EEE MCQ (Electrical Machine Design)

Electrical Machine Design Multiple Choice Questions and Answers Preparation for Competition exams

1. Which of the following is the major consideration to evolve a good design ?
(a)     Cost   
(b)     Durability
(c)    Compliance with performance criteria as laid down in specifications
(d)    All of the above
Ans: d
2    impose limitation on design.
(a)    Saturation
(b)    Temperature rise
(c)    Efficiency   
(d)     Power factor
(e)    All above
Ans: e

3.    The efficiency of a machine should be as ______    as possible to reduce the operating cost.
(a)     high   
(b)     low
(c)    either of the above
(d)    none of the above
Ans: a

4.    If an insulating material is operated beyond the maximum allowable temperature, its life is
(a)     drastically increased
(b)     drastically reduced
(c)      unaffected
(d)      none of the above
Ans: b

5.    The design of mechanical parts is particularly important in case of _____ speed machines.
(a)    low   
(b)    medium
(c)    high   
(d)    any of the above
Ans: c

6.    In induction motors, the length of air gap in kept as small as mechanically possible is order to have
(a)     low power factor
(b)     high power factor
(c)    high over load capacity
(d)    any of the above
Ans: b

7.    In ______ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft.
(a)     small   
(b)     medium
(c)     large   
(d)     any of the above.
Ans: c

8.    The length cf air gap to be provided in ______ is primarily determined by power factor consideration.
(a)     d.c. series motor .
(b)     d.c. shunt motor
(c)     induction motor
(d)    synchronous motor
Ans: c

9.   Electrical machines having a power output upto about 750 W may be called_______machines.
(a)    small size   
(b)    medium size
(c)    large size   
(d)    any of the above
Ans: a

10.    Electrical machines having power outputs ranging from a few kW upto approximately 250 kW may be classified as   
(a)     small size machines
(b)     medium size machines
(c)    large size machines
(d)    any ofthe above
Ans: b

11.    Commercial available medium size machines have a speed range of    ______ .
(a)     200 to 400 r.p.m.
(b)     600 to 1000 r.p.m.
(c)    1000 to 1500 r.p.m.
(d)    2000 to 2500 r.p.m.
Ans: d

12.    The action of electromagnetic machines can be related to which ofthe following basic principles ?
(a)     Induction   
(b)     Interaction
(c)     Alignment   
(d)     All of the above
Ans: d

13.    The change in flux linkages can be caused in which ofthe following ways ?
(a)    The flux is constant with respect to time and is stationary and the coil moves through it
(b)    The coil is stationary with respect to flux and the flux varies in magnitude with respect to time
(c)    Both the changes mentioned above occure together, i.e., the coil moves through a time varying field
(d)    All ofthe above
Ans: d

14    is universally used for windings of electrical machines because it is easily workable without any possibility of fracture.
(a) Silver   
(b) Steel
(c) Aluminium       
(d) Copper
Ans: d

15. Aluminium when adopted as a conductor material in ______ transformers, decreases the overall cost of the transformer
(a)     small size   
(b)     medium size
(c)    large size
(d)    any of the above size
Ans: a

16.    Which ofthe following materials is used in the manufacture of resistance grids to be used in the starters of large motors ?
(a)     Copper   
(b)     Aluminium
(c)     Steel   
(d)     Cast-iron
Ans: d

17.    Materials exhibiting zero value of resistivity are known as ______ .   
(a)     conductors   
(b)     semiconductors
(c)     insulators   
(d)     superconductors
Ans: d

18.  ________ has a lowrelative permeability and is used principally in field frames when cost is of primary importance and extra weight is not objectionable.
(a)     Cast steel   
(b)     Aluminium
(c)     Soft steel   
(d)     Cast iron
Ans: d

19    ______is extensively used for those portions of magnetic circuit which carry steady flux and need superior mechanical properties ?
(a)     Grey cast-iron  
(b)     Cast steel
(c)    High carbon steel
(d)    Stainless steel
Ans: b

20.    Hot rolled sheets have ______ value of permeability
(a)     zero   
(b)     low
(c)     high   
(d)     none ofthe above
Ans: b

21.    The heated parts of an electrical machine dissipate heat into their surroundings by which of the following modes of heat dissipation ?
(a)    Conduction      
(b)    Convection
(c)    Radiation   
(d)    All ofthe above
Ans: d

22.    The heat dissipated by    from a surface depends upon its temperature and its characteristics like colour, roughness etc.
(a)     conduction       
(b)     convection
(c)     radiation   
(d)     any ofthe above
Ans: c

23.    The mcrease in heat dissipation by air blasts is due to increase in   
(a)     conduction   
(b)     convection
(e)    radiation   
(d)     any ofthe above
Ans: b

24.    On which of the following variables heat convected depends ?
(a)     Power density
(b)     Temperature difference between heated surface and coolant
(c)    Thermal resistivity, density, specific heat
(d)    Gravitational constant
(e)    All ofthe above
Ans: e

25.    Which ofthe following methods is used for air cooling of turbo-alternators ?
(a)    One sided axial ventilation
(b)    Two sided axial ventilation
(c)    Multiple inlet system
(d)    All ofthe above
Ans: d

26.    Multiple inlet system of air cooling of turbo-alternators can be used for machines of rating upto
(a)    10 MW   
(b)    30 MW
(c)    60 MW   
(d)    150 MW
Ans: c

27.    Which ofthe following is an advantage of hydrogen cooling ?
(a)     Increase in efficiency
(b)     Increase in ratings
(c)    Increase in life
(d)    Smaller size of coolers
(e)    All ofthe above
Ans: e

28.    The density of hydrogen is _____ times the density of air.
(a)    0.07   
(b)    1.5
(c)    2.5   
(d)    3.5
Ans: a

29.    Hydrogen has a heat transfer co-efficient _____    times that of air
(a)    1.5   
(b)    2.5
(c)    3.5   
(d)    4.5
Ans: a

30.    The thermal conductivity of hydrogen is    ______ times that of air
(a)    2   
(b)    3
(c)    5   
(d)    7
Ans: d

31.    With conventional hydrogen cooling it is possible to increase the rating of a single unit to
(a)     50 MW   
(b)     100 MW
(c)    200 MW
(d)    none ofthe above
Ans: c

32.    The noise produced by a ______ cooled machine is less as the rotor moves in a medium of smaller density.
(a)     air   
(b)     hydrogen
(c)    either (a) or (b)
(d)    none of the above
Ans: b

33    cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall
(a)    Direct   
(b)    Indirect
(c)    Conventional    
(d)    Any ofthe above
Ans: a

34.    Machines cooled by direct cooling method may be called
(a)     "supercharged"
(b)     "inner cooled"
(c)    "conductor cooled"
(d)    any of the above
Ans: d

35.    In direct cooled system using hydrogen both stator and rotor conductors are made
(a)    solid   
(b)    hollow
(c)    perforated   
(d)    any ofthe above
Ans: b

36.    With direct water cooling it is possible to have ratings of about
(a)    200 MW   
(b)    300 MW
(c)    400 MW   
(d)    600 MW
Ans: d

37.    The resistivity of water should not be less than
(a)    10 Q m   
(b)    100 Q m
(c)    1000 Q m   
(d)    2000 Q m
Ans: d

38.    Direct water cooling of rotor winding presents
(a)     no mechanical difficulties
(b)     lesser mechanical difficulties
(c)    greater mechanical difficulties
(d)    none of the above
Ans: c

39.    The time taken by the machine to attain 0.632 of its final steady temperature rise is called
(a)     heating time constant
(b)     cooling time constant
(c)    either (a) or (b)
(d)    none of the above
Ans: a

