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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1.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

2.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

3.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

4.單項(xiàng)選擇題Which of the listed items will stop a motor due to a reduction in voltage and restart it when the voltage is restored to normal?（）

A.Low voltage protection circuit
B.Non-renewable link fuse
C.Renewable link fuse
D.Low voltage release circuit

5.單項(xiàng)選擇題Which of the following statements concerning a simple parallel resistance circuit is correct?（）

A.The voltage drop across each resistor is the same
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 resistances
D.The total voltage equals the sum of the individual voltages across each resistance