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The frequency of an alternator at a given RPM is determined by the ______.
A.number of turns of wire in the armature(电枢) coil
B.number of magnetic poles
C.strength of the magnets used
D.output voltage
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单选题The frequency of an alternator at a given RPM is determined by the （）.A
number of turns of wire in the armature coilB
number of magnetic polesC
strength of the magnets usedD
output voltage
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the temperature and flow quantity of the exhaust gas from M/EB
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amount of field excitation of the leading machineB
load-speed characteristics of the governorsC
amount of field excitation to the lagging machineD
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