). The silicon control rectifiers can be used in _________________ circuits
HintThe silicon control rectifiers can be used in power-switching circuits, zero voltage switching circuits, inverters, etc
73). Which one of the following devices works even when the avalanche breakdown occurs?
HintThe TRIAC device will not work when the avalanche breakdown occurs
74). The placement based electrical isolator is categorized into _______________
HintThe bus side, transfer bus side, and the line side isolators are types of placement based isolators
75). The firing angle of triode for alternating current is ________________
HintThe firing angle of triode for alternating current is 0 to 180 and 180 to 360 degrees

Optoisolator MCQs for Exams

76). The power handling capacity is low in _______________ for alternating current
HintThe power handling capacity is high in triode for alternating current
77). Which one of the following figures is a photodarlington circuit?
Optocouplers
HintBoth photodarlington and phototransistors uses in DC circuits
78).The insulation thickness of the capacitive coupler is up to ________________ for double coil
HintThe thickness of insulation is not more than 1mm
79). The maximum rating of Triac device is ____________
HintThe maximum rating is can't be more than 20KW
80). How many electrodes do thyristors consist of?
HintIt is a type of semiconductor device
81). The power diodes are __________________ layer devices
HintThe power transistors are three-layer devices
82). Which one of the following is a three-port device?
HintThe isolator is a two-port device
83).The insulation thickness of the magnetic coupler is up to ________________ for double coil
HintThe thickness of insulation is not more than 1mm
84). Which one of the following figures is a symbol for DIAC?
Diodes Symbols
HintFigure (a) and (c) is the thyristor and TRIAC symbols
85). Which one of the following is a three-layer device?
HintThe power diodes and thyristors are two-layer and four-layer devices
86). What is the standard form of GTO?
HintThe Gate Turnoff Thyristor comes under the thyristor family
87). What is the standard form of SITH?
HintThe Static Induction Thyristor comes under the thyristor family
88). What are the pin names of the PC817 IC optocoupler?
HintThe PC817 IC optocoupler doesn't have a base pin
89). The forward current of the PC817 IC optocoupler is around _______________
HintThe forward current of the PC817 IC optocoupler is not more than 50mA
90). The figure shown below is a pin diagram of __________________
Pin Diagram
HintThe figure shown in the above figure is MOC3031M Zero cross Triac driver pin diagram
91). What is the standard form of MCT?
HintThe MOS Controlled Switch comes under the thyristor family
92). Which one of the following is a four-layer device?
HintThe power diodes and power transistors are two-layer and three-layer devices
93). Which one of the following figures is a phototransistor circuit?
Optocouplers
HintBoth photodarlington and phototransistors uses in DC circuits
94). Which one of the following is a two-port device?
HintThe circulator is a three-port device
95). Which one of the following figures is a symbol for TRIAC?
Diodes Symbols
HintFigure (a) and (b) are the thyristor and DIAC symbols
96).The peak forward current of the PC817 IC optocoupler is around _______________
HintThe peak forward current of the PC817 IC optocoupler is not more than 1A
97). What is the standard form of LASCR?
HintThe Light-Activated Thyristor comes under the thyristor family
98). The gate firing signals are categorized into __________
HintThe DC signals, pulse signals, and AC signals are the basic type of gate firing signals
99). How many pins does PC817 IC have?
HintThe emitter, collector, anode, and cathode are the pin names
100). What is the standard form of SUS?
HintThe Silicon Unilateral Switch comes under the thyristor family
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