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單項(xiàng)選擇題

Any electric motor can be constructed to be（）.

A.short proof
B.ground proof
C.explosion proof
D.overload proof

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單項(xiàng)選擇題

Current changing in direction and rising and falling in value is （）.

A.AC
B.DC
C.generator
D.fresh water generator

單項(xiàng)選擇題

The output voltage of a three-phase alternator is regulated by the （）.

A.AC voltage to the armature
B.AC voltage to the field
C.DC voltage to the armature
D.DC voltage to the field

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