Silicon Controlled Rectifiers Question & Answers September 1, 2021 By Wat Electrical Leave a Comment This article lists 100 Silicon Controlled Rectifiers MCQs for Engineering Students. All the Silicon Controlled Rectifiers Questions & Answers given below includes solution and link wherever possible to the relevant topic. Silicon Controlled Rectifiers also represented as SCR is a semiconductor diode operating in a single direction. It was invented in the year 1957 by Tanenbaum at Bell labs. The purpose of designing an SCR is to control high voltage applications. An SCR is fabricated with four layers namely p-n-p-n, forming 3 junctions J1, J2, and J3 consisting of 3 main terminals, input, and output terminals that include Anode, Cathode terminal, and a gate terminal. The operation of SCR in forward bias and reverse bias depends on the quantity of voltage applied at the gate. It operates in three modes namely forward blocking mode (off state), forward conduction mode (on state), and reverse blocking mode (off state). The process of turning on an SCR is called triggering. This can be achieved by 5 processes that include forward type voltage triggering, light triggering, dv/dt triggering, and temperature-based triggering. The process of turning off SCR is called Commutating, this can be achieved using Class A, ClassB, ClassC, Class D, Class E type SCR’s. SCR benefits in terms of handling high voltage, protect from short circuits, and can control power to load. Applications of an SCR circuit are lamp dimmers, power-based regulators, and motors. 1). A silicon controlled rectifier (SCR) is designed with _____ material. Conducting Insulating Semi-conducting Both a and b None Hint 2). How many layers is SCR designed with? 2 3 4 5 None Hint 3). Who developed SCR? Tanenbaum Moll Goldey All the above None Hint 4). SCR is a ___ component. Active Passive Electromechanical None of the above None Hint 5). How many pins does an SCR consist of ? 2 3 4 5 None Hint 6). Which of the following is a charge representation for cathode in SCR? + - * / None Hint 7). Which of the following is a charge representation for anode in SCR? + - * / None Hint 8). How many junctions does SCR diode have? 2 3 4 5 None Hint 9). SCR is also known as ______. Thyristor Resistor Capacitor Jammer None Hint 10). An SCR operates in ____ number of directions. Uni Bi Tri Any None Hint 11). What is the charge applied on SCR’s gates terminal to make it operate? +ve – ve No charge Both a and b None Hint 12). In how many modes does an SCR operate? 2 3 4 5 None Hint 13). Which of the following is the off state mode of SCR? Forward blocking mode Forward conduction mode Reverse blocking mode Both a and c None Hint 14). Which of the following is the on state mode of SCR? Forward blocking mode Forward conduction mode Reverse blocking mode Both a and c None Hint 15). What is the charge applied to anode of SCR during forward type blocking mode? +ve –ve No charge Both a and b None Hint 16). What is the charge applied to cathode of SCR during forward type blocking mode? +ve –ve No charge Both a and b None Hint 17). What is the charge applied to the gate of SCR during forward type blocking mode? +ve –ve No charge Both a and b None Hint 18). Which of the following junctions of an SCR conducts in forward bias in forward blocking type mode? J1 J2 J3 Both a and c None Hint 19). Which of the following junctions of an SCR conducts in reverse bias in forward blocking type mode? J1 J2 J3 Both a and c None Hint 20). How much leakage current flows through J2 of SCR in forward blocking type mode? Small Large Zero Both a and b None Hint 21). Which of the following junction of SCR in forward blocking type mode goes into Avalanche breakdown when the junction reaches maximum limit? J1 J2 J3 Both a and c None Hint 22). Which of the following junction of SCR in forward blocking type mode starts conducting after avalanche break down? J1 J2 J3 Both a and c None Hint 23). How many conditions are present to turn on SCR from blocking to conducting mode? 2 3 4 5 None Hint 24). How much quantity of latching current is required for a SCR in forward conduction mode to maintain in On state? Minimum Maximum Continuous Zero None Hint 25). How much quantity of current is required for a SCR in forward conduction mode to OFF SCR? Minimum Maximum Below min Zero None Hint Silicon Controlled Rectifiers MCQs for Interviews 26). What is the charge applied on SCR’s anode terminal to make it operate in an reverse type blocking mode? +ve – ve No charge Both a and b None Hint 27). What is the charge applied on SCR’s cathode terminal to make it operate in an reverse type blocking mode? +ve – ve No charge Both a and b None Hint 28). Which of the following junctions of an SCR conducts in reverse bias in reverse blocking type mode? J1 J2 J3 Both a and c None Hint 29). Which of the following junctions of an SCR conducts in forward bias in reverse blocking type mode? J1 J2 J3 Both a and c None Hint 30). At what junctions is avalanche breakdown observed for an SCR operating in reverse blocking type mode? J1 J2 J3 Both a and c None Hint 