40.    In self cooled motors the cooling time constant is about ______    than the heating time constant because cooling conditions are worse at standstill.
(a)    2 to 3 times greater
(b)    3 to 4 times greater
(c)    4 to 5 times greater
(d)    none of the above
Ans: a

41.    By which of the following methods motor rating for variable load drives can be determined ?
(a)     Method of average losses
(b)     Equivalent current method
(c)    Equivalent torque method
(d)    Equivalent power method
(e)    All of the above.
Ans: e

42.    Which of the following methods does not take into account the maximum temperature rise under variable load conditions ?
(a)     Equivalent power method
(b)     Equivalent current method
(c)    Method of average losses
(d)    Equivalent torque method
Ans: c

43.    Which of the following methods is most accurate ?
(a)     Equivalent current method
(b)     Equivalent power method
(c)    Equivalent torque method
(d)    Method of average losses
Ans: a

44.    By which of the following methods the temperature rise of windings and other parts may be determined ?
(a)     Thermometer method
(6)     Resistance method
(c)     Embedded temperature detector method
(d)     Any of the above
Ans: d

45.    The slot leakage can be calculated by making which of the following assumptions ?
(a)     The current in the slot conductors is uniformly distributed over their cross-section
(b)     The leakage path is straight across the slot and around the iron at the bottom
(c)     The permanence of air paths is only considered. The reluctance of iron paths is assumed as zero
(d)     All of the above
Ans: d

46.    The value of exciting or magnetizing current depends upon which of the following factors ?
(a)     Total m.m.f. required
(b)     The number of turns in the exciting winding
(c)    The way in which the winding is distributed
(d)    All of the above
Ans: d

47.   Tractive magnets are operated from
(a)     a.c. supply   
(b)     d.c. supply
(c)    either a.c. or d.c. supply
(d)    none of the above
Ans: c

48    electromagnets generally function as holding magnets.
(a)     Tractive   
(b)     Portative
(c)    Either of the above
(d)    None of the above
Ans: b

49.   Which of the following is the commonly used type of electromagnets ?
(a)     Flat-faced armature type
(b)     Horse shoe type
(c)    Flat-faced plunger type
(d)    All of the above
Ans: d

50    are used for construction of core of electromagnets.
(a)    Soft magnetic materials
(b)    Hard magnetic materials
(c)    Either (a) or (b)
(d)    None of the above
Ans: a

51.    The design of electromagnets is based upon which of the following fundamental equations ?
(a)     Force equation
(b)     Magnetic circuit equation
(c)    Heating equation
(d)    Voltage equation
(e)    All of the above
Ans: e

52.    When the two coil sides forming a coil are spaced exactly one pole pitch apart they are said to be of
(a)     short pitch   
(b)     full pitch
(c)    either of the above
(d)    none of the above
Ans: b

53    are always double layer type.
(a)    Closed windings
(b)    Open windings
(c)    Either of the above
(d)    None of the above
Ans: a

54.   The distance between the starts of two consecutive coils measured in terms of coil sides is called
(a)     front pitch   
(b)     winding pitch
(c)    commutator pitch
(d)    back pitch
 Ans: b

55.    The winding where dummy coils are used is sometimes called
(a)    duplex winding
(b)    triplex winding
(c)    forced winding
(d)    none of the above
Ans: c

56.    Dummy coil should not be used in
(a)     small machines
(b)     large machines
(c)    either (a) or (b)
(d)    none of the above
Ans: b

57.    Power transformers have rating
(a)     equal to 50 kVA
(6)     equal to 100 kVA
(c)    above 200 kVA
(d)    none of the above
Ans: c

58.    Power transformers should be designed to have maximum efficiency
(a)    at one-fourth load
(b)    at one-half load
(c)    at or near full load
(d)     any of the above
Ans: c

59.    In transformers using hot rolled steel, the cross-section of the yoke is made about _____ greater than that of the core
(a)     5 percent   
(b)     10 percent
(c)     15 percent   
(d)     30 percent
(e)     none of the above
Ans: c

60.    Yokes with rectangular cross-section are used for
(a)    small capacity transformers
(b)    medium capacity transformers
(c)    large capacity transformers
(d)     any of the above
Ans: a

61.    The cold rolled grain oriented steel has ______    permeability in the direction of the grain orientation.
(a)    minimum   
(b)    maximum
(c)    nil   
(d)    none of the above
Ans: b

62.    Cylindrical windings using circular conductors, employed in transformers, are
(a)     single layered  
(b)     double layered
(c)    multi-layered
(d)    none of the above
Ans: c

63.    Helical windings are used in
(a)    distribution transformers
(b)    power transformers
(c)    shell type transformers
(d)    none of the above
Ans: b

64.    Multi-layer helical windings are commonly used in the transformers as high voltage windings
(a)     upto 20 kV       
(b)     upto 50 kV
(c)    upto 80 kV
(d)    for 110 kV and above
Ans: d

65.    Disc windings are primarily used in
(a)    short capacity transformers
(b)    medium capacity transformers
(c)    high capacity transformers
(d)    any of the above
Ans: c

66.    The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following ?
(a)     Corrugations   
(b)     Fins
(c)     Tubes   
(d)     Radiator tanks
(e)    All of the above
Ans: e

67.    Transformers with a capacity of upto _____ have a cooling radiator system with natural cooling
(a)     2 MVA   
(b)     5 MVA
(c)     7.5 MVA   
(d)     10 MVA
Ans: d

68.    The forced oil and air circulation method is usual one for transformers of capacities
(a)     upto 5 MVA     
(b)     upto 10 MVA
(c)    upto 20 MVA
(d)    30 MVA upwards
Ans: d

69.    The flash point of transformer oil should be higher than
(a)   40°C   
(b)   60°C
(c)   80°C   
(d)   104°C
Ans: d

70.    The voltage control in electric supply networks in required on account of which of the following reasons ?
(a)     Adjustment of voltage at consumers premises within statutory limits
(b)     Control of active and reactive power
(c)    Adjustment of short period daily and seasonal voltage variations in accordance with variations of load
(d)    All of the above
Ans: d

71.    D.C. windings are
(a)    sometimes 2-layer type
(b)    never 2-layer type
(c)    always 2-layer type
(d)    none of the above
Ans: c

72.    The usual values of maximum flux densities for distribution transformers using hot rolled silicon steel are
(a)     0.5 to 0.8 Wb/m2
(b)     0.8 to 1.0 Wb/m2
(c)    1.1 to 1.35 Wb/m2
(d)    1.4 to 1.8 Wb/m2
Ans: c

73.    For 275 kV transformers, using cold rolled grain oriented steel, which of the following values of flux density may be used?
(a)     1.0 Wb/m2   
(b)     1.1 Wb/m2
(c)     1.3 Wb/m2   
(d)     1.6 Wb/m2
(e)    None of the above
Ans: d

74.    For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used ?
(a)    1.0 to 1.2 A/mm2
(b)    1.5 to 2.0 A/mm2
(c)    2.2 to 3.2 A/mm2
(d)    3.2 to 4.2 A/mm2
Ans: c

75.    A current density of _____ is ilsed for large power transformers with forced circulation of oil or with water cooling coils
(a)     1.5 to 2.5 A/mm2
(b)     3.5 to 4.5 A/mm2
(c)    4.0 to 5.0 A/mm2
(d)    5.4 to 6.2 A/mm2
Ans: d

