單項(xiàng)選擇題

In a three-phase circuit, the phase voltages are （）

A.120°apart
B.160°apart
C.180°apart
D.360°apart

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單項(xiàng)選擇題

The frequency of an alternator at a given RPM is determined by the （）.

A.number of turns of wire in the armature coil
B.number of magnetic poles
C.strength of the magnets used
D.output voltage

單項(xiàng)選擇題

The pushbutton on the handset of a ships sound-powered telephone must be depressed to （）.

A.talk then released to listen
B.listen then released to talk
C.both talk and listen
D.ring the station being called