Load QuizSave Quiz Welcome to CBT Exam Preparation - Electrician (2nd Year) Try to repeatedly answer the questions till you get the CORRECT answers LET'S CONTINUE 1. Which resistor is used to measure light intensity? VDR NTC PTC LDR 2. Which code indicates silicon semiconductor diode? OA 79 BY 126 IN 4007 2N 3055 3. Which is a active component? Inductor Resistor Capacitor Transistor 4. Which letter indicates the compound material cadmium sulphide? ‘A’ ‘B’ ‘C’ ‘R’ 5. Which system the wick feed lubrication is catagorized? Hand feed Force feed Splash feed Gravity feed | 6. What is the input ripple frequency (Fin) of full wave rectifier? 7. Which letter indicates the compound material cadmium sulphide? A B C R 8. Which is a active component ? Inductor Resistor Capasitor Transitor 9. What is the name of the symbol? Add description here! Two input OR gate Two input AND gate Two input NOR gate Two input NAND gate 10. Which is a passive component? Diac Diode Transitor Capacitor 11. What is the name of the device symbol? ! SCR IGBT DIAC TRIAC 12. How many characters are in hexadecimal number system? 6 8 12 16 13. Which electronic circuit generates A.C signal without input? Filter circuit Rectifier circuit Amplifier circuit Oscillator circuit 14. Which instrument provides a visual representation of measured or tested quantities? Voltage stabilizer Function generator Cathode ray oscilloscope Radio frequency generator 15. What is the name of amplifier? Common emitter amplifier Class B push pull amplifier Common collector amplifier Class AB push pull amplifier 16. What is the minimum voltage required in the base emitter junction to conduct a silicon transistor? 0.2 V – 0.3 V 0.4 V – 0.5 V 0.6 V – 0.7 V 0.8 V – 0.9 V 17. What is the minimum and maximum value of resistor with four colour bands, red, violet, orange and gold respectively? 23750Ω - 26250Ω 24700Ω - 27300Ω 25650Ω - 28350Ω 22400Ω - 33600Ω 18. What is the reason for barrier voltage is more in silicon material? Lower atomic number Resistance is very low Doping percentage is more Valance electrons are two only 19. What is the reason for widened barrier in a reverse biased diode? Minority carriers in two materials are neutralised Electron in N material is drifted to positive terminal Holes in P material attracted to negative terminal Electrons and holes are attracted towards supply terminals 20. What is the output voltage in the full wave rectifier circuit? No output Rated output Half the rated output Double the rated output 21. Which filter circuit is capable of removing voltage spikes in the rectifier circuit? LC filter RC filter Capacitor input filter Series inductor filter 22. Which is the advanced version of power electronic component used in the output stage in drives? FET UJT SCR IGBT 23. How the decimal number can be converted into binary number? Divide decimal by 4 Multiplying decimal by 4 Dividing decimal by 2 Multiplying decimal by 2 24. What is the purpose of using binary coded decimal (BCD) system in digital circuits? Storing the data inputs Control the binary system Interface to binary system Segregating the input parameters 25. Which logic gate refers the truth table? OR gate NOT gate AND gate NOR gate 26. What is the function of R1 variable resistor? Controls the current in R2 Protects from overload to TRIAC Protects the RFI filter from overloading Controls the pulse rate for triggering the TRIAC 27. What is the purpose of connecting L1 through C1 to the transistor base? | Provides DC supply Provides positive feed back Provides negative feedback Provides transistor biasing voltage 28. What is the criteria to decide a material as conductor, semi conductor and insulator? Atomic bonding structure of atom Existence of valance electrons in atom Atomic weight of the atom of the material Atomic number of the atom of the material 29. Which doping material is used to make P-type semi conductor? | Boron Arsenic Antimony Phosphorous 30. Which type of biasing is required to a NPN transistor for amplification? Base ground, emitter and collector positive Base negative, emitter positive and collector negative Base positive, emitter negative and collector positive Base positive, emitter negative and collector negative 31. What is the type of function in the transistor circuit? Switching Oscillation Modulation Amplification 32. Why negative feedback is required in amplifier circuits? To reduce the distortion To increase the amplification factor To increase the output voltage gain To increase the output