76.    The high voltage winding is usually which of the following type ?
(a)    Cylindrical winding with circular conductors
(b)    Cross-over winding with either circular or small rectangular conductors
(c)    Continuous disc type winding with rectangular conductors
(d)    All of the above types
Ans: d

77.    Which of the following is the basic consideration in the design of insulation ?
(a)     Electrical considerations
(b)     Mechanical considerations
(c)    Thermal considerations
(d)    All of the above
Ans: d

78.    A practical formula for determining the thickness of insulation between low voltage and high voltage windings is
(a)    1 + 0.2 kVmm
(6)    2 + 0.5 kVmm
(c)    4 + 0.7 kV mm 
(d)    5 + 0.9 kV mm
Ans: d

79.    The insulation between windings and grounded core and the insulation between the windings of the same phase is called
(a)    minor insulation
(b)    major insulation
(c)    either of the above
(d)    none of the above
Ans: b

80.    The cylindrical windings using circular conductors are used for current rating of
(a)    upto 20 A   
(b)    upto 40 A
(c)    upto 60 A   
(d)    upto 80 A
Ans: d

81.    The surge phenomenon is particularly important in case of
(a)    low voltage transformers
(b)    medium voltage transformers
(c)    high voltage transformers
(d)    any of the above
Ans: c

82.    Which of the following in an application of D.C. motors?
(a)     Traction
(b)     Drives for process industry
(c)    Battery driven vehicles
(d)    Automatic control
(e)    All of the above
Ans: e

83.    D.C. servomotors are used in
(a)     purely D.C. control systems
(6)     purely AC. control systems
(c)    both D.C. and AC. control systems
(d)    none of the above
Ans: a

84.    The stator of a D.C. machine comprises of
(a)    main poles   
(6)    interpoles
(c)    frame   
(d)    all of the above
Ans: d

85.    The laminations of the armature of a D.C. machine are usually _____ thick.
(a)    0.1 to 0.2 mm  
(b)    0.2 to 0.3 mm
(c)    0.3 to 0.4 mm   
(d)    0.4 to 0.5 mm
Ans: d

86.    is usually used for brush rockers
(a)     Mild steel   
(b)     Copper
(c)     Aluminium      
(d)     Cast-iron
Ans: d

87. ______ brushes are fragile and cause excessive wear of commutator,
(a)     Natural graphite
(b)     Hard carbon
(c)     Electro graphitic
(d)     Metal graphite
Ans: a

88.   Which of the following brushes can be used for high values of current density ?
(a)    Metal graphite brushes
(b)    Hard carbon brushes
(c)    Electro-graphitic brushes
(d)    Natural graphite brushes
Ans: a

89    ________ is the common method of applying brushes to the commntator.
(a)     Radial   
(b)     Trailing
(c)     Reaction   
(d)     All of the above
Ans: d

90.    Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?
(a)     Increased I R losses
(b)     Increased core losses
(c)    Poor commutation
(d)    Change in motor parameters
(e)    All of the above
Ans: e

91.    The weight of copper of both armature and field windings decreases with _____ in number of poles.
(a)     increase   
(b)     decrease
(c)    either of the above
(d)    none of the above
Ans: a

92.    In a D.C. machine the number of brush arms is _____ the number of poles.
(a)     less than   
(b)     equal to
(c)    greater than
(d)    none of the above
Ans: b

93.    In a D.C. machine the current per brush arm should not be more than
(a)     100 A   
(6)     200 A
(e)    300 A   
(d)     400 A
Ans: d

94.    In a D.C. machine, the value of peripheral speed should not, normally, exceed
(a)     10 m/s   
(b)     20 m/s
(c)     30 m/s   
(d)     40 m/s
Ans: c

95.    In D.C. machines the width of the duct is usually
(a)     4 mm   
(b)     6 mm
(c)     8 mm   
(d)     10 mm
Ans: d

96.    D.C. machines designed with a large value of air gap length have
(a)    worst, ventilation
(b)    poor ventilation
(c)    better ventilation
(d)    none of the above
Ans: c

97.    In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made
(a)    equal to that of armature mmf
(b)    less in comparison with the arma¬ture mmf
(c)    large in comparison with the arma-ture mmf
(d)    none of the above
Ans: c

98.    In D.C. machines, the ____ in field mmf results in increase in size and cost of machines.
(a)     increase   
(b)     decrease
(c)    either of the above
(d)    none of the above
Ans: a

99.    The operation of a D.C. machine with large air gap lengths is comparatively
(a)     quiet   
(b)     noisy
(c)     either of the above
(d)     none of the above
Ans: a

100.    Which of the following methods may be adopted to reduce the effects of armature reaction ?
(a)    Increase in length of air gap at pole tips
(b)    Increasing reluctance of pole tips
(c)    Compensating windings
(d)     Interpoles
(e)    All of the above
Ans: e

101.    In D.C. machines the usual limit of slot pitch is
(a)     between 5 to 10 mm
(b)     between 10 to 15 mm
(c)    between 15 to 20 mm
(d)    between 25 to 35 mm
Ans: d

102.    In D.C. machines the number of slots per pole usually lies
(a)     between 2 to 4 
(b)     between 6 to 8
(c)    between 9 to 16
(d)    between 20 to 30
Ans: c

EEE MCQ (Electrical Engineering Materials)

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Electrical Engineering Materials Multiple Choice Questions and Answers Preparation for Competition exams

1.    The converse of hardness is known as
(a)     malleability     
(b)     toughness
(c)    softness
(d)    none of the above
Ans: c

2.    On which of the following factors does the resistivity of a material depend ?
(a)    Resistance of the conductor
(b)    Area of the conductor section
(c)    Length of the conductor
(d)    All of the above
Ans: d

3.     is a negatively charged particle present in an atom.
(a)     Proton   
(b)     Neutron
(c)    Electron
(d)    None of the above
Ans: c

4.    The formula ____ determines the number of electrons that can be accommodated in any level.
(a)     2n2   
(6)     4n2
(c)     2n3   
(d)     4ns
Ans: a

5.    The tiny block formed by the arrangement of a small group of atoms is called the
(a)     unit cell   
(b)     space lattice
(c)    either (a) or (b)
(d)    none of the above
Ans: a
6.   The co-ordination number of a simple cubic structure is
(a)     2   
(b)     4
(c)     6   
(d)     8
Ans: c

7.   The covalent bond is formed by
(a)     transfer of electrons between atoms
(b)     sharing of electrons between atoms
(e)     sharing of variable number of electrons by a variable number of atoms
(d)     none of the above
 Ans: b

8.    A perfect conductor has
(a)     zero conductivity
(b)     unity conductivity
(c)    infinite conductivity
(d)    none of the above
Ans: c

9.    The metal having the lowest temperature coefficient of resistance is
(a)     gold   
(b)     copper
(c)     aluminium   
(d)     kanthal
Ans: a

10.    Commonly used conducting materials are
(a)     copper   
(b)     aluminium
(c)    both (a) and (b)
(d)    copper and silver
(e)    platinum and gold
Ans: c

11.    Which of the following materials is preferred for transmitting electrical energy over long distance ?
(a)     Copper   
(b)     Aluminium
(c)    Steel reinforced copper
(d)    Steel reinforced aluminium
Ans: d

12.    The kinetic energy of a bounded electron is
(a)     less than that of unbounded electron
(6)     greater than that of unbounded electron
(c)    equal to that of unbounded electron
(d)    infinite
(e)    none of the above
Ans: a

13.    A highly conductive material must have
(a)     highest conductivity
(b)     lowest temperature co-efficient
(c)    good mechanical strength
(d)    good corrosion resistance
(e)    easy solderable and drawable quality
(f)     all of the above
Ans: f

