单选题The frequency output of an operating alternator is controlled by the （）.Arelative speed of the rotor polesBnumber of turns of wire in the armature coilCstrength of the magnets usedDoutput voltage
单选题
The frequency output of an operating alternator is controlled by the （）.
A
relative speed of the rotor poles
B
number of turns of wire in the armature coil
C
strength of the magnets used
D
output voltage
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