current gain 33. What is the purpose of DIAC in power control circuits? As rectifier For triggering As an oscillator For amplification 34. Which type of control device is used in electronic fan regulator control circuits? FET UJT DIAC TRIAC 35. Which quadrant operation of SCR delivers heavy current in reverse biasing? First quadrant Third quadrant Fourth quadrant Second quadrant 36. Which logic gate refers the truth table? AND NOT NOR NAND 37. What is the use of time-base control switch or knob in the CRO? Select sweep speed Select input voltage range Select input signal voltage Select intensity of the beam 38. Why a snubber circuit is used in the TRIAC motor control circuit? To avoid false triggering To increase the life of TRIAC To increase the motor torque To maintain the motor speed constant 39. What is the output DC voltage in half wave rectifier, if the input AC voltage is 24 volt? 24 volt 12 volt 9.6 volt 10.8 volt 40. Why most of semi conductor devices are made by silicon compared to germanium? High barrier voltage High resistance range High thermal conductivity High current carrying capacity 41. What is the output voltage if the centre tap of transformer is open circuited in a full wave rectifier circuit? Zero voltage Full rated output Half of the rated output One fourth of rated output 42. Which oscillator provides high accurate stable frequency? Hartley oscillator Colpitts oscillator Quartz crystal oscillator R.C phase shift oscillator 43. What is the characteristic property of base material in a transistor? Lightly doped and very thin | Heavily doped and very thin Lightly doped and very larger Heavily doped and very larger 44. What is the type of amplifier? Push Pull Amplifier Common Base Amplifier Emitter Follower Amplifier Common Emitter Amplifier 45. Which resistor determines the voltage gain in a common emitter amplifier? 46. Which multi vibrator produces a repetitive pulse wave form output? Astable multi vibrator Bistable multi vibrator One shot multi vibrator Monostable multi vibrator 47. Why a feedback network is used in the oscillator? To cancel noise distortion To phase shift the signal by 60 degree To phase shift the signal by 180° To cancel second harmonic distortion 48. What is the main application of a Field Effect Transistor (FET)? Voltage control device Current control device Positive feedback device Low input impedance device 49. What is the main function of Uni Junction Transistor (UJT)? Relaxation oscillator Broadcast transmitter Loud speaker amplifier Microphone input device 50. How the gate terminal of N channel JFET biased? Gates are reverse biased Gates are forward biased Gates are forward biased with drain Gates are reverse biased with source 51. What is the total turn-on time (ton) while transistor makes a transition from V2 to V1? 52. Which device is made up of using the methods of point contact, grown, diffusion and alloy junctions? Inductor Resistor Capacitor Transitor 53. Why the collector region is physically made larger than emitter region in a transistor? It has to dissipate more heat Output taken from collector terminal Base collector region is reverse biased Collector region always operate with high voltage 54. What is the function of a transistor if emitter to base and collector to base are forward biased? Acts as an amplifier Acts as an oscillator Acts as an open circuit Acts as an closed switch. 55. What is the main advantage of a class A amplifier? Minimum distortion Maximum current gain Maximum voltage gain Minimum signal to noise ratio losses 56. Which electronic circuit produces signal waves or pulses without an input? Detector Amplifier Oscillator Modulator 57. Which circuit is essential to maintain oscillations or waves in an oscillator circuit? Rectifier with filter Voltage multiplier Negative feed back Positive feed back 58. What is the main application of uni junction transistor? Rectification Amplification Regulator circuits Triggering circuit 59. Which device has very high input impedance, low noise output, good linearity and low inter electrode capacity? NPN transistor | PNP transistor Field effect transistor Uni junction transistor 60. What is the difference in current control of MOSFET compared to JFETs? Insulating layer instead of junction Using N material instead of P material Using P material instead of N material Using N material gate instead of P material 61. What is the type of amplifier circuit? Common base amplifier Common emitter amplifier Class B push pull amplifier Common collector amplifier 62. What is the peak voltage of 220V rms AC voltage? 