14.    The conductivity of a conductor can be increased by
(a)     decreasing its temperature
(b)     increasing its temperature
(c)    decreasing its vibration
(d)    increasing its vibration
Ans: a

15.    Superconductivity is observed for
(a)    infrared frequencies
(b)    d.c. and low frequency
(c)    a.c. and high frequency
(d)    frequencies having no effect
(e)    none of the above
Ans: b

16.    The superconductivity is due to
(a)    the crystal structure having  no atomic vibration at 0°K
(b)    all electrons interact in the super-conducting state
(c)    the electrons jump into nucleus at 0°K
(d)    none of the above
Ans: a

17.    The value of critical field below the transition temperature will
(a)     increase   
(b)     decrease
(c)    remain unchanged
(d)    any of the above
Ans: a

18.    In a superconductor the value of critical density depends upon
(a)     magnetic field strength  
(b)     temperature
(c)     either (a) or (b)
(d)     both (a) and (b)
Ans: d

19.    Superconductors are becoming popular for use in
(a)    generating very strong magnetic field
(b)    manufacture of bubble memories
(c)    generating electrostatic field
(d)    generating regions free from magnetic field
Ans: a

20.    High resistivity materials are used in
(a)     precision instruments
(6)     heating elements
(c)    motor starters
(d)    incandescent lamps
(e)    all of the above
Ans: e

21.    Mercury as an electric contact material is
(a)     a liquid   
(b)     a metal
(c)     a metal liquid   
(d)     a gas
 Ans: c

22.    An H.R.C. fuse is
(a)     a ceramic body having metal and caps
(b)     a wire of platinum
(c)    a heavy cross-section of copper or aluminium
(d)    a ceramic tube having carbon rod inside it
Ans: a

23.    Which of the following resistive materials has the lowest temperature co-efficient of resistance ?
(a)     Nichrome   
(b)     Constantan
(c)     Kanthal   
(d)     Molybdenum
Ans: a

24.    The coils of D.C. motor starter are wound with wire of
(a)     copper   
(b)     kanthal
(c)     manganin   
(d)     nichrome
Ans: c

25.    The conductors have transport phenomena of electrons due to
(a)     electric field     
(b)     magnetic field
(c)    electromagnetic field
(d)    none of the above
Ans: a

26.    The transition temperature of mercury is
(a)     18.0°K   
(6)     9.22°K
(c)     4.12°K   
(d)     1.14'K
Ans: c

27.    By increasing impurity content in the metal alloy the residual resistivity always
(a)     decreases   
(b)     increases
(c)    remains constant
(d)    becomes temperature independent
Ans: b

28.    The structure sensitive property of a super conductor is
(a)     critical magnetic field
(b)     transition temperature
(c)    critical current density
(d)    none of the above
Ans: c

29.    At transition temperature the value of critical field is
(a)     zero
(6)     negative real value
(c)    positive real value
(d)    complex value
Ans: a

30.    Which of the following variety of copper has the best conductivity ?
(a)    Induction hardened copper
(b)    Hard drawn copper
(c)    Pure annealed copper   
(d)    Copper containing traces of silicon
Ans: c

31.    Constantan contains
(a)     silver and tin
(b)     copper and tungsten   
(c)    tungsten and silver
(d)    copper and nickel
Ans: d

32.    Which of the following is the poorest conductor of electricity ?
(a)     Carbon   
(b)     Steel
(c)     Silver   
(d)     Aluminium
Ans: a

33    ______ has zero temperature co-efficient of resistance.
(a)     Aluminium       
(b)     Carbon
(c)     Porcelain   
(d)     Manganin
Ans: d

34.    Piezoelectric materials serve as a source of _____ .   
(a)     resonant waves
(b)     musical waves
(c)     microwaves       
(d)     ultrasonic waves
Ans: d

35.    In thermocouples which of the following pairs is commonly used ?
(a)     Copper-constantan
(b)     Aluminium-tin   
(c)    Silver-German silver
(d)    Iron-steel
Ans: a

36    is viscoelastic.
(a)     Cast-iron   
(6)     Graphite   
(c)     Rubber   
(d)     Glass
Ans: c

37.    Carbon electrodes are not used in
(a)    GLS lamps
(b)    electric arc furnace   
(c)    dry cells
(d)    cinema projectors
Ans: a

38.    Solder is an alloy of
(a)    copper and aluminium   
(b)    tin and lead
(c)    nickel, copper and zinc
(d)    silver, copper and lead
Ans: b

39    ______ is most commonly used for making magnetic recording tape   
(a)     Silver nitrate
(b)     Ferric oxide
(c)    Small particles of iron
(d)    Silicon-iron
Ans: b

40.   Overhead telephone wires are made of
(a)     aluminium       
(b)     steel   
(c)     ACSR conductors
(d)     copper
 Ans: b

41. ______ is an example of piezoelectric material.
(a)     Glass   
(b)     Quartz
(c)     Corrundum      
(d)     Neoprene
Ans: b

42. _____ is the main constituent of glass
(a)     Fe203   
(b)     Si02
(c)     AI2O3   
(d)     B2O3
Ans: b

43. A good electric contact material should have all of the following properties excePt
(a)    high resistivity
(b)    high resistance to corrosion
(c)    good thermal conductivity
(d)    high melting point
Ans: a

44. Most of the common metals have _____ structure.
(a)     linear   
(b)     hexagonal
(c)     orthorhombic    
(d)     cubic
Ans: d

45. Which of the following affect greatly the resistivity of electrical conductors ?
(a)     Composition     
(b)     Pressure
(c)     Size   
(d)     Temperature
Ans: a

46. Thermonic emission occurs in
(a)     vacuum tubes
(b)     copper conductors
(c)     ferrite cores      
(d)     transistors
Ans: a

47. _____ is a hard solder.
(a)     Tin-lead   
(6)     Tin-silver-lead
(c)    Copper-zinc
(d)    None of the above
Ans: c

48. Addition of 0.3 to 4.5% silicon to iron _____ the electrical resistivity of iron.
(a)     increases   
(b)     decreases
(c)     does not change
Ans: a

49. Super conductivity can be destroyed by
(a)    adding impurities
(b)    reducing temperatures
(c)    application of magnetic field
(d)    any of the above
Ans: c

50.     Non-linear resistors
(a)     produce harmonic distortion
(b)     follows Ohm's law at low tempera¬tures only
(c)    result in non-uniform heating
(d)    none of the above
Ans: a

51. A carbon resistor contains
(a)     carbon crystals
(b)     solid carbon granules
(c)    pulverized coal
(d)    finely divided carbon black.
Ans: d

52.    Which of the following materials does not have covalent bonds ?
(a)    Organic polymers
(b)    Silicon   
(c)     Metals
Ans: c

53.    In graphite, bonding is
(a)     covalent   
(b)     metallic
(c)    Vander Waals
(d)    Vander Waals and covalent
Ans: d

54.    Total number of crystal systems is
(a)     2   
(b)     4
(c)     7   
(d)     12
Ans: c

55.    The number of atoms per unit cell in B.C.C. structure is
(a)     1   
(b)     2
(c)     4   
(d)     8
Ans: b

56.    The conductivity of a metal is determined by
(a)     the electronic concentration and the mobility of the free electrons
(6)     the number of valence electrons per atom
(c)    either (a) or (b)
(d)    none of the above
Ans: a

57.    The resistivity of a metal is a function of temperature because
(a)     the amplitude of vibration of the atoms varies with temperature
(b)     the electron density varies with temperature
(c)     the electron gas density varies with temperature
Ans: a

