Silicon Controlled Rectifier Question & Answers May 31, 2021 By WatElectronics This article lists 100+ Silicon Controlled Rectifier MCQs for engineering students. All the Silicon Controlled Rectifier Questions & Answers given below include a hint and wherever possible link to the relevant topic. This is helpful for the users who are preparing for their exams, interviews, or professionals who would like to brush up their fundamentals on the Silicon Controlled Rectifier topic. SCR is abbreviated as Silicon controlled rectifier, is a semiconductor device and also called thyristor which includes 4 layers namely p-n-p-n, 3 junctions J1, J2, J3, and 3 terminals namely, anode, cathode, and gate. SCR was invented by Frank W and Gordon Hall and its principle was developed by Goldey, Tanenbaum, Holonyak, and Moll in 1956. These devices are implemented in devices where high voltage and power control are used. It operates in 3 modes as Reverse blocking type mode, Forwards conduction type mode, and Forward blocking type mode. A few of the applications of SCR are a switch battery charger, controls motor speed, and power converters. 1). SCR is abbreviated as _________. Silicon controlled rectifier Silicon conducting rectifier Silicon-controlled resistor None of the above Hint Read more about Silicon Controlled Rectifier. 2). Silicon controlled rectifier (SCR) is also called as _________. Semiconductor controlled rectifier Semiconductor conducting rectifier Semiconductor controlled resistor None of the above Hint 3). SCR has ________ layers. 2 3 4 5 Hint 4). SCR principle was developed by _________. Goldey Holonyak Tanenbaum All the above Hint 5). SCR principle was developed by Goldey, Tanenbaum, Holonyak, and Moll in which year? 1996 1956 1999 2000 Hint 6). SCR principles practical demonstration was presented by which of the following scientist? Dr. Lan M. Mackintosh Goldey Holonyak Tanenbaum Hint 7). SCR is a _______ type of device. Thyristor Resistor Capacitor Diode Hint 8). A thyristor is a _______ type of switch. Monostable Bistable Tri stable Multi stable Hint 9). SCR was invented by which scientist? Gordon Hall Frank W Both a and b Henry Hint 10). SCR has _______ number of terminals. 2 3 4 1 Hint 11). An Anode is _______ polarity. Positive Negative Zero Both a and c Hint 12). A Cathode is ________ polarity. Positive Negative Zero Both a and c Hint 13). SCR has _______ junctions. 2 3 4 5 Hint 14). SCR is _______ directional type device. Multi Uni Bi Mono Hint 15). SCR is a unidirectional type device, means it conducts in a _______ direction. Single direction Multiple direction No direction Bi- direction Hint 16). In how modes can a SCR operate? 2 3 4 5 Hint 17). Which of the following are the modes of SCR? Forward blocking type mode Forward conduction type mode Reverse blocking type mode All the above Hint 18). The 3 modes of SCR can be represented in _______ forms. On sate Off-state Both a and b Zero stage Hint 19). Forward blocking mode is also called as _______ state. On sate Off-state Both a and b Zero stage Hint 20). Forward conduction type mode is also called as _______ state. On state Off-state Both a and b Zero stage Hint 21). Reverse blocking type mode is also called as _______ state. On state Off state Both a and b Zero stage Hint 22). Forward conduction type mode, anode terminal is connected to ______ type voltage source. Positive Negative Zero Ground Hint 23). Forward conduction type mode, cathode terminal is connected to _______ type voltage source. Positive Negative Zero Ground Hint 24). In forward conduction type mode, the gate terminal is connected to ______ type voltage source. Positive Negative Ground Both a and b Hint 25). Which of the following junctions in SCR forward conduction type mode are forward biased? J1 J3 J2 Both a and b Hint Silicon Controlled Rectifier MCQs for Interviews 26). Which of the following junctions in SCR Forward conduction type mode are reverse biased? J1 J3 J2 Both a and b Hint 27). A small leakage current in SCR Forward conduction type mode flows in _______ direction. Anode to cathode Cathode to anode Cathode to ground Anode to ground Hint 28). If input voltage at J2 in SCR Forward conduction type mode increases to break overvalue, then J2 becomes ______. Avalanche breakdown Conducts more Creates resistance All the above Hint 29). Does the J2 in SCR Forward conduction type mode start conducting after avalanche breakdown? Yes No May be Hint Read more about Avalanche Breakdown. 