31). What is the value of voltage type blocking rate for reverse and forward SCR? 0 Infinity Same Ranges between -2 to +2 None Hint 32). How many methods an SCR has to turn on? 5 4 3 2 None Hint 33). Which of the following is the method that turns on SCR when cathode and anode is applied with increasing forward voltage and gate is open circuited? Light based triggering Temperature based triggering Gate based triggering Forward voltage based triggering. None Hint 34). Which of the following is the method that turns on SCR when depletion region’s width reduces as increase in temperature? Light based triggering Temperature based triggering Gate based triggering Forward voltage based triggering. None Hint 35). Which of the following are the applications of an SCR circuit? Lamp dimmers Power based regulators Motors All the above None Hint 36). Which of the following are the methods used for turning of an SCR diode? Natural type commutation Forced type commutation Badged type commutation Both a and b None Hint 37). In to how many classes do a forced type commutation is divided into? 4 3 5 6 None Hint 38). Which of the following class of commutation is self commutated with resonating load in an SCR? Class A Class B Class C Class D None Hint 39). Which of the following class of commutation is self commutated with LC based circuit in an SCR? Class A Class B Class C Class D None Hint 40). Which of the following class of commutation is Cor based LC type switched using other load SCR? Class A Class B Class C Class D None Hint 41). Which of the following class of commutation is LC or C type switched using auxiliary based SCR? Class A Class B Class C Class D None Hint 42). Which of the following class of SCR commutation is an external based pulse source? Class A Class E Class C Class D None Hint 43). Which of the following are the characteristics of a natural based commutation of SCR thyristor? Employs AC voltage No external components are required Zero cost All the above None Hint 44). Which of the following are the characteristics of a forced based commutation of SCR thyristor? Employs DC voltage External components are required Has effective cost All the above None Hint 45). _______ is called as the process to operate a thyristor. Triggering Commutation Loading Stepping None Hint 46). ______ is called as the process to off a thyristor. Triggering Commutation Loading Stepping None Hint 47). What is the equation of peak current for an Class B type thyristor? ipeak = V [ sqroot (C/L)] ipeak = V ipeak = V [C/L] ipeak = [C/L] None Hint 48). What happens in Class A type SCR when current is passed through anode? Inductance gets heated up Capacitor gets charged up Forms a under type damped circuit of LCR Both b and c None Hint 49). At what condition does an SCR stops operating in Class A? When C charges up When C begins to charge When inductor starts to flow Both a and c None Hint 50). Up to what condition SCR operates in reverse bias type condition in Class A? Until voltage of capacitor and supply voltage are equal Until supply voltage is is greater than capacitor voltage Until capacitor voltage is greater than supply voltage Unitl capacitor discharges all its charge None Hint Silicon Controlled Rectifiers Exam Questions & Answers 51). Up to what condition does a capacitor charges in Class B type SCR? Until maximum gate voltage is applied Before voltage is supplied to gate Before avalanche breakdown None of the above None Hint Read more about Capacitor. 52). How many component does an class B SCR have on supplying gate voltage? 2 3 4 5 None Hint 53). What is value of current flowing through Class B type SCE in a RL load? Higher Lower Constant Zero None Hint 54). What is the value of Inductance when constant value of current flows through load in Class B SCR? Large Small Zero Equal None Hint 55). How is load connected in Class B type SCR with respect to reactance? Parallel Series Concurrent Both a and c None Hint 56). Which type of wave pass through LC circuit in Class B SCR? Square Sinusoidal Rectangle Both a and c None Hint 57). What is the value of reverse type current with respect to load type current to turn off Class B type SCR? Greater Smaller Equal Zero None Hint 58). What is the value of re-applied based voltage and rated based value of Class B SCR? Greater Smaller Equal Zero None Hint 59). How many SCR's does Class C type SCR have? 2 3 4 5 None Hint 60). Which of the following component is used in an class E type SCR to block saturation? Transformer Load Capacitor All the above None Hint Read more about Transformer. 