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

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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

單項(xiàng)選擇題

Which of the following statements is true concerning simple parallel resistance circuits?（）

A.The total current flow equals the sum of the individual currents
B.The total current flow equals the reciprocal of the sum of the individual currents
C.The total resistance equals the sum of the individual resistance
D.The total voltage equals the sum of the individual voltages across each resistance