30). What is the resistance of J2 in SCR Forward conduction type mode before avalanche breakdown? High Low Zero Infinite Hint 31). SCR in forward conduction type mode switches from blocking mode type to ______ mode. Conduction Nonconduction Resistance Capacitance Hint 32). SCR in forward conduction type mode, switches from blocking mode type to conduction type mode by applying ______ type of pulses to gate terminal. Positive Negative Zero Both a and b Hint 33). When gate voltage is applied to an SCR in forward conduction type mode does SCR switches its state? Yes No May be Hint 34). The process of passing minimum amount of current to SCR in forward conduction type mode to maintain in ON state is called ___current. Switch Latching Nonlatching Resistive Hint 35). In how many ways can a SCR in forward conduction type mode can be turned off? 2 3 4 5 Hint 36). Which are the 2 ways an SCR in forward conduction type mode can be turned off? Reducing value of current below minimum value Shorting cathode and anode Turning off gate All the above Hint 37). SCR in forward conduction type mode can turned off by reducing value of current below minimum value is called _______. Holding current Resistive Threshold None of the above Hint 38). SCR in the reverse blocking mode type anode is supplied with _______ voltage. Positive Negative Ground All the above Hint 39). SCR in the reverse blocking mode type cathode is supplied with _______ voltage. Positive Negative Ground All the above Hint 40). Which of the following junctions in SCR in reverse blocking mode type are reverse biased? J1 J3 J2 Both a and b Hint 41). J1, J2, J3 is represented as _________ in SCR. Junctions Jammers Both a and b None of the above Hint 42). Which of the following junctions in SCR in forward blocking mode type are reverse biased? J1 J3 J2 Both a and b Hint 43). SCR reverse blocking mode type has _______ number of reverse bias diodes. 1 2 3 4 Hint 44). The amount of leakage current in SCR reverse blocking mode flow is ________. Large Small Zero Infinite Hint 45). When reverse type voltage is increased at a critical breakdown in SCR reverse blocking, the mode is called ______. Reverse breakdown voltage Forward voltage Forward breakdown voltage None of the above Hint 46). Reverse breakdown voltage in SCR reverse blocking mode is represented as ________. VBR VSR VDR VJR Hint 47). Reverse breakdown voltage in SCR reverse blocking mode avalanche occurs at _______ junctions. J1 J2 J3 Both a and c Hint 48). In SCR reverse blocking mode, reverse type current value ________. Increases Decreases Remains Same Hint 49). SCR reverse blocking mode adds up with _______ voltage drop. Reverse Forward Zero Infinite Hint 50). Which of the following is true for SCR reverse blocking mode that adds up with forward type voltage drop? Due to long dope at P1 Due to low dope P1 region Both a and b Zero Hint Silicon Controlled Rectifier Important Questions for Interviews 51). Which of the following is the application of reverse blocking type SCR? Current source inverters Voltage source inverters Both a and b None of the above Hint 52). The process that does not block reverse SCR voltage is called ________. Asymmetrical SCR Symmetrical SCR Both a and b None of the above Hint 53). ASCR in reverse blocking type SCR is abbreviated as __________. Asymmetrical SCR Artificial SCR Artifact SCR None of the above Hint 54). ASCR in reverse blocking type has a ________ breakdown rating. Forward Reverse Zero All the above Hint 55). ASCR in the reverse blocking type has reverse breakdown rating of ________ volts. 100’s 10's 1000’s None of the above Hint 56). ASCR is fabricated with ______ type of conducting diode in reverse blocking type SCR. Reverse Forward Zero None of the above Hint 57). RCT in reverse blocking type SCR is abbreviated as _________. Reverse conducting diode Reverse control diode Reverse conducting device None of the above Hint 58). ________ are also called reverse conducting type thyristor. Reverse conducting diode Reverse control diode Reverse conducting device None of the above Hint 59). How many methods are there to turn on a thyristor? 2 3 4 5 Hint 60). Which of the following are the methods to turn on a thyristor? Gate triggering Forward voltage triggering dv/dt triggering All the above Hint 61). At what condition does forward voltage triggering method in SCR begin? Anode – cathode forward type voltage is raised Gate is opened Both a and b Gate is closed Hint 62). Which junction in the forward voltage triggering method in SCR breaks down? J1 J2 J3 All the above Hint 63). When the J2 junction in forward voltage triggering method in SCR breaks down it is called _______ condition. Reverse bias Forward bias Avalanche breakdown Both a and b Hint 64). At what voltage state in forward voltage triggering method in SCR changes from avalanche breakdown? High Low Sufficient Zero Hint 65). At sufficient voltage state in forward voltage triggering method in SCR changes from avalanche breakdown with _______. Low voltage drop Large forward current Both a and b Large voltage drop Hint 66). Which of the following junctions in forward voltage triggering method in SCR are forward biased? J1 J2 J3 Both a and c Hint 67). Gate triggering in thyristor occurs