单项选择题
In an alternating current electrical system, a low system power factor is a direct sign of （）
A.wasted energy
B.efficient operation
C.a short in the exciter field windings
D.an excessive number of minor system grounds
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An alternator is being paralleled with one on the lineAt the INSTANT the circuit breaker is closed, the frequency of the incoming alternator will normally （）.
A.increase
B.not change
C.decrease
D.be exactly 60 hertz -
单项选择题
Current flowing in only one direction is called （）
A.alternating current
B.omnidirectional current
C.direct current
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Accidental grounds in a shipboard electrical system must be repaired as soon as possible as they will （）
A.result in immediate power outages
B.damage circuit breakers
C.appear on the ground detection system
D.damage insulation and may cause outages
