單項(xiàng)選擇題

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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單項(xiàng)選擇題

Voltage generated by most AC generators is fed from the machine to the bus by means of（）.

A.brushes on a commutator
B.brushes on slip rings
C.slip rings on a commutator
D.direct connections from the stator

單項(xiàng)選擇題

Electrical leads and insulation on a motor should be painted with（）.

A.heat-resisting acrylic
B.heat-resisting aluminum
C.insulating varnish
D.insulating white lead