TS ECET EEE 2021

1. The resistance of a copper wire is R ohms. This wire is streched to its double length. The new resistance of the wire in ohms

A. R
B. R/2
C. 4R
D. 2R

Answer : C. 4R
Explanation:-

2. The maximum power that can be transferred to the load Rl connected across the terminals of voltage source of V=10V and internal resistance of 100 Ohm is

A. 0.5W
B. 10W
C. 1W
D. 0.25W

Answer : D. 0.25W
Explanation:-

3. A voltage source 20V, Internal resistance 5ohms is connected in parallel with another voltage source of 10V with internal resistance of 10Ohms. The thevenins voltage of this combination is

A. 30 v
B. 50/3 v
C. 15 v
D. 20 v

Answer : B. 50/3 v
Explanation:-

4. Which of the statements are correct?

A) 1KWH = 3.6M J
B) 1HP(British) = 735.5 W
C) 1HP(Metric) = 746 W
D) 1 Nm = 1J

A. A and B only
B. A and C only
C. C and D only
D. A and D only

Answer :D. A and D only
Explanation:-

5. The power consumed by an immersion heater operating on a 230 V, 50Hz single phase supply is 2.3 Kw. Then the resistance of the heater is

A. 2.3 ohm
B. 23 ohm
C. 46 ohm
D. 4.6 ohm

Answer : B. 23 ohm
Explanation:-

6. Two long single layer solenoids have the same length and the same number of turns but are placed co-axially are within the other. The diameter of the inner coil is 60 mm and that of the outer coil is 75mm. The co-efficient of coupling between the coils is

A. 0.6
B. 0.8
C. 0
D. 1

Answer : B. 0.8
Explanation:-

7. The plates of a parallel plate capacitor are designed to have a cross section of 100 mm2, and they are seperated by a distance of 0.1 mm, with air as dielectric between them. If the capacitor is charged to 100V, how much of energy is stored in it?

A. 8.85 pJ
B. 44.3 mJ
C. 8.85 nJ
D. 44.3 nJ

Answer : D. 44.3 nJ
Explanation:-

8. Which of the following conducting material is used as conductors for overhead transmission lines?

A. Aluminium
B. ACSR
C. CCSR
D. Steel

Answer : B. ACSR
Explanation:-

9. The cathode and anode of a lead acid battery are respectively made up of

A. lead and lead
B. lead peroxide and lead
C. lead oxide and lead
D. lead and lead peroxide

Answer : D. lead and lead peroxide
Explanation:-

10. Which of the following material has highest dielectric strength?

A. Porcelain
B. cotton
C. teflon
D. bakelite

Answer : A. Porcelain
Explanation:-

11. The purpose of using compensating winding in DC generators is to

A. reduce the eddy currents
B. provide a path for cooling air
C. neutralize the effect of cross-magnetisation
D. reduce the hysteresis loss

Answer : C. neutralize the effect of cross-magnetisation
Explanation:-

12. Lap winding is suitable for ___ applications of DC generators

A. high voltage, low current
B. low voltage, low current
C. high volatge, high current
D. low voltage, high current

Answer : D. low voltage, high current
Explanation:-

13. The characteristics which makes shunt generators most suited for stable parallel operation is ____

A. rising voltage
B. drooping voltage
C. identical voltage
D. linear voltage

Answer : B. drooping voltage
Explanation:-

14. If the back emf of a DC motor is 115 V, the supply voltage to develop maximum

A. 230 V
B. 115 V
C. 460 V
D. 57.5 V

Answer : A. 230 V
Explanation:-

15. A 230 V DC S hunt motor takes an armature current of 20A on a aparticular load. The armature resistance is 0.5ohms. The value of resistance required in series with the armature to reduce the speed by 50% is ( assume load torque is constant)

A. 2.5 ohms
B. 3.5 ohms
C. 4.5 ohms
D. 5.5 ohms

Answer : D. 5.5 ohms
Explanation:-

16. A DC shunt motor drives a load torque at rated voltage and rated excitation. If the load torque is doubled, the motor speed would be

