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单选题
A circuit breaker differs from a fuse in that a circuit breaker （）.
A
melts and must be replaced
B
is enclosed in a tube of insulating material with metal ferrules at each end
C
gives no visual indication of having opened the circuit
D
trips to break the circuit and may be reset
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考题
A circuit breaker and a fuse have a basic similarity(类似) in that they both ______.A.can be reset to energize the circuitB.should open the circuit when overloadedC.will burn out when an over current flow developsD.should short the circuit when overloaded
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单选题Running an electric winch at slow speed over a long period of time causes（）.A
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SDH circuit over a SONET network delivering it as a SONET signalC
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考题
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单选题Before any work on electrical or electronic equipment is performed, which of the following precautions should be carried out （）A
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Secure and tag the supply circuit breaker in the open positionD
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考题
单选题A circuit that has one wire in contact with the hull of the ship is a（）A
series circuitB
grounded circuitC
short circuitD
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考题
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prevent main circuit overloadB
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prevent alternator motorizationD
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考题
单选题A ground in an electrical circuit outside the engine room （）.A
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考题
单选题Which of the listed precautions should be taken when cleaning the internals of a motor with compressed air?（）A
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考题
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short-circuit protectionC
short duration surge protectionD
sustained overload protection
考题
单选题A circuit breaker and a fuse have a basic similarity in that they both （）.A
can be reset to energize the circuitB
should open the circuit when overloadedC
will burn out when an over current flow developsD
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考题
单选题You are attempting to parallel two AC generators, and the syncope pointer is revolving in the fast directionThis indicates that the frequency of the incoming machine is （）.A
higher than the bus frequencyB
lower than the bus frequencyC
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the same as the bus frequency and the circuit breaker may be closed at any pointer position
考题
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