58.    In a crystal, an atom vibrates at a frequency determined by
(a)    the heat content of the crystal
(b)    the temperature of the crystal
(c)    the stiffness of the bonds it makes with neighbours
Ans: c

59.    Due to which of the following reasons aluminium does not corrode in atmost phere ?
(a)     Aluminium is a noble metal
(b)     Atmospheric oxygen can only diffuse very slowly through the oxide layer which is formed on the surface of aluminium
(c)     No reaction with oxygen occurs ft Any of the above
 Ans: b

60.    The impurity atoms is semiconductors
(a)     inject more charge carriers
(6)     reduce the energy gap
(c)    increase the kinetic energy of valence electrons
(d)    all of the above
Ans: b

61.    Which of the following material is not a semiconductor ?
(a)     Silica   
(b)     Germanium
(c)     Selenium   
(d)     Gallium-arsenide
Ans: a

62.    Carbon resistors are used extensively because they are
(a)     easy to make    
(b)     compact
(c)    inexpensive
(d)    all of the above reasons
Ans: d

63.    Carbon rods are used in wet and dry cells because
(a)     carbon rod serves as conductor
(b)     carbon can resist the attack of bat¬tery acid
(c)    both (a) and (b)
(d)    either (a) or (b)
Ans: c

64.    Due to which of the following factors the brush wear rate is altered ?
(a)     Speed of the machine
(b)     Contact pressure
(c)    Surface conditions of brush and commutator
(d)    Excessive sparking
(e)    All of the above
Ans: e

65.    Which of the following are non-conductors of electricity?
(a)     Non-metal solids except carbon
(b)     Air and most other gases
(c)    Pure water and liquids in general except mercury
(d)    All of the above
Ans: d

66.    Carbon bearings are used under which of the following conditions ?
(a)    Where lubrication is difficult or im-possible
(b)    Where corrosive chemical action exists
(c)    Where high temperature exists
(d)     All of the above
Ans: d

67. Which of the following high resistance materials has the highest operating temperature ?
(a)     Kanthal   
(b)     Manganin
(c)     Nichrome   
(d)     Eureka
Ans: a

68.    Steel wire is used as
(a)     overhead telephone wire
(b)     earth wire
(c)    core wire of ACSR
(d)    all of the above 
Ans: d

69.    Low resistivity materials are used in
(a)    transformer, motor and generator windings
(b)    transmission and distribution lines
(c)    house wiring
(d)    all above applications
Ans: d

70.    Platinum is used in
(a)    electrical contacts
(b)    thermocouple
(c)    heating element in high temperature furnace
(d)    grids of special purpose vacuum tubes
(e)    all of the above
Ans: e

71.    Which of the following is an advantage of stranded conductor over equivalent single conductor ?
(a)     Less liability to kink
(b)     Greater flexibility
(c)    Less liability to break
(d)    All of the above
Ans: d

72.    Due to which of the following reasons copper and aluminium are not used for heating elements ?
(a)    Both have great tendency for oxidation
(b)    Both have low melting point
(c)    Very large length of wires will be required
(d)    All of the above
Ans: d

73.    Copper, even though costly, finds use in the windings of electrical machines because
(a)     copper points offer low contact resistance
(b)     copper can be easily soldered and welded
(e)    copper windings are less bulky and the machines become compact
(d)     all of the above
 Ans: d

74.    Which of the following materials is used for making coils of standard resistances ?
(a)     Copper   
(b)     Nichrome
(c)     Platinum   
(d)     Manganin
Ans: d

75.    Substances whose specific resistance abruptly decreases at very low temperature are called
(a)     insulators   
(b)     conductors
(c)     semiconductors
(d)     superconductors
Ans: d

76.    Which of the following materials is the best conductor of electricity ?
(a)    Tungsten   
(b)    Aluminium
(c)    Copper   
(d)    Carbon
Ans: c

77.     is the property of absorbing moisture from atmosphere.
(a)    Solubility   
(b)    Viscosity
(c)    Porosity   
(d)    Hygroscopicity
Ans: d

78.    Thermocouples are mainly used for the measurement of
(a)     temperature    
(b)     resistance
(c)     eddy currents
(d)    coupling co-efficient
Ans: a

79.    Due to which of the following fact, in India, aluminium is replacing copper ?
(a)     Aluminium is more ductile and malleable than copper
(6)     Aluminium is available in plenty, cheaper and lighter than copper
(c)    Aluminium has lower resistivity than that of copper
(d)    Aluminium has less temperature co-efficient than copper
Ans: b

80.    The conduction of electricity, in semiconductors, takes place due to movement of
(a)     positive ions only
(b)     negative ions only
(c)    positive and negative ions
(d)    electrons and holes
Ans: d

81.    Which of the following is a semiconductor material ?
(a)     Phosphorous    
(b)     Rubber
(c)     Silicon   
(d)     Aluminium
Ans: c

82.    Selenium is _____ semiconductor.
(a)     extrnisic   
(b)     intmisic
(c)     N-type   
(d)     P-type
Ans: b

83.    ________ has the best damping properties.
(a)     Diamond   
(b)     High speed steel
(c)     Mild steel   
(d)     Cast iron
Ans: d

84.    The photo-electric effect occurs only when the incident light has more than a certain critical
(a)     intensity   
(b)     speed
(c)     frequency   
(d)     wave length
Ans: c

85.    If the resistance of a conductor does not vary in accordance with Ohm's law it is known as
(a)    non-linear conductor
(b)    reverse conductor
(c)    bad-conductor  
(d)     non-conductor
Ans: a

86.    Spark plug makes use of which of the following materials for insulation ?
(a)     Porcelain   
(b)     Slate
(c)     Asbestos   
(d)     Glass
Ans: a

87.    The forbidden gap in an insulator is
(a)     large   
(b)     small
(c)     nil
(d)     any of the above
Ans: a

88.    Which of the following factors affect resistivity of metals ?
(a)     Age hardening
(b)     Alloying
(c)     Temperature    
(d)     Cold work
(e)     All of the above
Ans: e

89.    Effect of moisture on the insulating materials is to
(a)     decrease dielectric constant
(b)     decrease dielectric strength
(c)    decrease insulation resistance
(d)    increase dielectric loss
(e)    all of the above
Ans: e

90.    Surface resistance of an insulating material is reduced due to the
(a)     smoky and dirty atmosphere
(b)     humidity in the atmosphere
(c)    both (a) and (b)
(d)    neither (a) nor (b)
Ans: c

91.    Superconducting metal in super conducting state has relative permeability of
(a)     zero   
(b)     one
(c)     negative   
(d)     more than one
Ans: a

92.    In conductors conduction of electricity takes place due to movement of
(a)    electrons only
(b)    positive ions only
(c)    negative ions only
(d)    positive and negative ions
(e)    none of the above
Ans: a

93.    The carbon percentage is least in
(a)    low carbon steel
(b)    wrought iron
(c)    cast iron   
(d)     malleable iron
Ans: b

94.    For a particular material the Hall coefficient was found to be zero. The material is
(a)     insulator   
(6)     metal
(c)     intrinsic semiconductor
(d)     none of the above
Ans: b

95.    The conductivity of an extrinsic semiconductor with temperature
(a)     decreases   
(b)     increases
(c)     remains constant
Ans: c

96.    The current due to electron flow in conduction band is    the hole current in valence band.
(a)     equal to   
(b)     less than
(c)     greater than
(d)     any of the above
Ans: c