A. doubled
B. halved
C. decreased slightly
D. increased slightly

Answer : C. decreased slightly
Explanation:-

17. The moving system of an indicating type of electrical instrument at equilibrium point

A. Deflecting torque is equal to Damping torque
B. Deflecting torque is greater than Damping torque
C. Controlling torque is equal to Damping torque
D. Deflecting torque is equal to Controlling torque

Answer : D. Deflecting torque is equal to Controlling torque
Explanation:-

18. Identify the wrong statement with respect to potential transformer

A. PT Secondary is commonly designed for an output voltage of 110 volts
B. Generally PTs are of shell type
C. secondary of PT must be shirt circuited
D. PT has a small volt-ampere ratings

Answer :C. secondary of PT must be shirt circuited
Explanation:-

19. The maximum measurable voltage by a DC potentiometer is 2V with a slide wire of 800mm length. When it is used to measure the emf the balance is obtained at wire lengths of 600 mm and 680 mm with a standard cell of 1.18 V and a test cell, respectively. Calculate the emf of the test cell?

A. 1.00 V
B. 1.34 V
C. 1.70 V
D. 1.50 V

Answer :B. 1.34 V
Explanation:-

20. Which of the following instruments can measure currents and voltages of very high frequencies uoto about 50MHz

A. Moving iron instruments
B. thermocouple instruments
C. dynamometer type instruments
D. PMMC Instruments

Answer : B. thermocouple instruments
Explanation:-

21. The current is measured by a clamp meter by sensing the _____ around the conductor

A. electric field
B. magnetic field
C. charge
D. electric and magnetic field

Answer : B. magnetic field
Explanation:-

22. An AC Series circuit consisting of a resistance of 6 ohms and an inductive reactance of 8 ohms is connected to a single ohase 200v,50Hz AC supply. The current flowing in the circuit would be

A. 14.3 A
B. 10 A
C. 20 A
D. 25 A

Answer : C. 20 A
Explanation:-

23. Three elements R=1/3 Ohm;L=1/4 Ohm and C=3F are connected in seroes across input voltage,v(t)= sin2t the phase angle difference between supply voltage and current flowing through the circuit is

A. 30
B. 45
C. 60
D. 75

Answer :B. 45
Explanation:-

24. The phase sequence available in a poly phase system are given as YBRYB,BYRBY,BRYBR,RBYRB,RYBRY,YRBYR,RYBRYB,RBYRBY, YBRYBR,YRBYRB,BRYBRY and BYRBYR.How many phase sequences are actually available in it?

A. 9
B. 3
C. 2
D. 6

Answer : C. 2
Explanation:-

25. Identify the correct statement from the following

A. In delta connected 3 phase system, phase current lags behind the respective line current by 30 degrees
B. In delta connected 3 phase system, line current lags behind the respective phase current by 30 degrees
C. In star connected 3 phase system, the phasor sum of all the phase voltages is zero
D. In star connected 3 phase system, line voltage lags behind the respective phase voltage by 30 degrees

Answer : B. In delta connected 3 phase system, line current lags behind the respective phase current by 30 degrees
Explanation:-

26. A transformer exhibits maximum efficiency, when the

A. variable loss = constant loss
B. primary copper loss = secondary copper loss
C. no load iron loss = no load copper loss
D. no load iron loss = full load copper loss

Answer : A. variable loss = constant loss
Explanation:-

27. Generally the no load currnt drawn by a transformer is _____ of the full load current

A. 10 to 15%
B. 2 to 5%
C. 0.2 to 0.5%
D. 20 to 30%

Answer :B. 2 to 5%
Explanation:-

28. Which of the following conditions are not necessary for parallel operation of two, 1-phase transformers that these shoud have
1) same polarity
2) KVA rating
3) efficiency
4) voltage regualtion
5) X/R ratio