during ________ blocking state. Forward Reverse Zero All the above Hint 68). Gate triggering in thyristor has gate voltage ______ than breakdown voltage. Greater Less Zero Infinite Hint 69). A condition where the width of the depletion region decreases when temperature rises is called _______. Temperature triggering Forward voltage triggering dv/dt triggering All the above Hint 70). Which junction triggers SCR in the temperature triggering method? J1 J2 J3 J0 Hint 71). SCR circuit contains which of the following components? AC voltage source SCR Resistive load All the above Hint 72). SCR circuit on input side has _________ component. AC voltage source SCR Resistive load All the above Hint 73). SCR circuit on output side has ________ component. AC voltage source SCR Resistive load All the above Hint 74). Initially before applying any pulse to SCR, SCR remains in ________ state. Forward blocking state Reverse blocking state Forward non blocking state Reverse nonblocking state Hint 75). The delay angle in SCR is represented as ________. α Ø Ω A Hint Silicon Controlled Rectifier MCQs With Answers 76). At what condition does SCR turn off? When the current becomes negative When the current becomes positive When the current becomes zero None of the above Hint 77). At what condition is SCR current zero. Stays before a gate current pulse is given Stays on a gate current pulse are given Stays after a gate current pulse is given All the above Hint 78). SCR is applied in the digital devices with ________ properties. High power High voltage Low power Both a and b Hint 79). SCR operation with high voltage and power properties are suitable in which of the following applications? Lamp dimming Power regulators Motor control All the above Hint 80). Which of the following behaves similar to SCR? SCS SCD PNP NPN Hint 81). SCS is abbreviated as _________. Silicon controlled switches Silicon current switches Silicon contact switches None of the above Hint 82). What is the main difference between SCR and SCS? SCS turns off-on positive input voltage applied to anode terminal SCS turns off-on negative input voltage applied to anode terminal SCS turns off-on zero input voltage applied to anode terminal None of the above Hint 83). SCS uses ________ number of control pulses. 1 2 3 0 Hint 84). Which of the following are the applications of SCS? Power switching circuits Lamp drivers Logic circuits All the above Hint 85). TRIAC as SCR acts as ________ controlled switches. Electrically Mechanical Electronic None of the above Hint 86). Which of the following are the home applications of SCR? Heater Fan regulator Temperature controller All the above Hint 87). Which of the following are the industrial applications of SCR? Battery charger Power converters Control motor speed All the above Hint 88). Which of the following is the most important application of SCR? Switch Battery Converter All the above Hint 89). SCR switch circuit contains how many components? 6 5 4 3 Hint 90). Which of the following component does the SCR switch circuit protect the diodes from high voltage? Resistors Switch Wire Load Hint Read more about Diodes. 91). In the SCR switch circuit at what condition current flows through diode and SCR? Switch is closed Switch is open Switch is absent None of the above Hint 92). During positive half cycle in an SCR switch circuit current flows to load via _______. SCR1 Switch SCR2 Load Hint 93). In a negative half cycle of an SCR switch, the circuit SCR2 component is ______ biased. Forward Reverse Zero None of the above Hint 94). In a negative half cycle of an SCR switch, the circuit SCR1 component is _______ biased. Forward Reverse Zero None of the above Hint 95). SCR switch circuit can handle current in the ________ range. Few mill amps to several 100 amps 10amps to 100amps 0 to 10amps 300 amps to 270amps Hint 96). SCR switch circuit benefits which of the following switching branch? Mechanical Electromechanical Electrical Both a and b Hint 97). Can an SCR control the power within the circuit? Yes No Maybe Hint 98). On which factor does SCR in power control applications depend? Load Number of components Type of source used Design factor Hint 99). Which of the following is controlled in SCR AC circuits? Phase Wire Components Connection Hint 100). What is the input given to AC SCR circuit? AC DC Both a and b Zero Hint 101). SCR in AC SCR circuit is connected in _________ fashion. Anti-parallel Series Both a and b Tangentially Hint 102). Which of the following is varied in SCR AC application circuit? Firing angle Load Voltage Supply Hint 103). The advantage of the SCR circuit is __________. Turns off automatically Protects from damage Open circuit Both a and b Hint 104). SCR V-I characteristics is plotted with ___ on X axis and __ on y axis? Ia and Va * Ig Ia and Ig Va and Va * Ig Ia and Va Hint Time is Up! Time's up