310.02 V 311.17 V 312.25 V 315.20 V 63. How the input impedance of CRO can be increased? By adding resistance to CRO probe By adding resistance to trigger level circuit By increasing time/base attenuator switch position By increasing volts/cm attenuator switch position 64. What is the frequency of the displayed signal on CRO screen covered by 5 division with a time base setting of 0.2 micro seconds? 1.0 KHz 10.0 KHz 100.0 KHz 1000.0 KHz 65. What defect will occur in the radio, if the pulsations are not removed from the input of the rectifier? Improper tuning no response Humming sound Works with low volume 66. How does the depletion region behave? As resistor As insulator As conductor As semi conductor 67. What is the power gain of CE amplifier with a voltage gain of 66 and (Beta) of the transistor is 100? 1.5 166 0.66 6600 68. What is the effect, if SCR is latched into conduction and gate current is removed in DC? SCR gets cut off Current through SCR OFF Output voltage will be reduced Gate looses control over conduction 69. What is the effect of pinch-off voltage in JFET? No depletion region exists Drain current becomes zero Reverse bias voltage becomes zero Width of channel has maximum value 70. Which supply indicates by the colour of conductor exihibited on Red, Blue and Black? Supply DC 3 wire system Single phase AC system Supply AC system 3 phase Apparatus AC system 3 phase 71. Which cable ties are used to bunch the wires? Silk ties P.V.C ties Nylon ties Cotton ties 72. Which device is avoided in the panel board assembly? Sensors Indicating lamp Isolating switch Push button switch 73. What is the name of the device marked X’? Stop button Start button Main contact Auxillary contact 74. What is the name of the wiring accessory used in control panel wiring? DIN rails G channel Grommets Race ways 75. What is the name of the device marked as X’ in the cricuit? Contactor No volt coil Stop button Over load relay trip 76. What is the name of the accessory used in control panel wiring? Wire ferrules B Wire sleeves Nylon cable ties cable binding strap 77. What is the name of the accessory used in control panel wiring? Lugs Thimble Grommet Terminal connector 78. Which device protects from overload and short circuit in a panel board? Isolating switch Time delay relay Thermal overload relay Miniature circuit breaker 79. Which switch with an actuator is operated by the motion of a machine or part of an object? Limit switch Toggle switch Isolating switch Push button switch 80. Which switch is operated at OFF load condition? Limit switch Isolating switch Two way switch Push button switch 81. What is the reason for providing two separate Earthing in panel board? Panel board is made in metal box Control the stray field in the pane Reduce the voltage drop in panel board Ensure one earthing in case of other failure 82. Which circuit, the limit switches are used? Lift circuits Street lighting Motor control circuits Domestic power circuits 83. How the control circuit voltage and power in a contactor are to be selected? As per rated current As per supply voltage As per no volt coil rating As per the type of supply 84. What is the criteria to select the contactor? Type of supply Type of load connected Supply voltage and load Place of use the contactor 85. Which accessory is used to mount MCB,OLR in the panel board without using screws? DIN Rail G.Channel Grommets PVC channel 86. Which type of device protects motors from over heating and over loading in a panel board? Rectifier Limit switch Thermal relay Electro mechanical relay 87. 88. What is the use of G’ channels in control panel? For fixing relays For fixing contactors For fixing instruments For fixing terminal connector 89. What is the function of limit switch in control panel wiring? Controls machine from over heat Controls machine from over speed Controls machine from over loading Controls distance movement of any machine 90. Which is the standard duty cycle code of the contactor for starting and stopping the AC resistive and inductive load? AC1 AC2 AC3 AC4 91. Which is the correct sequence operation of contactors for operating automatic star delta strarter? Main-Star-Delta-Timer Star- Main-Timer-Delta Main-Timer-Delta-Star Star-Timer-Main-Delta 92. Why control panels are provided with control transformer? To maintain rated voltage to load To operate the auxiliary circuits To maintain rated main supply voltage To supply reduced voltage