A. 1 and 2 only
B. 1 and 4 only
C. 2 and 3 only
D. 2 and 5 only

Answer : C. 2 and 3 only
Explanation:-

29. The full load copper loss of a transformer is 160W, At half full load, the copper loss will be

A. 120W
B. 160W
C. 80W
D. 40W

Answer :D. 40W
Explanation:-

30. Which of the following of the transformers can be determined only from sumpner's test?

A. voltage regulation
B. stray losses
C. temperature rise
D. all day efficiency

Answer : C. temperature rise
Explanation:-

31. Distribution transformers have core losses

A. greater than copper losses
B. equal to copper losses
C. less than copper losses
D. half of the copper losses

Answer : C. less than copper losses
Explanation:-

32. Which of the following 3-phase connection is used for small hv transformers?

A. Delta-Delta
B. Star-Star
C. Delta-Star
D. Star-Delta

Answer : B. Star-Star
Explanation:-

33. A hydraulic turbine with rated speed of 250rpm is driving a synchronous generator. The number of poles for which the generator has to be designed to generate electrical energy at 50Hz is

A. 16
B. 8
C. 12
D. 24

Answer : D. 24
Explanation:-

34. If the excitation is kept constant in an alternator, then the excitation voltage variation with speed would be

A. linear
B. First linear and the horizontal
C. first curved and then linear
D. first linear and then curved upwards

Answer : A. linear
Explanation:-

35. The total number of inputs required to be given to an alternator, for all practical applications is

A. 1
B. 2
C. 3
D. 4

Answer :B. 2
Explanation:-

36. While starting a 3phase synchronous motor, its field winding should be

A. short circuited
B. kept open
C. connected to a dc source
D. connected to an ac source

Answer : A. short circuited
Explanation:-

37. Ignoring the effects of armature reaction, if the excitation of a synchronous motor running on constant load is decreased from its normal value, it results in increase of

A. both the armature current and power factor angle
B. the back emf with a decrease in armature current
C. the armature current with a decrease in power factor angle
D. the torque angle with a decrease in back emf

Answer :A. both the armature current and power factor angle
Explanation:-

38. When the load on a 3phase induction motor is increased from No load to full load

A. both pf anf slip increases
B. both pf anf slip decreases
C. pf increases but slip decreases
D. pf decreases but slip increases

Answer : A. both pf anf slip increases
Explanation:-

39. Placing of rotor copper bars of a 3 phase induction motors deep inside the slots, results in

A. increase of starting torque
B. reduction of copper losses
C. improvement of efficiency
D. increase of power factor

Answer :A. increase of starting torque
Explanation:-

40. Which of the following losses can be obtained during blocked rotor test on a 3phase induction motor?

A. stator core loss
B. rotor core loss
C. friction and windage loss
D. stator and rotor copper loss

Answer : D. stator and rotor copper loss
Explanation:-

41. An induction motor can be run at synchronous speed when

A. an external emf is injected into the rotor circuit
B. it is run in reverse direction
C. it is run on zero direction
D. it is run on voltage higher than the rated voltage

Answer : A. an external emf is injected into the rotor circuit
Explanation:-

42. The motor, best suited for domestic refrigerator is

A. universal motor
B. shaded pole motor
C. capacitor start single phase induction motor
D. 3-phase induction motor

Answer : C. capacitor start single phase induction motor
Explanation:-

43. A power plant consumes 3600 tons of coal per day. If the coal ha an average energy content of 10000 Btu/lb. Assume 15% efficiency. The plany output in MW is

A. 200
B. 232
C. 132
D. 100

Answer : C. 132
Explanation:-

44. Two generating stations A and B have the same consumers connected. However customer behaviour is different when connected to them. In such a case, If plant A and B have diversity factors of 2 and 1.5 respectively, then

A. Plant A installed capacity is larger than Plant B installed capacity
B. Plant B installed capacity is larger than Plant A installed capacity
C. Plant A and B have the same installed capacities
D. diversity factor has no effect with plant installed capacity.

