问题 问答题 案例分析题

分析电弧产生的原理

答案

参考答案:

当触头在分断电路时,如果触头之间的电压达12—20V、电流达0.25—1A,触头间隙内就会产生电弧。电弧实际上是触头间气体在强电场作用下产生的放电现象。所谓气体放电,就是触头间隙中的气体被游离产生大量的电子和离子,在强电场作用下,大量的带电粒子作定向移动,于是绝缘的气体就变成了导体,电流通过这个游离区所消耗的电能转换为热能和光能,发出光和热效应,产生高温并发出强光,使触头烧蚀,并使电路的切断时间延长,甚至不能断开,造成严重事故。

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请阅读相关信息(选自Teens 1-3期的文章片段),并找出与之匹配的标题。如选E请涂AB,如选F请涂CD。

小题1:The question is, how faithful is it to the novel? “Any adaptation of such a classic will meet with criticism. Li’s brave attempt offers a new view of the novel and so encourages us to return to it to experience it again.” Hu Xiaowen, 16, of Shanghai No 3 High School.

小题2: In the words of the Chinese saying, it is of greater benefit to travel ten thousand miles than read ten thousand books. The Arctic taught me about the real world and the importance of protecting our environment.” Zhang said.

小题3:What do dreams mean? Dreams are not always filled with meaning. Sometimes dreams are just your mind playing with thoughts and images from your life, or things you may have read or seen on TV. But at other times, dreams show things that you want to achieve in real life, or things that cause you trouble or stress.

小题4: Being pure can be simple, not having complicated thoughts and being inexperienced. However, it doesn’t mean an ignorant or naive person. So, a person is pure in his or her nature if he or she is always enthusiastic and able to deal with difficult matters independently. This purity doesn’t pass with time.” 16-year-old Tan Mengxi of Nanjing said.

小题5: Because just thinking a word and not saying it produces the same brain waves, Greger and his team believe that soon they will be able to have a translation machine and voice box that repeats the word a person is thinking.

A.What Makes a Pure Girl?

B.A Chance in a Lifetime.

C.How do Dreams Work.

D.An Intern’s Dream.E. A Dream We can Love?

F. Speech for the Speechless.