Power Generator

121. The flux in the core o a single phase transformer is

1. purely alternating one
2. purely rotating one
3. partly alternating and partly rotating
4. constant

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122. The frequency of the system with which several alternators are parallel can be increased by simultaneously ___________ of all generators

1. increasing the field excitation
2. decreasing the field excitation
3. increasing the speed of prime movers
4. decreasing the speed of prime movers

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123. The frequency og emf generated in an 8 pole alternator at 900 rpm is

1. 50hz
2. 120hz
3. 60hz
4. 240hz

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124. The friction and wind age losses in a dc motor depends upon

1. speed
2. armature current
3. flux
4. field and armature resistance

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125. The greatest eddy current loss occurs in the ___________ of a dc machine

1. field poles
2. commutating process
3. yoke
4. armature

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126. The greatest percentage of power loss in a dc motor is due to

1. wind age loss
2. core loss
3. copper loss
4. friction loss

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127. The greatest percentage of the heat loss in a dc machine is due to

1. eddy current loss
2. copper loss
3. hysteresis loss
4. frictional loss

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128. The iron losses in a dc motor depend upon

1. flux only
2. both flux and speed
3. speed only
4. temperature

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129. The main drawback of a dc shunt generator is that

1. terminal voltage drops considerably with load
2. shunt field circuit has high resistance
3. generated voltage is small
4. it is expensive

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130. The maximum flux produced in the core of a transformer is

1. directly proportional to supply frequency
2. inversely proportional to supply frequency
3. inversely proportional to primary voltage
4. inversely proportional to secondary voltage

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