Answer : B. Plant B installed capacity is larger than Plant A installed capacity
Explanation:-

45. The coolant water in a pressurised water reactor is

A. boiled in the reactor core
B. pressurised to work as moderator
C. used for controlling the chain reaction
D. pressurised to prevent water from boiling in the core

Answer : D. pressurised to prevent water from boiling in the core
Explanation:-

46. A hydel plant supplied by a river with a discharge 3000 m3/sec at a head of 30m, with a plant efficiency of

A. 697.50 MW
B. 342.20 MW
C. 823.70 MW
D. 423.12 MW

Answer : A. 697.50 MW
Explanation:-

47. Out of the following electric power generating plants, which one is renewable and non-intermittent in nature?

A. wind power plant
B. solar PV power plant
C. ocean wave energy power plant
D. Hydroelectric power plant

Answer : D. Hydroelectric power plant
Explanation:-

48. Resistance switching is normally used in

A. Air blast circuit breaker
B. oil circuit breaker
C. SF6 circuit breaker
D. Vacuum circuit breaker

Answer : A. Air blast circuit breaker
Explanation:-

49. The rate of rise of restriking voltage (RRRV), on opening across the circuit breaker contacts will mainly depend on

A. the type of circuit breaker used
B. the line parameters RLC
C. The type of fault or disturbance happened
D. the contact material used

Answer :B. the line parameters RLC
Explanation:-

50. To protect a bus bar the relay used is

A. ohm relay
B. mho relay
C. reactance relay
D. over current relay

Answer : B. mho relay
Explanation:-

51. With the same secondary burden, in which overcurrent relay, the core saturation occurs at a very early state?

A. definite time overcurrent relay
B. inverse definite time overcurrent relay
C. very inverse overcurrent relay
D. extremely inverse overcurrent relay

Answer : A. definite time overcurrent relay
Explanation:-

52. when a fault occurs on the bu bar itself, there has to be a complete shutdown in case of ________ system

A. double bus bar
B. sectionalised double bus bar
C. single bus bar
D. sectionalised single bus bar

Answer : C. single bus bar
Explanation:-

53. A 3 phase star/delta transformer rated for 11kv/6.6kv and current transformer on the low voltage side has a ratio of 300/5. Determine the ratio of the current transformer on the high voltage side

A. 500:5
B. 180:5
C. 500:5/√3
D. 180:5/√3

Answer : D. 180:5/√3
Explanation:-

54. The neutral of 10MVA,11KV alternator is grounded through a resistance of 5 ohms. The earth fault relay relaying operates at 0.75A. If CT ratio is 1000/5, the percentage of armature winding protected is

A. 88.2
B. 11.8
C. 10
D. 90

Answer :A. 88.2
Explanation:-

55. The equivalent radius of a bundle conductor having its 4 sub conductors of each radius r on the periphery of a circle of diameter d is given by

A. [(r d^2/2)]^(1/4)
B. [(r d^3/2)]^(1/4)
C. [(r d^2/4)]^(1/4)
D. [(r d^3/4)]^(1/4)

Answer : B. [(r d^3/2)]^(1/4)
Explanation:-

56. The transmission efficiency increases with

A. decrease in power factor and increase in voltage level
B. decrease in power factor and decrease in voltage level
C. increase in power factor and increase in voltage level
D. increase in power factor and decrease in voltage level

Answer : C. increase in power factor and increase in voltage level
Explanation:-

57. The range of the medium length transmission line is

A. 50km - 80km
B. 10km - 50km
C. 80km - 160km
D. 170km - 300km

Answer :C. 80km - 160km
Explanation:-

58. Bundled conductors are mainly used in high volatge overhead transmission lines to

A. reduce transmission line losses
B. reduce corona
C. reduce sag
D. increase mechanical strength of the line

Answer :B. reduce corona
Explanation:-

59. Identify the incorrect statement

A. corona increase with increase in spacing between the conductors
B. corona increases the effective capacitance of the line
C. corona increases the electromagnetic and electrostatic interference with the communication system
D. corona increases with increase in system frequency

Answer : A. corona increase with increase in spacing between the conductors
Explanation:-

