AP ECET EEE 2021

1. The demagnetising component of armature reaction in a DC generator

A. reduces generated emf
B. increases armature speed
C. reduces interpoles flux density
D. results in sparking trouble

Answer : A. Reduces generated emf
Explanation:-

2. A 4 pole, lap wound dc genearator has 40 coils with 8 turns per coil. It is driven at 1200rpm. If the flux per pole is 0.022wb, then the generated emf is

A. 265.8 V
B. 276.3 V
C. 281.6 V
D. 287.9 V

Answer : C. 281.6 V
Explanation:-

3. In flemmings right hand rule, the direction of the induced emf in the conductor is given by

A. Index finger
B. Middle finger
C. Thumb
D. Ring finger

Answer : B. Middle finger
Explanation:-

4. The armature reaction effect in DC machines can be neutralised by using

A. only compensating winding
B. only interpoles
C. both compensating winding and interpoles
D. Main field winding

Answer : C. both compensating winding and interpoles
Explanation:-

5. Which of the following motor is having very high no load speed?

A. DC Shunt motor
B. DC series motor
C. DC compound motor
D. Induction motor

Answer : B. DC series motor
Explanation:-

6. If a shunt motor is started with its field winding open then

A. It will rotate at the same speed as that with its field winding closed
B. It will rotate at less speed as that with its field winding closed
C. It will rotate at dangerously high speed
D. It will not rotate

Answer : C. It will rotate at dangerously high speed
Explanation:-

7. If a resistance is added in series with the fiels winding of dc shunt motor

A. both speed and torque decreases
B. both speed and torque increases
C. speed decreases, torque increases
D. speed increases, torque decreases

Answer : D. speed increases, torque decreases
Explanation:-

8. A 220v DC motor draws an armature current of 20A. Its armature resistance is 0.6 ohm. Then the back emf in the motor will be

A. 195V
B. 202V
C. 208V
D. 215V

Answer : C. 208V
Explanation:-

9. The main purpose of performing short circuit test on a transformer is to measure its

A. Copper loss
B. core loss
C. Insulation resistance
D. Total loss

Answer : A. Copper loss
Explanation:-

10. The essential condition for parallel operation of two single phase transformers is that they should have the same

A. KVA Rating
B. Turn Ratio
C. Size
D. Polarity and turn ratio

Answer : D. Polarity and turn ratio
Explanation:-

11. Which of the following loss in a transformer is zero even at full load?

A. Eddy current loss
B. Core loss
C. Copper loss
D. Friction loss

Answer : D. Friction loss
Explanation:-

12. The size of the transoformer core mainly depends on

A. Air gap
B. Area of core
C. Flux density of core
D. Frequency and area of core

Answer : D. Frequency and area of core
Explanation:-

13. Open delta transformers can be obtained from

A. Delta Delta
B. Star Delta
C. Delta Star
D. Only star

Answer : A. Delta Delta
Explanation:-

14. What are the modes in which power can be transferred in an autotransformer?

A. Conduction and intension
B. Induction and intension
C. Conduction and Induction
D. Cannot be said

Answer : C. Conduction and Induction
Explanation:-

15. In a transformer the resistance between its primary and secondary is

A. Zero
B. Infinite
C. 1000 ohm
D. 100 ohm

Answer : B. Infinite
Explanation:-

16. Alternator on infinite bus bar has constant

A. Terminal voltage and frequency
B. Frequency
C. Power factor
D. Power factor and terminal voltage

Answer : A. Terminal voltage and frequency
Explanation:-

17. The rating of the alternator is decided by

A. Losses
B. Voltage
C. Armature current
D. Temperature

Answer : A. Losses
Explanation:-

18. The short circuit characteristics of alternator is a straight line due to

A. No saturation
B. No armature reaction
C. No eddy current
D. No hysteresis loss

Answer : A. No saturation
Explanation:-

19. What happens if field winding of thr synchronous motor is short circuited?

A. First, it starts as induction motor then run as synchronous motor
B. it will not start
C. Motor will burn out
D. It runs as induction motor

Answer : D. It runs as induction motor
Explanation:-

20. The armature current of the synchronous motor has large values for

A. High Excitation
B. Unity power factor
C. Both high and low excitation
D. only at low excitation

Answer : C. Both high and low excitation
Explanation:-

21. The damper winding in a synchronous motor is provided for

A. starting torque only
B. reducing eddy currents
C. preventing hunting and providing the starting torque
D. reducing the noise level

Answer : C. preventing hunting and providing the starting torque
Explanation:-

22. If autotransformer method of starting is used to start an induction motor to replace star-delta method, then the required tapping on the transformer will be

A. 57.73%
B. 86.7%
C. 57%
D. 66.66%

Answer : A. 57.73%
Explanation:-

23. Three phase supply is fed to the induction motor and is running at its normal operating conditions. Then the synchronous speed can be defined as speed at which?

