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單項選擇題

When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is （）

A.lagging
B.leading
C.maximum
D.minimum

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單項選擇題

While paralleling two AC generators using synchronizing lamps only, both lamps will go dark when the generators are （）.

A.running at the same speed
B.grounded
C.of the same polarity
D.in phase

單項選擇題

Electric circuits are protected against overloads and short circuits by means of a/an （）.

A.circuit breaker
B.amplifier
C.diode
D.capacitor

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