60. Power control in HVDC link is achieved by

A. varying DC link current
B. varying DC link converter voltage
C. line compensation
D. power factor of load

Answer : B. varying DC link converter voltage
Explanation:-

61. Identify the correct and incorrect statements among the following which refer to sag in the overhead line conductors
1. catenary is the shape attained by the line conductor, if suspended from the towers of the same height
2. with the increase in temperature, sag and tension in the conductor increases
3. sag is directly propertional to the span between the towers
4. stringing charts are useful for adjusting sag and tension in the conductor

A. 1,2 are correct 3,4 are incorrect
B. 1,2,4 are correct 3 is incorrect
C. 1,4 are correct 2,3 are incorrect
D. 1,3,4 are correct 2 is incorrect

Answer :C. 1,4 are correct 2,3 are incorrect
Explanation:-

62. The insulators used for high voltage transmission lines are

A. suspension insulators
B. pin insulators
C. shackle insulators
D. cone insulators

Answer : A. suspension insulators
Explanation:-

63. A string insulator has 4 disc insulator units. the voltage across the bottom most unit nearer to the line conductor is 33.33% of rated voltage. Its percentage string efficiency

A. 25%
B. 33.33%
C. 66.66%
D. 75%

Answer : D. 75%
Explanation:-

64. The sheating of underground cables is commonly done by

A. lead
B. iron
C. copper
D. rubber

Answer :A. lead
Explanation:-

65. Two single core cables made up of same type of core with equal dia, and same dielectric medium have distance from their surface to centre of the core equal to r1,r2 with r1>r2 respectively. If both cables are exposed to same voltage stress, then the cable capacitance C1,C2 and leakage resistance R1,R2 per unit length will be related as

A. C1=C2 and R1=R2
B. C1=C2 and R1>R2
C. C1>C2 and R1=R2
D. C1∠C2 and R1>R2

Answer : D. C1∠C2 and R1>R2
Explanation:-

66. Which of the following distribution systems is more reliable

A. radial system
B. ring main system
C. tree system
D. axial system

Answer : B. ring main system
Explanation:-

67. Identify the false statement among the following, which refer to illumination system

A. solid angle subtented by a sphere at its center is 4π steradians
B. the unit for luminous intensity is candela
C. phot and lux are units of illumination and 1phot = 1000 lux
D. brightness is defined as the intensity of a source in a given direction divided by the orthogonal projected area of the source in that direction

Answer : C. phot and lux are units of illumination and 1phot = 1000 lux
Explanation:-

68. A 60W lamp gives a luminous flux of 1500 lumen. Its efficiency is

A. 1500 lumen/watt
B. 250 lumen/watt
C. 25 lumen/watt
D. 2.5 lumen/watt

Answer : C. 25 lumen/watt
Explanation:-

69. Identify the incorrect statement among the following, which refer to the requirements of a good heating coil for indirect resistance heating

A. it should have high specific resistance
B. it should have a high temperature coefficient of resistance
C. it should have a high melting point
D. it should be free from oxidation

Answer :B. it should have a high temperature coefficient of resistance
Explanation:-

70. The operation of a direct arc furnace requires

A. high voltage
B. high current
C. high power factor
D. low current

Answer :B. high current
Explanation:-

71. In which type of resistance welding, the surface to be welded must be clean and dust and dirt free?

A. spot welding
B. butt welding
C. seam welding
D. projection welding

Answer : C. seam welding
Explanation:-

72. Steel rails are welded by ______ welding

A. argon arc
B. resistance
C. thermit
D. gas

Answer : C. thermit
Explanation:-

73. A suburban train service has the following trapezoidal speed time curve. Determine the distance between the two stations in Km

A. 35/6 km
B. 95/6 km
C. 115/6 km
D. 135/6 km

Answer : B. 95/6 km
Explanation:-

74. Specific energy consumption is minimum in

A. main line service
B. sub urban service
C. urban service
D. for all types

Answer : A. main line service
Explanation:-

75. Two DC series motors having identical rating and speed current characteristics are mounted on the same axial, driving the electric locomotive. If the train is running at constant speed and the wheel driven by motor A is slightly larger in diameter as compared to the wheel driven by motor B, then