A. stator magnetic field rotates
B. rotor magnetic field rotates
C. rotor rotates
D. slip speed

Answer : A. stator magnetic field rotates
Explanation:-

24. A 4pole three phase induction motor having synchronous speed of 1500rpm is operating at 1450rpm. The frequency of the induced emf in rotor is ?

A. 1.667Hz
B. 16.667Hz
C. 0.1667Hz
D. 166.667Hz

Answer : A. 1.667Hz
Explanation:-

25. In a 3phase slip ring induction motor high starting torque is acheived by

A. Increasing supply voltage
B. Increasing supply frequency
C. Connecting a capacitor across the motor terminals
D. Connecting a star connected resistance across slip ring terminals of motor

Answer : D. Connecting a star connected resistance across slip ring terminals of motor
Explanation:-

26. In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to

A. improves power factor
B. reduce fluctuations in torque
C. increase overload capacity
D. to improve torque

Answer : A. improves power factor
Explanation:-

27. In split phase motor, the main winding is made up of

A. Thick wire placed at the top of the slots
B. Thick wire placed at the bottom of slots
C. Thin wire placed at the top of the slots
D. Thin wire placed at the bottom of thr slots

Answer : B. Thick wire placed at the bottom of slots
Explanation:-

28. The power factor of a single phase load can be calculated if the instruments available are

A. One voltmeter and one ammeter
B. One voltmeter, one ammeter and one wattmeter
C. one voltmeter, one ammeter and one energy meter
D. only wattmeter

Answer : B. One voltmeter, one ammeter and one wattmeter
Explanation:-

29. In a single phase power factor meter the phase difference between the currents in the two pressure coils is

A. Exactly 0 degrees
B. Approximately 0 degrees
C. Exactly 90 degrees
D. Approximately 90 degrees

Answer : C. Exactly 90 degrees
Explanation:-

30. The disc of an instrument using eddy current damping should be made of

A. Conducting and magnetic material
B. Non-conducting and magnetic material
C. Conducting and non magnetic material
D. Only conducting material

Answer : C. Conducting and non magnetic material
Explanation:-

31. If damping torque is not provided in an instrument

A. An instrument will show full wave of quantity even under small values
B. The pointer will move only when full rated load is provided
C. The pointer will oscillate about its final deflected position and will never come to rest even under steady conditions
D. The pointer will oscillate about its final deflected position for quite some time before coming to rest

Answer : D. The pointer will oscillate about its final deflected position for quite some time before coming to rest
Explanation:-

32. What should be the height of the 'Roof Pole'

A. 3m
B. less than 3m
C. more than 3m
D. cannot be decided

Answer : B. less than 3m
Explanation:-

33. Earthing is necessary to give protection against

A. danger of electric shock
B. voltage fluctuation
C. overloading
D. high temperature of the conductors

Answer : A. danger of electric shock
Explanation:-

34. The earthing rod orientation in the pit should be

A. 45 degrees
B. horizontal
C. vertical
D. 75 degrees

Answer : C. vertical
Explanation:-

35. What is the cause for mechanical overloads in the induction motors?

A. stalling
B. blowing of fuse
C. under voltage
D. open circuit

Answer : A. stalling
Explanation:-

36. Locomotives with monometer bogies have

A. uneven distribution of the tractive effect
B. suitability for passenger as well frieght service
C. lot of skidding
D. low coefficient of adhesion

Answer : B. suitability for passenger as well frieght service
Explanation:-

37. Specific energy consumption is least in ________ service

A. Main line
B. urban
C. suburban
D. Rural service only

Answer : A. Main line
Explanation:-

38. The coasting retardation is around

A. 16km phps
B. 1.6km phps
C. 0.16km phps
D. 40 km phps

Answer : C. 0.16km phps
Explanation:-

39. Overhead lines for power supply to tram cars at a minimum height of

A. 3m
B. 6m
C. 10m
D. 15m

Answer : C. 10m
Explanation:-

40. The rate of acceleration on suburban or urban services is restricted by the consideration of

A. Engine power
B. Track curves
C. Passenger discomfort
D. Track size

Answer : C. Passenger discomfort
Explanation:-

41. Which of the following is the advantage of electric braking?

A. It is instantaneous
B. more continous to ramain loaded during braking
C. it avoids wear of track
D. more heat is generated during braking