61). What is the value of voltage drop of a transformer in Class E SCR when it carries load current to other components in circuit? Small Large Very high Zero None Hint 62). On which of the following factors an SCR is selected for an application? RMS Peak cycle based surge on current value Gate based trigger voltage All the above None Hint 63). When an SCR hits break over voltage, it further results in raise in critical based rate of voltage of an cathode and anode. This statement is defined as ___ condition of SCR. Latching Dropout RMS Holding current None Hint 64). Which of the following is the SCR condition, when current is minimized until either one or all the transistors enter cutoff mode? Latching Dropout RMS Holding current None Hint 65). An SCR acts like ______ type of component. Thyristor Shockley type diode Zenor type diode Both a and b None Hint 66). What is the value of current applied to one complete cycle in an SCR without disturbing its performance according to peak cycle based surge on current parameter? Minimum Maximum Zero Infinity None Hint 67). An SCR in DC type motor has _______ number of SCR’s. 1 2 3 4 None Hint Read more about DC Motors. 68). During positive cycle of motor operation how many SCR operate in forward bias? 1 2 3 4 None Hint 69). During negative cycle of motor operation how many SCR operate in forward bias? 1 2 3 4 None Hint 70). Which of the following are different types of SCR’s? BT151 TYN608 2P4M All the above None Hint 71). How many pins does an discrete type plastic SCR package has? 2 3 4 1 None Hint 72). What is the capacity of discrete type plastic SCR package? 25 A, 1000V 30A, 100V 30A, 1000V 10A, 1000V None Hint 73). What is the capacity of plastic type module SCR package? Up to 10Amps Up to 100Amps 10 Amps 2 Amps None Hint 74). Which of the following are the characteristics of a stud type SCR? Has screwed base Easily mounted Less thermal resistance All the above None Hint 75). What is the capacity of stud type SCR? 5 to 150A Full voltage range Zero resistance Both a and b None Hint Silicon Controlled Rectifiers MCQs With Answers 76). Which of the following is the disadvantage provided by stud type SCR? Cannot be separated from heat sink Breaks down easily High cost Consumes more power None Hint 77). Which of the following is the advantage of flat base type SCR? Uses insulation Partitions from heat sink Low cost Both a and b None Hint 78). What is the capacity of flat base type SCR? 10 to 400 Amp 20 AMPS 30 Amps 1000 AMPs None Hint 79). What is the capacity of press pack type SCR? Greater than 200Amp Above 100 Amp 50 AMP 10 Amp None Hint 80). Asymmetrical type SCR’s are also named as ________. Reverse based conducting thyristors Forward based conducting thyristors Semi conducting based thyristors Both a and b None Hint 81). Which of the following is the function of an asymmetrical type SCR? Blocking reverse based voltage Cannot block reverse based voltage Cannot block reverse based current Blocks reverse based current None Hint 82). How much reverse type breakdown ratings does an ASCR have? 10’s of volts 100’s of volts 1000’s of volts Milli voltage None Hint 83). Which of the following are the applications of a RSCR? Diode Inverters Frequency changers Both b and c None Hint Read more about Inverters. 84). On comparing SCR with SCS switch, which one turns off when positive voltage is given to its anode? SCR SCS ASCR Both a and b None Hint 85). Which of the following are the applications of an SCS? Lamp drivers Logic circuits Counters All the above None Hint 86). Which of the following switch is specifically used in AC type applications? SCR ASCR TRIAC None of the above None Hint 87). Which of the following are the applications of TRIAC? AC power based switching AC motor based control circuits Light dimming circuits All the above None Hint Read more about Electronic Light Dimmer Circuits Using TRIAC. 88). Which of the following are examples of semiconducting materials? Silicon Germanium Gallium Arsenide All the above None Hint 89). What are the +ve charge carriers of semiconductors? Holes Electrons Neutrons None of the above None Hint 90). What are the -ve charge carriers of semiconductors? Holes Electrons Neutrons None of the above None Hint 91). Which of the following semiconducting charge carriers have both positive and negative? Holes Electrons Neutrons None of the above None Hint 92). To form a p-type type semi conductor which of the following charge carriers are doped? Holes Electrons Neutrons Both a and b None Hint 93). To form a n-type type semi conductor which of the following charge carriers are doped? Holes Electrons Neutrons Both a and b None Hint 94). Holes charge carriers are also known as ______. Donors Acceptors Receptors Both b and c None Hint 94). N-type charge carriers are also known as ______. Donors Acceptors Receptors Both b and c None Hint 95). Which of the following are the elements of n-type semi conductor? Antimony Arsenic Phosphorous All the above None Hint 96). Which of the following are the elements of p-type semi conductors? Gallium Aluminum Boron All the above None Hint 97). An Shockley diode has ______ number of layers. 2 3 4 5 None Hint 98). Which of the following is the primary characteristic of a Shockley diode? Negative based resistance Positive based resistance Both a and b High resistance None Hint 99). Who invented Shockley diode? William James William Shockley John H None of the above None Hint 100). Which of the following are the components of a Shockley diode? Anode Cathode Gate Both a and b None Hint Time's up
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