FUNCTION -5 (ELECTRICAL)

32. Current applied to lead acid battery would lead to
    1. Higher thermal voltage
    2. Lower terminal voltage high charging
    3. Increase generation of H₂ gas
    4. Decrease in specific gravity of electrolyte

ANS.: C

33. Across the line starters are used with AC motors to provide
    1. Reduced starting current
    2. Regulated starting current
    3. High starting torque
    4. Controlled starting acceleration

ANS.: C

34. In an earth neutral system, an earth fault will occur only
    1. 1 fault in 1 line
    2. 2 fault in two line
    3. Two fault in 1 line
    4. Don’t know

ANS.: A

35. Which statement is true for any storage battery?
    1. Amp hr. efficiency of alkaline battery is high than lead acid battery
    2. Watt hr. efficiency of alkaline is more than lead acid battery
    3. Alkaline battery can left in any state of charge or discharge
    4. All

ANS.: C

36. Which of the following is true about star delta starters
    1. Popular because relatively inexpensive
    2. Gives lower starting current than DOL
    3. Can only be used with induction motor delta connected in supply voltage
    4. Typically used to start the motor with lower voltage

ANS.: B,C,D

37. Which of the following are true for shipboard storage batteries?
    1. Construction should be so as to prevent emission of spray
    2. If voltage is above 200v insulation stands must be used
    3. The deck below the cells should be protected with acid resisting or alkaline resisting materials
    4. Battery banks above 2 kw should be kept in battery room only
    5. Emergency batteries should never be stored in battery room

ANS.: A,C,D

38. In common collector transistor collector amplifier voltage gain
    1. Cannot exceed unity
    2. Depends on output impedance
    3. Depends on output signal
    4. Always constant

ANS.: A

39. Which statement is true for reactor starter for electrical motor
    1. Minimal reduction in starting torque available
    2. Starting current is limited in proportion to voltage
    3. Advantage of this method is its low cost in comparison to other starters
    4. In reactor starter, a Coil with iron core is connected in parallel with motor during starting

ANS.: B,C

40. Which statement is true about any soft starters used in electrical motor
    1. Soft starters are based on semiconductors
    2. Used to control the stopping of motor
    3. Use of soft starters initially result in lower motor torque
    4. Soft starters progressively increase motor voltage with causing torque or current peak

ANS.: A,B,C

41. Voltage generator by most AC generators is fed from the machine to the bus by means of
    1. Brushes on commutator
    2. Brushes on slip rings
    3. Slip rings on commutator
    4. Direct connection from stator

ANS.: D                                                                      

42. Which of the following are true about a temp measuring circuit employed in in a data logger system?
    1. A Wheatstone bridge can be used in conjunction with a Wheatstone bridge induction thermometer
    2. Thermometer is energized using a constant current source and voltage developed is measured in potentiometer type method
    3. Inductance of thermometer will change with change in temp

1. 2 only
2. 1 & 2 only
3. 1 & 3 only
4. 2 & 3 only

ANS.: C

43. Disadvantage of ward Leonard system
    1. Motor generator set requires lot of space
    2. Overall efficiency of the system is low especially when lightly loaded
    3. System operates in very narrow speed range
    4. Requires high maintenance
    5. Speed regulation is difficult to achieve as motor acceleration is uniform
    6. Expensive

1. abde
2. abdf
3. bcef
4. cdef

ANS.: B

44. Which of the following are benefits of modifying ward Leonard control system by replacing motor set with a thyristor speed controller?
    1. Enhanced speed regulation by making the motor acceleration uniform
    2. Increases efficiency of system especially lightly loaded
    3. Reduces the overall cost
    4. Reduces system maintenance
    5. Increases operating speed range of system
    6. Reduces overall space required

1. abdf
2. bcef
3. bcdf
4. acde

ANS.: C

45. Arrange the following in correct sequence foe achieving correct KW sharing when an AC generator is paralleled with live bus bar and generator has some owe factor as others in system
    1. Synchronize the incoming generator in terms of voltage, frequency and phase.
    2. Trim voltage of the machine which has/ have lower load current to increase excitation
    3. Increase speed on incoming machine while lowering than that of others connected to system
    4. Adjust machine voltage to keep overall system efficiency ready.
    5. Adjust the governor control switch on main switch board to increase the fuel to its prime mover

1. adc
2. aebc
3. aecb
4. aec     

ANS.: D

47. Which of the following are TRUE with regards to a Synchroscope?
    1. One of the coils in the armature is fed through an Inductor while the other is fed through a Resistor.
    2. The rotating armature has two coil windings parallel to each other.
    3. One of the coils in the armature is fed through a Capacitor while the other is fed through an Inductor.
    4. The field produced by the coils rotates the magnetic armature pointer at a speed relative to the voltage of the bus-bar supply.

ANS.: A

48. Which of the following are TRUE with regards to incorrect synchronization of Alternators?
    1. If incoming supply voltage is higher than that of bus bar, the alternator will start drawing power from bus bar and start motoring.
    2. If incoming supply voltage is lesser than that of bus bar, the alternator will start drawing power from bus bar and start motoring.
    3. If voltages are not in phase and circuit breaker is closed, the phase difference will cause overloading and potential black out.
    4. If voltages are not in phase and circuit breaker is closed, the phase difference will cause low current to flow from alternator and alternator will run on low load.

ANS.: 2,3

49. Max half wave rectifier efficiency possible by two diodes from a sinusoidal wave is
    1. 6
    2. 1
    3. 2
    4. None of the above

ANS.: A

51. An amplifier is said to suffer distortion when its output is
    1. Low
    2. Different from input
    3. Noisy
    4. Larger than is input

ANS.: B

52. What happens when battery is excess charged?
    1. Electrolyte decreases
    2. Gassing increases
    3. Don’t remember
    4. Don’t remember

ANS.: B

53. Which statements are true about starts used for electric motor.
    1. Rheostat starting can be used with slip ring motors
    2. Frequency convertor cannot be used as starter
    3. Soft starter is made of semiconductor
    4. Advantage of Reactor start is their relatively low cost

ANS.: A,C,D

54. Max full wave rectifier efficiency possible by two diodes from a sinusoidal wave is
    1. 80.2
    2. 1
    3. 2  
    4. None of the above

55. An amplifier is said to suffer from distortion when its output is
    1. Low
    2. Different from input
    3. Noisy
    4. Larger than is input

ANS.: B

56. Common emitter amplifier is characterized by
    1. Low voltage gain
    2. Moderate power gain
    3. Signal phase reversal
    4. Very high output impedance

ANS.: C

57. The depletion region in semiconductor diode is due to
    1. Reverse biasing
    2. Forward biasing
    3. Crystal doping
    4. Migration of mobile charge carriers

ANS.: D

59. Which of the following does not change in a transformer
    1. Current
    2. Voltage
    3. Frequency
    4. of turns

ANS.: C

60. Reversing any two of the three rotor leads on induction motor will _____________.
    1. increase motor performance
    2. decrease motor performance
    3. reverse the motor
    4. have no effect on the direction of rotation or motor performance

ANS.: C