Answer : C. it avoids wear of track
Explanation:-

42. The value of coefficient of adhesion will be high when rails are

A. greased
B. cleaned with sand
C. sprayed with oil
D. wet

Answer : B. cleaned with sand
Explanation:-

43. Which of the following is the disadvantage of electric traction over other systems of traction?

A. corrosion problems in the underground pipe work
B. short time power failure interrupts traffic for hours
C. high capital outlay in fixed installaions beside route limitation
D. Interference with communication lines

Answer : C. high capital outlay in fixed installaions beside route limitation
Explanation:-

44. With regards to measuring current and voltage in an AC Circuit modern AC instruments are calibrated to read

A. RMS value
B. Peak values
C. Average values
D. Form factor values

Answer : A. RMS value
Explanation:-

45. The current waveform for a purely resistive circuit

A. leads the voltage by 90
B. is in phase with the voltage
C. lags the voltage by 90
D. alternately leads and lags the voltage

Answer : B. is in phase with the voltage
Explanation:-

46. When two capacitors are connected in series, the total capacitance

A. is doube the capacitance of any one
B. is decreased
C. is increased
D. remains the same as the largest one

Answer : B. is decreased
Explanation:-

47. The power factor of an AC circuit can be found using formula, power factor =

A. volt-amperes/watts
B. volt-amperes x current
C. watts/volt-amperes
D. volt x volt-amperes

Answer : C. watts/volt-amperes
Explanation:-

48. The reactive power can be measured with wattmeter when voltage across voltage coil is adjusted to be out of phase with the current by

A. 90 degrees
B. 180 degrees
C. 45 degrees
D. 0 degrees

Answer : A. 90 degrees
Explanation:-

49. The 8051 microcontroller is of _____ pin package as a _______ processor

A. 30, 1byte
B. 20, 1 byte
C. 40, 8 bit
D. 40, 8 byte

Answer : C. 40, 8 bit
Explanation:-

50. what is the address range of SFR register bank?

A. 00H-77H
B. 40H-80H
C. 80H-7FH
D. 80H-FFH

Answer : D. 80H-FFH
Explanation:-

51. Serial port interrupt is generated, if ____ bits are set

A. IE
B. RI,IE
C. IP, TI
D. RI, TI

Answer : D. RI, TI
Explanation:-

52. In 8051 which interrupt has high priority?

A. IE1
B. TF0
C. IE0
D. TF1

Answer : C. IE0
Explanation:-

53. The condition for the validity of ohms law is that the

A. temperature should remain constant
B. current should be proportional to voltage
C. resistance must be wire wound type
D. resistance must be varying type

Answer : A. temperature should remain constant
Explanation:-

54. Property of a material which opposes the production of magnetic flux in it is called

A. MMF
B. Reluctance
C. Permeance
D. Permitivity

Answer : B. Reluctance
Explanation:-

55. Resistance of the conductor is doubled keeping the potential difference across it constant. The rate of generation of heat will be

A. be halved
B. becomes four times
C. become one fourth
D. be doubled

Answer : A. be halved
Explanation:-

56. Which of the following statement is not correct about magnetic field?

A. Magnetic field lines form a continous closed curve
B. magnetic field line do not intersect each other
C. direction of tangent at any oint on the magnetic field line curve gives the direction of magnetic field at that point
D. outside the magnet, magnetic field lines go from south to north pole of the magnet

Answer : D. outside the magnet, magnetic field lines go from south to north pole of the magnet
Explanation:-

57. what happens to the force acting between the charged particles, if the distance between them is halved?

A. it increases by four times
B. it gets doubled
C. it becomes half
D. it reduces by one fourth

Answer : A. it increases by four times
Explanation:-

58. Which of the following is a semiconductor material?

A. phosphorous
B. rubber
C. silicon
D. aluminium

Answer : C. silicon
Explanation:-

59. Which of the following circuit element is an active component?

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

Answer : B. transistor
Explanation:-

60. Which of thr following generation station has minimum running cost?

A. Thermal power station
B. Hydro-electric power station
C. Nuclear power station
D. gas based power station

Answer : B. Hydro-electric power station
Explanation:-

61. Economiser is used to heat

A. air
B. feed water
C. flue gases
D. smoke

Answer : B. feed water
Explanation:-

62. Kaplan turbine is used for ______ hydro electric plant

A. medium and low head
B. high head
C. low head
D. low and high head

Answer : C. low head
Explanation:-

63. The function of a surge tank is _______

A. to supply water at constant pressure
B. to produce surges in the pipe line
C. to relieve water hammer pressures in the penstock pipe
D. to produce varying pressure