97.    For a hole which of the following statements is incorrect ?
(a)     Holes can exist in certain semicon-ductors only
(b)     Holes can exist in any material in-cluding conductors
(c)     Holes may constitute an electric current
(d)     Holes can be considered as a net positive charge
Ans: b

98.     is an element used in semiconductors whose atoms have three valence electrons.
(a)     An acceptor      
(b)     A donor
(c)     Germanium      
(d)     Silicon
Ans: a

99.    The minority carrier concentration is largely a function of
(a)    forward biasing voltage
(b)    reverse biasing voltage
(c)    temperature
(d)    the amount of doping
Ans: c

100.   For germanium the forbidden energy gap is
(a)    0.15 eV   
(b)    0.25 eV
(C)    0.5eV   
(d)    0.7eV
 Ans: d

EEE MCQ (Electrolysis and Storage of Batteries)

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Electrolysis and Storage of Batteries - Electrical engineering multiple choice questions and answers for competitive exams

1. "The mass of an ion liberated at an electrode is directly proportional to the quantity of electricity".
The above statement is associated with
(a) Newton's law
(b) Faraday's law of electromagnetic
(c) Faraday's law of electrolysis
(d) Gauss's law

Ans: c

2. The charge required to liberate one gram equivalent of any substance is known as ______ constant
(a) time
(b) Faraday's
(c) Boltzman

Ans: b

3. During the charging of a lead-acid cell
(a) its voltage increases
(b) it gives out energy
(c) its cathode becomes dark chocolate brown in colour
(d) specific gravity of H2SO4 decreases

Ans: a

4. The capacity of a lead-acid cell does not depend on its
(a) temperature    
(b) rate of charge
(c) rate of discharge
(d) quantity of active material

Ans: b

5. During charging the specific gravity of the electrolyte of a lead-acid battery
(a) increases
(b) decreases
(c) remains the same
(d) becomes zero

Ans: a

6. The active materials on the positive and negative plates of a fully charged lead-acid battery are
(a)     lead and lead peroxide
(b)     lead sulphate and lead
(c) lead peroxide and lead
(d) none of the above
Ans: c

7. When a lead-acid battery is in fully charged condition, the colour of its positive plate is
(a) dark grey
(b) brown
(c) dark brown      
(d) none of above
Ans: c

8. The active materials of a nickel-iron battery are
(a)     nickel hydroxide
(6)     powdered iron and its oxide
(c) 21% solution of KOH
(d) all of the above
Ans: d

9. The ratio of ampere-hour efficiency to watt-hour efficiency of a lead-acid cell is
(a) just one
(b) always greater than one
(c) always less than one
(d) none of the above.
Ans: b

10. The best indication about the state of charge on a lead-acid battery is given by
(a) output voltage
(b) temperature of electrolyte
(c) specific gravity of electrolyte
(d) none of the above
Ans: c

11. The storage battery generally used in electric power station is
(a) nickel-cadmium battery
(b) zinc-carbon battery
(c) lead-acid battery
(d) none of the above
Ans: c

12. The output voltage of a charger is
(a) less than the battery voltage
(b) higher than the battery voltage
(c) the same as the battery voltage
(d) none of the above
Ans: b

13. Cells are connected in series in order to
(a)     increase the voltage rating
(6)     increase the current rating
(c) increase the life of the cells
(d) none of the above
Ans: a

14. Five 2 V cells are connected in parallel.
The output voltage is
(a) 1 V
(6) 1.5 V
(c) 1.75 V
(d) 2 V
Ans: d

15. The capacity of a battery is expressed in terms of
(a)     current rating
(b)     voltage rating
(e) ampere-hour rating
(d) none of the above
Ans: c

16. Duringthe charging and discharging of a nickel-iron cell
(a) corrosive fumes are produced
(b) water is neither formed nor absorbed
(c) nickel hydroxide remains unsplit
(d)     its e.m.f. remains constant
Ans: b

17. As compared to constant-current system, the constant-voltage system of charging a lead acid cell has the advantage of
(a) reducing time of charging
(b) increasing cell capacity
(c) both (a) and (b)
(d) avoiding excessive gassing
Ans: c

18. A dead storage battery can be revived by
(a) adding distilled water
(6) adding so-called battery restorer
(c) a dose of H2SO4
(d) none of the above
Ans: d

19. As compared to a lead-acid cell, the efficiency of a nickel-iron cell is less due to its
(a) compactness
(b) lower e.m.f.
(c) small quantity of electrolyte used
(d) higher internal resistance
Ans: d

20. Trickle charging of a storage battery helps to
(a)     maintain proper electrolyte level
(b)     increase its reserve capacity
(c) prevent sulphation
(d) keep it fresh and fully charged
Ans: d

21. Those substances of the cell which take active part in chemical combination and hence produce electricity during
charging or discharging are known as______materials.
(a) passive
(b) active
(c) redundant
(d) inert
Ans: b

22. In a lead-acid cell dilute sulphuric acid (electrolyte) approximately comprises the following
(a) one part H2O, three parts H2SO4
(b) two parts H2O, two parts H2SO4
(c) three parts H2O, one part H2SO4
(d) all H2S04
Ans: c

23. It is noticed that durmg charging
(a)     there is a rise in voltage
(6)     energy is absorbed by the cell
(c) specific gravity of H2SO4 is increased
(d) the anode becomes chocolate brown in colour (PbCfe) and cathode be¬comes grey metallic lead (Pb)
(e) all of the above
Ans: e

24. It is noticed that during discharging the following does not happen
(a)     both anode and cathode become PbS04
(b)     specific gravity of H2SO4 decreases
(c) voltage of the cell decreases
(d) the cell absorbs energy
Ans: d

25. The ampere-hour efficiency of a leadacid cell is normally between
(a) 20 to 30%
(b) 40 to 50%
(c) 60 to 70%
(d) 90 to 95%
 Ans: d

26. The watt-hour efficiency of a lead-acid cell varies between
(a) 25 to 35%
(b) 40 to 60%
(c) 70 to 80%
(d) 90 to 95%
Ans: c

27. The capacity of a lead-acid cell is measured in
(a) amperes
(b) ampere-hours
(c) watts
(d) watt-hours
Ans: b

28. The capacity of a lead-acid cell depends on
(a) rate of discharge
(b) temperature
(c) density of electrolyte
(d) quantity of active materials
(e) all above
Ans: e

29. When the lead-acid cell is fully charged, the electrolyte assumes _____ appearance
(a) dull
(b) reddish
(c) bright
(d) milky
Ans: d

30. The e.m.f. of an Edison cell, when fully charged, is nearly
(a) 1.4 V
(b) 1 V
(c) 0.9 V
(d) 0.8 V
Ans: a

31. The internal resistance of an alkali cell is nearly _____ times that of the lead-acid cell.
(a) two
(b) three
(c) four
(d) five
Ans: d

32. The average charging voltage for alkali cell is about
(a) 1 V
(b) 1.2 V
(c) 1.7 V
(d) 2.1 V
Ans: c

33. On the average the ampere-hour efficiency of an Edison cell is about
(a) 40%
(b) 60%
(c) 70%
(d) 80%
Ans: d

34. The active material of the positive plates of silver-zinc batteries is
(a) silver oxide      
(b) lead oxide
(c) lead
(d) zinc powder
Ans: a

35. Lead-acid cell has a life of nearly charges and discharges
(a) 500
(b) 700
(c) 1000
(d) 1250
Ans: d

36. Life of the Edison cell is at least
(a) five years
(b) seven years
(c) eight years
(d) ten years
Ans: a

37. The internal resistance of a lead-acid cell is _____ that of Edison cell
(a)    less than
(b)    more than
(c) equal to
(d) none of the above
Ans: a