to power circuit 93. What happens, if time delay relay of a auto star delta starter still in closed condition after starting? Starts and stop Runs normally Runs in star only Runs in delta only 94. What is the use of PVC channel in a control panel wiring? Mounting MCB Mounting relays Path way for electrical wiring and protection Mounting double deck terminal contactor 95. What is the purpose of thermal over load relay in control panel? Add description here! Switching ON/OFF the circuit Protect the circuit from earth fault Control the circuit based on time delay Protect the motor from over heating and loading 96. Why sequential control of motors is required in an industrial application? | To share more loads To reduce power consumption To minimise the operating cost To increase the accuracy of operation 97. Which material is used to make open frame bimetallic adjustable thermostat contacts? Silver Brass Copper Bronze 98. What is the purpose of DIN-rail used in control panel wiring? It provides a path way for electrical wiring Install the high powered circuit accessories Mounting the double deck terminal connectors Mounting the control accessories without screws 99. Which device controls the operations in sequential control systems? Timer Relays Contactor Control transformer 100. Which DC load is represented by the DC4 standard duty cycle of contactors? Resistive loads except motor loads Starting and stopping of shunt motor starting and stopping of series motor Starting and stopping with inching and braking 101. What is the purpose of control transformer used in control panel wiring? | To maintain constant terminal voltage To supply the power to the auxiliary circuits To control the supply voltage to the contactor To protect the control elements from over voltage fault 102. How the contacts in a contactor can be engaged for working? By manual operation By mechanical settings By operating electromagnet to change the position By using bimetallic strip to change the position 103. Which device prevents flare out of stripped and stranded cables in the panel board? Sleeves Wire ferrules Lugs and thimbles Cable binding straps and button 104. How to protect the cable from insects and rats into the panel? By using sleeve By using Grommets By using cable binding straps By providing nylon cable ties 105. What essential feature to be considered while designing a layout of control panel? Proper type of protection and measuring system Inside area and number of indicating lights in front panel Suitable method of labelling and cable harnessing Outside dimensions and swing area of cabinet door 106. Why power and control wirings run in separate race ways? To reduce heat To reduce the radio interference To increase the insulation resistance To increase the current carrying capacity 107. Why the motor is not changing the direction, if reverse push button is pressed in forward and reverse control star delta starter? No volt coil is not energized Fault in forward contactor Due to interlock in reverse contactor No voltage exist in reverse contactor 108. Which control system consumes very low power for motion control in AC and DC motors? Field control Drives control Voltage control Armature control 109. 110. Which drive is classified according to mode of operation? Group drive Manual drive Individual drive Continuous duty drive 111. 112. What is the name of the characteristic curve in D.C drive? Add description here! Speed Vs torque characteristic Torque Vs field current characteristic | Speed Vs armature current characteristic Field current Vs armature current characteristic 113. 114. 115. What is the name of the component marked as X’ in the block diagram of AC drive? Add description here! Rectifier D.C bus Inverter A.C motor 116. What is electric drive? A device used as prime mover for generator A device converts A.C to D.C supply An electro mechanical device for controlling motor A machine converts mechanical energy into electrical 117. What is the full form of B.O.P in D.C drive? Bridge Operation Panel Basic Operational Panel Basic Operation Programme Bridge Operator Programme 118. Which is the classification of drive according to dynamics and transients? Short time duty drive Intermittent duty drive Automatic control drive Variable position control drive 119. What is the function of power controller in drive circuits? It sounds an alarm in no load conditions It detects the overloading condition of motor It reduce motor current during transient operation It maintain