其他其他其他2007年第2期海船船员适任证书全国统考试题(总第43期)

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• 41The 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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• 42While paralleling two AC generators using synchronizing(同步的) lamps only, both lamps will go dark when the generators are ______.

  A.running at the same speed

  B.grounded

  C.of the same polarity(极性)

  D.in phase

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• 43The load sharing characteristics of two diesel generators operating in parallel are mostly dependent on their governor ______.

  A.load limit settings

  B.idle speed settings

  C.speed limit settings

  D.speed droop settings

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• 44Electric insulation is made of organic substances and so gradually ______with age.

  A.deteriorates

  B.increases

  C.are fouled

  D.becomes better

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• 45The main generators are connected to ______.

  A.distribution boards

  B.section boards

  C.emergency switch boards

  D.main switch boards

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• 46The operation of _____ two alternators requires the voltages to be equal and also in phase.

  A.control

  B.series-mounting

  C.running

  D.paralleling

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• 47______is a machine by which electrical energy is transformed into mechanical energy.

  A.An alternator

  B.An electric motor

  C.A diesel engine

  D.A main switchboard

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• 48A ground in an electrical circuit outside the engine room ______.

  A.cannot be detected under normal conditions

  B.is of no consequence to engineering personnel

  C.is indicated at the branch circuit breaker panel

  D.is indicated by the ground detecting lamps on the main switchboard

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• 49Time delayed or delayed action-type fuses are designed to ______.

  A.prevent grounds in branch circuits

  B.prevent opens in motor circuits

  C.permit momentary overloads without melting

  D.guard lighting and electronic circuits

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• 50When 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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