71. The man advantage of an auto transformer over a two transformer is that
a. no cooling is required
b. hysteresis losses are minimised
c. eddy current losses are minimised
d. one winding is used as a result there is substantial saving in material

72. Auto transformer is lead
a. when operator is not available
b. when copper losses are to reduced
c. when higher efficiency is desired
d. when the transformer ratio is small

73. If the break occurs in a 200 : 100 volt auto transformer in the winding which is common to high voltage as well as low voltage side. then the output voltage on the low voltage side will be
a. 200V
b. 100 V
c. Zero

74. In an auto transformer . effective saving on copper and copper losses will occur , when the transformation ratio is
a. more than 1
b. nearly equal to 1
c. less than 1
d. 0.707

75. An auto transformer as
a. only one winding
b. two windings of the same guage wire
c. two windings of different material
d. more than two windings

76. Which of the following condition should be fulfilled for the parallel operation of two transformers?
a. percentage impedance should be the same
b. polarities of both secondaries should be same
c. Voltage ratings should be the same
d. All of the above

77. If the transformer core is made of copper
a. copper losses will be less
b. eddy current losses will be more
c. hysteresis losses will be more
d. none of the above

78. If the ohmic resistance of windings of a transformer is zero then
a. there will be maximum magnetic leakage
b. copper loss will be zero
c. core loss will be more than copper loss
d. transformation ratio will be infinite

79. If the secondary of a 5 : 1 step down transformer is connected to the primary of a down ratio of transformation will be
a. 5 : 1
b. 10 : 1
c. 50 : 1
d. 2500 : 1

80. The efficiency of two identical transformers under load condition can be determined by
a. back to back test
b. open circuit test
c. short circuit test
d. any of the above