the torque at low voltage conditions 120. Why it is necessary to keep V/F ratio constant in a drive? Keep the stator flux maximum Maintain the rotor current minimum Maintain the speed of motor constant Maintain the rated torque at all speeds 121. Which power modulator used in the electric drive system? Cyclo converters Frequency multiplier Phase sequence indicator Servo controlled voltage stabilizer 122. Which type of sensing unit employed in drive system? Opto coupler Speed sensing Photo voltaic cell Resistance temperature detector 123. Which type of machine in industries is provided with multi motor electric drive? Rolling machine Air Compressor Shearing machine Heavy duty electric drilling machine 124. Which control system is used for Eddy current drives? Slip controller Rectifier controller AC voltage controller DC chopper controller 125. What is the purpose of JOG key in control panel of D.C drive? Stop the motor Restart the motor Inching operation Reverse the direction of motor 126. What is the purpose of LCD on basic operator panel in D.C drive? Indicate the fault Display the speed Monitor the parameter Display availability of supply 127. What is the reason of keeping binding wire gap too close and very tight in pin insulator? Avoid sparking Avoid corrosion Avoid oxide formation Avoid atmospheric pressure 128. Which type of line insulator is used for terminating on corner post? Pin insulator Strain insulator Shackle insulator Suspension insulator 129. Which type of A.C transmission is universally adopted? Two phase four wire Two phase three wire Single phase two wire Three phase three wire 130. What is the reason of using shielded cable for connecting low level signal circuits in DC drives? Easy for connection Good appearance Protects from mechanical injuries Eliminates the electrical interference 131. Which device controls the speed of A.C motor in A.C drive? Field supply unit (FSU) COMMS technology box Speed feedback technology box Microprocessor based electronic device 132. What is the main use of A.C drive? High starting torque Group drive motors Control stepless speed in motors Interlocking system in industries 133. What is the function of IGBT in AC drive? Smoothening incoming A.C supply Controls the power delivered to the motor Stabilize the output voltage from the rectifier Converts incoming A.C power into D.C power output 134. Why the A.C drives are better suited for high speed operation? High starting torque Robust in construction Having lighter gauge winding No brushes and commutation 135. What is the advantage of AC drive compared to DC drive? Requires less space Installation and running cost is less Fast response and wide speed range of control Power circuit and control circuits are simple 136. Which is the application of single quadrant loads operating in first quadrant in drives? Hoists Elevators Conveyors Centrifugal pumps 137. What is the function of Field Supply Unit (FSU) in DC drive? Produces required firing current to the firing circuit Provides variable voltage to the field winding of motor Provides a constant voltage to the field winding of motor Provides a constant voltage to the armature of the motor 138. What is the disadvantage of DC drive? Not suitable for high speed operation More complex with a single power conversion More expensive than AC drive for high capacity motor Installation of DC drives is more complicated 139. What is the purpose of LCD in Basic Operator Panel (BOP) in AC drive? Indicate the status of drive Monitor the parameter of AC drive Indicate the display error in reading Indicate the incorrect operation of BOP 140. Which is the correct sequence operation of key button in BOP of AC drive to change the direction of rotation? Press ON -- REV--ON Press OFF -- REV -- ON Press ON --OFF --REV --ON Press ON --REV --OFF --ON 141. What is the purpose of PROG / DATA button in BOP of AC drive? To change the parameter setting To store the entered data and factory stored data To display the data direction of rotation forward / REV To display the data status of frequency and current 142. Which is proportional to the torque in D.C motor? Back e.m.f Field current Terminal voltage Armature current 143. What is IGBT in VF drive? Inverter switching device D.C bus switching device Rectifier switching device Field supply switching device 144. What is the function of VSI drives? Converts A.C to D.C Converts A.C to A.C Converts D.C to A.C Converts D.C to D.C
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