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【单选题】

电磁铁的铁芯因该选用()

A.
永久磁铁
B.
永磁材料
C.
硬磁材料
D.
软磁材料
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题目标签:铁芯磁铁电磁铁
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参考解析:
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【单选题】Questions 57 to 61 are based on the following passage. Within fifteen years Britain and other nations should be well on with the building of huge industrial architectures for the recycling of waste. T...

A.
attempts to find efficient ways of recycling wastes
B.
efforts to protect the environment in British cities
C.
a good way to locate plants for waste recycling
D.
a cheap way to get energy from waste materials

【单选题】交流电磁铁动作过于频繁,将使线圈过热烧毁的原因是( )。

A.
消耗动能过大
B.
自感电动势变化过大
C.
穿过线圈中的磁通变化太大
D.
衔铁吸合前后总磁阻相差很大

【单选题】换向阀中的电磁铁发出噪音是()造成的。

A.
滑阀拉毛
B.
绕组绝缘不良
C.
衔铁接触不良
D.
电压太低