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單項(xiàng)選擇題

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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單項(xiàng)選擇題

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

單項(xiàng)選擇題

Current flowing in only one direction is called （）

A.alternating current
B.omnidirectional current
C.direct current
D.sinusoidal current

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