A. Motor A draws more current than motor B from the supply main
B. A. Motor A draws less current than motor B from the supply main
C. Motor A and B draw equal current from the supply main
D. The current drawn by the motors A and B are independent of wheel diameters

Answer :A. Motor A draws more current than motor B from the supply main
Explanation:-

76. Which of the following lamps emit monochromatic light?

A. mercury vapour lamp, fluorescent tube
B. mercury vapour lamp, sodium vapour lamp
C. sodium vapour lamp, fluorescent tube
D. neon lamp, fluorescent tube

Answer : B. mercury vapour lamp, sodium vapour lamp
Explanation:-

77. Identify the correct and incorrect statements of the following which refer to a thermal starter in a Fluorescent tube light circuit
1. The bimettalic strip in the thermal starter, make contact with each other when no current is passing through
2. The bimettalic strips in the thermal starter, make contact with each other when current start passing through
3. Heater coil and bimettalic strips of the thermal starter are connected in parallel in the circuit
4. Heater coil and bimettalic strips of the thermal starter are connected in series in the circuit

A. 1,3 are correct: 2,4 are incorrect
B. 2,4 are correct: 1,3 are incorrect
C. 1,4 are correct: 2,3 are incorrect
D. 2,3 are correct: 1,4 are incorrect

Answer : C. 1,4 are correct: 2,3 are incorrect
Explanation:-

78. Which type of starter is suitable for very high rating AC Motors?

A. DOL Starter
B. Auto transformer starter
C. Star-delta starter
D. 4-pointer starter

Answer : B. Auto transformer starter
Explanation:-

79. Pin insulators are designed for a voltage rating of _______, and they are uneconomical in the lines with voltages beyond ______

A. 11kv, 11kv
B. 33kv, 66kv
C. 11kv, 33kv
D. 33kv, 132kv

Answer : C. 11kv, 33kv
Explanation:-

80. An electrical apparatus connected across a single phase 200V AC supply mains. The supply system is neutral grounded through 5ohm resister. Also the apparatues is grounded through a 5ohm resistor. Under insulation failure of the apparatus, what could be the approximate current that may flow through the body of a person touching the apparatus? Take body resistance of the person equal to 1000ohm.

A. 0.1A
B. 1A
C. 5A
D. 10A

Answer : A. 0.1A
Explanation:-

81. Humming in power transformers is due to

A. rupture of the insulation between windings
B. magnetostatic field between the windings and core
C. electrostatic field between the windings and core
D. break of the windings

Answer : B. magnetostatic field between the windings and core
Explanation:-

82. The potential divider method of biasing is used in apmlifiers to

A. reduce the dc base current
B. limit the input ac signal going to the base
C. make the operating point almost independent of 'β'
D. Reduce the cost of the circuit

Answer : C. make the operating point almost independent of 'β'
Explanation:-

83. The main current crossing the collector junction in a normally biased NPN transistor is

A. a diffusion current
B. a hole current
C. equal to the base current
D. a drift current

Answer : D. a drift current
Explanation:-

84. If the output voltage of a bridge rectifier is 200V, the PIV of each diode will be

A. √2(200) volts
B. 2(200)/π volts
C. π(200) volts
D. (π/2)(200) volts

Answer :D. (π/2)(200) volts
Explanation:-

85. A FET has a gate source bias of -2v. The ac inout signal is ±1.2v. The class of operation will be

A. A
B. B
C. C
D. AB

Answer : A. A
Explanation:-

86. The main function of the transformer used in the output of a power amplifier is to

A. safegaurd the transistor against overheating
B. increase the voltage gain
C. step-up the voltage
D. match the load impedance with dynamic output resistance of the transistor

Answer : D. match the load impedance with dynamic output resistance of the transistor
Explanation:-

87. In RC Coupled amplifier the component producing distortion is

A. capacitor
B. resistor
C. transistor
D. source

Answer : C. transistor
Explanation:-

88. Which of the following circuit is most suitable to generate 1Mhz signal

A. phase shift oscillator
B. wein bridge oscillator
C. colpitt's oscillator
D. Astable multivibrator

Answer : C. colpitt's oscillator
Explanation:-

89. The ASCII Code is a _____ bit code

A. 3
B. 4
C. 7
D. 8

Answer : C. 7
Explanation:-

90. which of the following gate will give high output if and only if it's both inputs are same?