Answer : C. to relieve water hammer pressures in the penstock pipe
Explanation:-

64. when nuclear reactor is operating at constant power, the multiplication factor is _______

A. equal to unity
B. more than unity
C. less than unity
D. zero

Answer : A. equal to unity
Explanation:-

65. The most appropriate operating speeds in rpm of generators used in thermal, nuclear and hydro-power plants would respectively be

A. 3000, 300 and 1500
B. 3000, 3000 and 300
C. 1500, 1500 and 3000
D. 1000, 900 and 750

Answer : B. 3000, 3000 and 300
Explanation:-

66. To limit current chopping in vacuum circuit breakers, the contact material used has

A. high vapour pressure and low conductivity properties
B. high vapour pressure and high conductivity properties
C. low vapour pressure and high conductivity properties
D. low vapour pressure and low conductivity properties

Answer : A. high vapour pressure and low conductivity properties
Explanation:-

67. A mho is a

A. voltage restrained directional relay
B. volatge controlled over current relay
C. directional restarined over current relay
D. directional restrained over volatge relay

Answer : A. voltage restrained directional relay
Explanation:-

68. The normal practice to specify the making current of a circuit breaker is in

A. RMS value
B. peak value
C. Average value
D. Form factor

Answer : B. peak value
Explanation:-

69. Auto reclosing is used in case of

A. Lightning arrestor
B. Air blast circuit breaker
C. Bulk oil circuit breaker
D. Minimum oil circuit breaker

Answer : B. Air blast circuit breaker
Explanation:-

70. Ring main distribution is preferred to a radial system because

A. voltage drop in the feeder is less and supply is more reliable
B. voltage drop in the feeder is less and power factor is high
C. power factor is high and supply is more reliable
D. power factor is high and system is less expensive

Answer : A. voltage drop in the feeder is less and supply is more reliable
Explanation:-

71. The good effect of corona on overhead lines is to

A. increase the line carrying capacity due to conducting ionised air envelop around the conductor
B. increase the power factor due to corona loss
C. reduce the radio interference from the conductor
D. reduce the steepness of surge fronts

Answer : D. reduce the steepness of surge fronts
Explanation:-

72. The values of A,B,C and D constants for a short transmission lin are respectively

A. Z,0,1 and 1
B. 0,1,1 and 1
C. 1,Z,0 and 1
D. 1,1,Z and 0

Answer : C. 1,Z,0 and 1
Explanation:-

73. Between two supports, due to sag the conductor takes the form of

A. catenary
B. triangle
C. ellipse
D. semi-circle

Answer : A. catenary
Explanation:-

74. Whenever the conductors are dead ended or there is a change in the direction of transmission line, the insulators used are of the

A. Pin type
B. Suspension type
C. Strain type
D. Shackle type

Answer : C. Strain type
Explanation:-

75. Transmission lines are transposed to

A. reduce copper loss
B. reduce skin effect
C. prevent interference with neighbouring telephone lines
D. prevent shirt circuit between any two lines

Answer : C. prevent interference with neighbouring telephone lines
Explanation:-

76. The voltages across various discs of suspension insulators having identical discs is different due to

A. surface leakage currents
B. series capacitance
C. shunt capacitances to ground
D. series and shunt capacitances

Answer : C. shunt capacitances to ground
Explanation:-

77. sheaths are used in cables to

A. provide proper insulation
B. provide mechanical strength
C. prevent ingress of moisture
D. prevent current

Answer : C. prevent ingress of moisture
Explanation:-

78. Stringing chart is useful for

A. finding the sag in the conductor
B. in the design of tower
C. in the design of insulator string
D. finding the distance between the tower

Answer : A. finding the sag in the conductor
Explanation:-

79. Charging current in medium transmission line is

A. maximum at receiving end
B. maximum at sending end
C. more in between sending end and receiving end
D. equal throughtout the line

Answer : A. maximum at receiving end
Explanation:-

80. A PN junction acts as a

A. controlled switch
B. birectional switch
C. unidirectional switch
D. open circuit

Answer : C. unidirectional switch
Explanation:-

81. Zener diode can be described as

A. a rectifier diode
B. a device with constant voltage
C. a device with constant current
D. a device that works in the forward region

