單項(xiàng)選擇題

Since fuse elements are made of zinc or any alloy of tin and lead, the melting point of the fuse element must be （）.

A.higher than that of copper
B.lower than that of copper
C.equal to that of copper
D.reached when the conductor it is protecting becomes "white hot"

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單項(xiàng)選擇題

The most common source of excitation for synchronous motors is a/an （）.

A.low voltage battery
B.motor attenuator set
C.DC exciter generator
D.AC supply

單項(xiàng)選擇題

Before reassembling any machinery, you should （）.

A.replace all bearings regardless of length of service
B.apply a heavy coat of oil to all mating surfaces
C.clean any corroded surfaces and file all burrs smooth
D.coat all parts with alemite grease