單項(xiàng)選擇題A switchboard for an AC electrical system requires the use of which of the following devices（）.

A.Frequency meter
B.Ohmmeter
C.Induction voltage regulator
D.Current transformer governor


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1.單項(xiàng)選擇題The part of the shipboard electrical system used to control the distribution of power to the branch circuits, is the （）.

A.bridge control panel
B.disconnect links
C.governor relay box
D.main switchboard

2.單項(xiàng)選擇題A semiconductor is a material with a （）.

A.conductivity higher than a normal conductor
B.conductivity higher than a normal insulator
C.high conductivity at low temperatures
D.low conductivity at high temperatures

3.單項(xiàng)選擇題The sub-multiple prefix “micro” means （）.

A.thousandth (10 to the-3rd power)
B.millionth (10 to the-6th power)
C.billionth (10 to the-9th power)
D.trillionth (10 to the-12th power)

4.單項(xiàng)選擇題A signal derived from a controlled function and returned to the initiating point is called a/an （）.

A.monitoring signal
B.inverse signal
C.reverse signal
D.feedback signal

5.單項(xiàng)選擇題The purpose of a main switchboard circuit breakers reverse-power trip is to （）.

A.prevent main circuit overload
B.protect the circuit breaker blowout coil
C.prevent alternator motorization
D.prevent low voltage tripout