A. NAND
B. NOR
C. EX-OR
D. EX-NOR

Answer : D. EX-NOR
Explanation:-

91. Which of the following gate is known as universal gate ?

A. OR
B. NOR
C. AND
D. NOT

Answer : B. NOR
Explanation:-

92. Identify the correct statement among the following, which refer to IGBT power electronic devices

A. It is a controlled turn-on and turn-off device, and has bidirectional current and bipolar voltage withstanding capabilities
B. It is a controlled turn-on and uncontrolled turn-off device, and has unidirectional current and bipolar voltage withstanding capabilities
C. It is a controlled turn-on and turn-off device, and has unidirectional current and unipolar voltage withstanding capabilities
D. It is a controlled turn-on and uncontrolled turn-off device, and has unidirectional current and unipolar voltage withstanding capabilities

Answer : C. It is a controlled turn-on and turn-off device, and has unidirectional current and unipolar voltage withstanding capabilities
Explanation:-

93. A voltage source 200sin(314t) is applied to a thyristor controlled half wave rectifier with resistance load of 50ohms. If the firing angle is 30 degrees with respect to supply voltage waveforme, the average power in the load is

A. 90.6 Watts
B. 86.3 Watts
C. 60.8 Watts
D. 70.6 Watts

Answer : D. 70.6 Watts
Explanation:-

94. Identify the correct statement which refers to a snubber circuit for SCR protection

A. snubber circuit consists of series RL components, and it is connected in series with SCR for protection against di/dt of gate current
B. snubber circuit consists of series RL components, and it is connected in series with SCR for protection against di/dt of anode current
C. snubber circuit consists of series RC components, and it is connected in parallel with SCR for protection against dv/dt rising gate voltage
D. snubber circuit consists of series RC components, and it is connected in parallel with SCR for protection against dv/dt rising anode voltage

Answer : B. snubber circuit consists of series RL components, and it is connected in series with SCR for protection against di/dt of anode current
Explanation:-

95. In a three phase half wave rectifier, each diode conducts for a duration of

A. 180°
B. 120°
C. 90°
D. 60°

Answer : D. 60°
Explanation:-

96. In a single phase full converter. If α and β are firing and extinction angles respectively, then the load current is

A. continuous if (β-α)∠π
B. discontinuous if (β-α)=π
C. discontinuous if (β-α)>π
D. discontinuous if (β-α)∠π

Answer : D. discontinuous if (β-α)∠π
Explanation:-

97. For a DC-DC chopper with chopping frequency of f Hz when the supply voltage Vs is applied for a time of Ton the value of output voltage is calculated as Vo=

A. Vs/fTon
B. Vsf/Ton
C. VsfTon
D. VsTon/f

Answer :C. VsfTon
Explanation:-

98. In case of DC chopper step-down operation, with k as duty cycle, the output rms of fundamental voltage in terms of input voltage Vs is

A. KVs
B. K^2Vs
C. √K Vs
D. Vs/K

Answer : C. √K Vs
Explanation:-

99. RC snubber circuit is used to limit the rate of

A. rise of current in SCR
B. rise of voltsge scross SCR
C. conduction period
D. rise of power across SCR

Answer : B. rise of voltsge scross SCR
Explanation:-

100. The advantage of using PWM switching in voltage source inverters is

A. filter size is increased
B. output voltage cannot be controlled
C. harmonics are not eliminated from the output wave
D. filter size is reduced

Answer : D. filter size is reduced
Explanation:-