38. Electrolyte used in an Edison cell is
(a) NaOH
(b) KOH
(c) HC1
(d) HN03
Ans: b

39. Electrolyte used in a lead-acid cell is
(a) NaOH
(b) onlyH2S04
(c) only water        
(d) dilute H2SO4
Ans: d

40. Negative plate of an Edison cell is made of
(a) copper
(b) lead
(c) iron
(d) silver oxide
Ans: c

41. The open circuit voltage of any storage cell depends wholly upon
(a) its chemical constituents
(b) on the strength of its electrolyte
(c) its temperature      
(d) all above
Ans: d

42. The specific gravity of electrolyte is measured by
(a) manometer
(6) a mechanical gauge
(c) hydrometer      
(d) psychrometer
Ans: c

43. When the specific gravity of the electrolyte of a lead-acid cell is reduced to 1.1 to 1.15 the cell is in
(a) charged state
(b) discharged state
(c) both (a) and (b)
(d) active state
Ans: b

44. In ______ system the charging current is intermittently controlled at either a maximum or minimum value
(a)     two rate charge control
(b)     trickle charge
(c) floating charge
(d) an equalizing charge
Ans: a

45. Over charging
(a) produces excessive gassing
(b) loosens the active material
(e) increases the temperature resulting in buckling of plates
(d)     all above
Ans: d

46. Undercharging
(a)     reduces specific gravity of the electrolyte
(b)     increases specific gravity of the electrolyte
(c) produces excessive gassing
(d) increases the temperature
Ans: a

47. Internal short circuits are caused by
(a)     breakdown of one or more separators
(b)     excess accumulation of sediment at the bottom of the cell
(c) both (a) and (b)
(d) none of the above
Ans: c

48. The effect of sulphation is that the internal resistance
(a) increases
(b) decreases
(c) remains same
(d) none of the above
Ans: a

49. Excessive formation of lead sulphate on the surface of the plates happens because of
(a)     allowing a battery to stand in discharged condition for a long time
(b)     topping up with electrolyte
(c) persistent undercharging
(d) low level of electrolyte
(e) all above
Ans: e

50. The substances which combine together to store electrical energy during the charge are called ______ materials
(a) active
(b) passive
(c) inert
(d) dielectric
Ans: a

51. In a lead-acid cell, lead is called as
(a) positive active material
(b) negative active material
(c)     passive material
(d) none of the above
Ans: b

52. The lead-acid cell should never be discharged beyond
(a) 1.8 V
(b) 1.9 V
(c) 2 V
(d) 2.1 V
Ans: a

53. On overcharging a battery
(a)     it will bring about chemical change in active materials
(b)     it will increase the capacity of the battery
(c) it will raise the specific gravity of the electrolyte
(d) none of the above will occur
Ans: d

54. Each cell has a vent cap
(a)     to allow gases out when the cell is on charge
(b)     to add water to the cell if needed
(c) to check the level of electrolyte
(d) to do all above functions
Ans: d

55. Following will occur if level of electrolyte falls below plates
(a) capacity of the cell is reduced
(b) life of the cell is reduced
(c) open plates are converted to lead sulphate
(d) all above
Ans: d

56. In constant voltage charging method, the charging current from discharged to fully charged condition
(a)     decreases
(b)     increases
(c) remains constant
(d) none of the above
Ans: a

57. 48 ampere-hour capacity would deliver a current of
(a)     48 amperes for 1 hour
(b)     24 amperes for 2 hours
(c) 8 amperes for 6 hours
(d) 6 amperes for 8 hours
Ans: d

58. In constant-current charging method, the supply voltage from discharged to
fully charged condition
(a)     decreases
(b)     increases
(c) remains constant
(d) none of the above
Ans: b

59. Battery charging equipment is generally installed
(a)     in well ventilated location
(b)     in clean and dry place
(c) as near as practical to the battery being charged
(d) in location having all above features
Ans: d

60. Following will happen if the specific gravity of electrolyte becomes more than 1.23.
(a)     Loss of capacity
(b)     Loss of life
(c) Corrosion of the grids of the plate
(d) All above
Ans: d

61. Batteries are charged by
(a) rectifiers
(b) engine generator sets
(c) motor generator sets
(d) any one of the above methods
 Ans: d

62. Cell short circuit results in
(a) low sp. gravity electrolyte
(b) abnormal high temperature
(c) reduced gassing on charge
(d) all above
Ans: d

63. Internal resistance of a cell is reduced by
(a) using vent plug to permit gas formed during discharge
(b) increasing the plate area
(c) putting plates very close together
(d) all above methods
Ans: d

64. Capacity of dry cells is
(a) more when it is supplying current for intermittent periods
(b) more when it is supplying current for continuous periods
(c) unaffected by the type of discharge
(d) none of the above
Ans: a

65. Battery container should be acid resistance, therefore it is made up of
(a) glass
(b) plastic
(c) wood
(d) all above
Ans: d

66. Sulphated cells are indicated by
(a)     the loss of capacity of the cell
(6)     the decrease of the specific gravity
(c) the low voltage of the cell on discharge
(d) all above conditions
Ans: d

67. In a lead-acid cell, if the specific gravity of sulphuric acid is 1.8, it will require following ratio of acid to water to get mixture of specific gravity of 1.3
(a)     6 parts of acid to 4 parts of water
(b)     4 parts of acid to 4 parts of water
(c) 4 parts of acid to 6 parts of water
(d) 4 parts of acid to 8 parts of water
Ans: c

68. Local action in a battery is indicated by
(a) excessive gassing under load conditions
(b) excessive drop in the specific gravity of electrolyte even when the cell is on open circuit
(c) both (a) and (b)
(d) none of the above
Ans: d

69. Following will happen if battery charging rate is too high
(a) excessive gassing will occur
(b) temperature rise will occur
(c) bulging and buckling of plates will occur
(d) all above will occur
Ans: d

70. Internal resistance of a cell is due to
(a) resistance of electrolyte
(b) electrode resistance
(c)     surface contact resistance between electrode and electrolyte
(d) all above
Ans: d

71. If a battery is wrongly connected on charge following will happen
(a) current delivered by the  battery will be high
(b) current drawing will be nil
(c) current drawing will be very small
(d) current drawing will be very high
Ans: d

72. In order that a hydrometer may float vertically in electrolyte its C.G. should be
(a)     lowered
(b)     raised
(c) undisturbed
(d) displaced sideways
Ans: a

73. If a lead-acid cell is discharged below 1.8 V the following will happen.
(a) Capacity of cell will reduce
(b) Sulphation of plates will occur
(c) Internal resistance will increase
(d) All above will occur
Ans: d

74. Life of the batteries is in the following ascending order.
(a) Lead-acid cell, Edison cell, Nickel cadmium cell
(b) Lead-acid cell, Nickel-cadmium cell, Edison cell
(c) Edison cell, Nickel-cadmium cell, lead-acid cell
(d) Nickel-cadmium cell, Edison cell, lead-acid cell
Ans: a

75. Persons preparing electrolyte should wear
(a) goggles or other face shield
(b) rubber
(c) rubber boots and gloves
(d) all above safety devices
Ans: d

76. Excessive charging a battery tends to
(a) produce gassing
(b) increase the internal resistance of the battery
(c) to corrode the positive plates into lead peroxide thereby weakening them physically
(d) bring about all above changes
Ans: d

77. Shelf life of a small dry cell is
(a)     equal to that of large dry cell
(6)     less than that of large dry cell
(c) more than that of large dry cell
(d) none of the above
Ans: b