Answer : B. a device with constant voltage
Explanation:-

82. A 4-variable AND-OR Circuit produces a 1 at its Y output. Which combination of inputs is correct?

A. A=0, B=0, C=0, D=0
B. A=0, B=1, C=1, D=0
C. A=1, B=1, C=0, D=0
D. A=1, B=0, C=0, D=0

Answer : C. A=1, B=1, C=0, D=0
Explanation:-

83. What type of logic circuit is represented by the figure shown below?

A. XOP
B. XNOR
C. XAND
D. XNAND

Answer : B. XNOR
Explanation:-

84. Which of the following expression is in the sum of products form?

A. (A+B)(C+D)
B. (AB)(CD)
C. AB(CD)
D. AB+CD

Answer :D. AB+CD
Explanation:-

85. What is the binary subtractionof 101001-010110=?

A. 010011
B. 100110
C. 011001
D. 010010

Answer : A. 010011
Explanation:-

86. Oscillators are used to _____ AC Voltage

A. prevent
B. generate
C. Amplify
D. Rectify

Answer : B. generate
Explanation:-

87. The output of oscillator will not depend upon _______

A. feedback
B. amplifier
C. both feedback and amplifier
D. input voltage

Answer : D. input voltage
Explanation:-

88. The use of amplifier in a circuit is to ________ for input signal

A. provide a phase shift
B. provide strength
C. provide frequency enhancement
D. make circuit compatible

Answer : B. provide strength
Explanation:-

89. DC average current of a centre tapped full wave rectifier is _______

A. 2Im/∏
B. Im/∏
C. Im/2∏
D. 1.414Im/∏

Answer : A. 2Im/∏
Explanation:-

90. For a NPN bipolar transistor, what is the main stream of current in the base region?

A. Drift of holes
B. Diffusion of holes
C. Drift of electrons
D. Diffusion of electrons

Answer : B. Diffusion of holes
Explanation:-

91. A thyristor can be brought from the forward conduction mode to forward

A. The dv/dt triggering method
B. Applying a negative gate signal
C. applying a positive gate signal
D. applying a reverse voltage across anode-cathode terminals

Answer : D. applying a reverse voltage across anode-cathode terminals
Explanation:-

92. di/dt protection is provided to the thyristor by

A. Connecting an inductor in parallel across the load
D. applying a reverse voltage across anode-cathode terminals
C. Connecting an inductor in parallel across the gate terminal
D. Connecting an inductor in series with the gate

Answer : D. applying a reverse voltage across anode-cathode terminals
Explanation:-

93. SCR are connected in parallel to fulfill the _______ demand

A. High current
B. High current
C. size
D. Efficiency

Answer : B. High current
Explanation:-

94. The GTO can be turned off

A. by a positive gate pulse
B. by a negative gate pulse
C. by a negative anode-cathode voltages
D. by removing the gate pulse

Answer : B. by a negative gate pulse
Explanation:-

95. A single phase full converter using R load is a ______ quadrant converter and that using an RL load without FD is a ________ quadrant converter

A. One, one
B. Two, one
C. One, two
D. Two, two

Answer : C. One, two
Explanation:-

96. A chopper may be thought as a

A. An inverter with DC input
B. A DC equivalent of an AC transformer
C. A diode rectifier
D. A DC equipment of an induction motor

Answer : B. A DC equivalent of an AC transformer
Explanation:-

97. In case of the 120degrees mode of opertion. _________ devices conduct at a time

A. 2
B. 3
C. 4
D. 6

Answer :A. 2
Explanation:-

98. Which one of the following is the main advantage of the SMPS over linear power supply?

A. No transformer is required
B. Only one stage of conversion
C. No filter is required
D. Low power dissipation

Answer : D. Low power dissipation
Explanation:-

99. _______ is used for critical loads where temporary power failure can cause a great deal of inconvenience

A. SMPS
B. UPS
C. MPS
D. RCCB

Answer : B. UPS
Explanation:-

100. In order to prevent distortion in the output signal after amplification, the input signal must be

A. be higher than the positive saturation level of the amplifier
B. be lower than the negative saturation level of the amplifier
C. lie with the negative and the positive saturation level of the amplifier
D. be both higher than the positive saturation level of the amplifier and lower than the negative saturation level of the amplifier

Answer : C. lie with the negative and the positive saturation level of the amplifier
Explanation:-