78. The current flow through electrolyte is due to the movement of
(a)     ions
(b)     holes
(c) electrons
(d) none of the above
Ans: a

79. Level of electrolyte in a cell should be _____ the level of plates
(a)     below
(b)     equal to
(c) above
(d) none of the above
Ans: c

80. During discharge, the active material of both the positive and negative plates is changed to
(a) Pb
(b) Pb02
(c) PbO
(d) PbS04
Ans: d

81 of electrolytelndicates the state of charge of the battery
(a) colour
(b) mass
(c) viscosity
(d) specific gravity
Ans: d

82. The following indicate that battery on charge has attained full charge
(a) colour of electrode
(b) gassing
(c) specific gravity
(d)     all above
Ans: d

83. Dry cell is modification of
(a) Deniell cell      
(b) Leclanche cell
(e) Lead-acid cell  
(d) Edison cell
Ans: b

84. Capacity of a battery.is expressed in
(a) Ah
(b) Vh
(c) Wh
(d) kWh
Ans: a

85. In alkaline cell the electrolyte is
(a) dilute sulphuric acid
(b) concentrated sulphuric acid
(c) NaOH
(d)     KOH
Ans: d

86. Self charge of a Ni-Fe cell is _____ Edison cell.
(a)     equal to
(b)     less than
(c) more than
(d) much more than
Ans: b

87. Ampere hour capacity of an industrial battery is based on ____ hours discharge rate.
(a) 8
(b) 12
(c) 16
(d) 24
Ans: a

88. The body of Edison cell is made of
(a) bakelite
(b) rubber
(c) nickel plated steel
(d) aluminium
Ans: c

89. Specific gravity of electrolyte in Edison cell is
(a) 0.8
(b) 0.95
(c) 1.1
(d) 1.21
Ans: d

90. All the electrical connections between the battery and vehicle should be by
(a) thin aluminium wires
(b) thin copper wires
(c) rigid cables      
(d) flexible cables
Ans: d

91. A battery of 6 cells will show a drop of _____ volts from fully charged state to fully discharged state.
(a) 1.0
(b) 1.5
(c) 2.4
(d) 2.9
Ans: c

92. During the idle period of the battery, strong electrolyte tends to change the active material of the cell into
(a) Pb02
(6) PbSC-4
(c) PbO
(d) Pb
Ans: b

93. Chargmg of sulphated battery produces ____ heat.
(a) no
(b) very little
(c) less
(d) more
Ans: d

94. Hydrogen evolved during charging produces explosive mixture when it is more than
(a) 2%
(b) 4%
(c) 6%
(d) 8%
Ans: d

95. Weston standard cell at 20°C has voltage of ____ volts.
(a) 0.8
(b) 0.9
(c) 1.0187
(d) 1.5
Ans: c

96. Extent of corrosion in the underground metal work depends upon
(a) amount of moisture
(b) type of metals
(c) type of soil chemicals
(d) all above factors
Ans: d

97. Mercury cell has which of the following characteristics ?
(a) Flat discharge current-voltage curve
(6) High power to weight ratio
(c) Comparatively longer shelf life under adverse conditions of high temperature and humidity
(d) All of the above
Ans: d

98. Charging a sulphated battery at high rate results in
(a)     boiling of electrolyte due to gassing
(b)     warping of plates
(c) damage to separators, cell caps covers and battery case due to ex¬cessive temperature
(d) all above
Ans: d

99. Short circuiting of a cell may be caused
(a)   buckling of plates
(b) faulty separators
(c) lead particles forming circuit between positive and negative plates
(d) excessive accumulation of sediment
(e) any one of above
Ans: e

100. In a battery cover is placed over the element and sealed to the top of the battery container. This is done
(a)     to reduce evaporation of water from electrolyte
(b)     to exclude dirt and foreign matter from the electrolyte
(c) to discharge both of the above functions
(d) to discharge none of the above functions
Ans: c

101. For a cell to work, which of the following condition(s) become necessary ?
(a)     Two electrodes of different meta's should be inserted in the electrolyte, not touching each other
(b)     Electrolyte must chemically react with one of the electrodes
(c) Electrolyte liquid or paste should be conducting
(d) All above three conditions are necessary
Ans: d

102. Which of the following primary cells has the lowest voltage ?
(a) Lithium
(b) Zinc-chloride
(c) Mercury
(d) Carbon-zinc
Ans: c

103. Which of the following primary cells has the highest voltage ?
(a) Manganese-alkaline
(6) Carbon-zinc
(c) Lithium
(d) Mercury
Ans: c

104. While preparing electrolyte for a lead-acid battery
(a) water is poured into acid
(b) acid is poured into water
(c) anyone of the two can be added to other chemical
Ans: b

105. Which of the following battery is used for air-craft ?
(a)     Lead-acid battery
(b)     Nickel-iron battery
(c) Dry cell battery
(d) Silver oxide battery
 Ans: b

106. Which of the following cell has a. reversible chemical reaction ?
(a) Lead-acid
(b) Mercury oxide
(c) Carbon-zinc    
(d) Silver-oxide
Ans: a

107. Which of the following is incorrect ?
(a) A  storage cell has a reversible chemical reaction
(b) A lead-acid cell can be recharged
(c) A carbon-zinc cell has unlimited shelf life
(d) A primary cell has an irreversible chemical reaction
Ans: c

108. Which of the following has lower sp. gravity V
(a)     Dilute H2S04
(6)     Concentrated H2SO4
(c)  Water
(d)  Any of the above
Ans: c

109. Under normal charging rate, the charging current should be
(a) 10% of capacity
(b) 20% of capacity
(c)     30% of capacity
(d)    40% of capacity
Ans: a

110. When two batteries are connected in parallel, it should be ensured that
(a) they have same e.m.f.
(b) they have same make
(c) they have same ampere-hour capa-city
(d) they have identical internal resistance
Ans: a

111. A typical output of a solar cell is
(a) 0.1V
(b) 0.26 V
(c) 1.1 V
(d) 2 V
Ans: b

112. Petroleum jelly is applied to the electrical connections to the lead-acid battery
(a) prevent local heating
(b) prevent short-circuiting
(c) reduce path resistance
(d) prevent corrosion
Ans: d

113. When the load resistance equals the generator resistance which of the following will be maximum ?
(a) Current
(b) Efficiency of the circuit
(c) Power in the load resistance
(d) Voltage across the load resistance
Ans: c

114. The common impurity in the electrolyte of lead-acid battery is
(a) chlorine
(b) dust particles
(c) lead crystals    
(d) iron
Ans: d

115. In a lead-acid battery the energy is stored in the form of
(a)     charged ions    
(b)     chemical energy
(c) electrostatic energy
(d) electromagnetic energy
Ans: b

116. Which among the following constitutes the major load for an automobile battery ?
(a) Brake light    
(b) Self starter
(c) Parking lights
(d) Spark plugs
Ans: b

117. Which of the following factors adversely affects the capacity of the leadacid battery ?
(a) Temperature of surroundings
(b) Specific gravity of electrolyte
(c) Rate of discharge
(d) All of the above
Ans: d

118. Cells are connected in parallel to
(a) increase the efficiency
(b) increase the current capacity
(c) increase the voltage output
(d) increase the internal resistance
Ans: b

119. A constant-voltage generator has
(a) minimum efficiency
(b) minimum current capacity
(c) low internal resistance
(d) high internal resistance
Ans: c

120. Satellite power requirement is provided through
(a)     solar cells
(b)     dry cells
(c) nickel-cadmium cells
(d) lead-acid batteries
Ans: a