问题 问答题 简答题

什么是中性点位移?位移后将会出现什么后果?

答案

参考答案:

在大多数情况下,电源的线电压和相电压都可以认为是近似对称的,不对称的星形负载若无中线或中线上阻抗较大,则其中性点电位是与电源中性点电位有差别的,即电源的中性点和负载中性点之间出现电压,此种现象称为中性点的位移。出现中性点位移的后果是负载各相电压不一致,将影响设备的正常工作。

填空题
阅读理解

第三部分:阅读理解(共20小题,满分40分)

Many Chinese students who have learnt English for more than ten years are still unable to speak English very well when they meet a foreigner. They seem to have mastered the basic language structure, but a conversation in English will make them feel uneasy. They are afraid that other people might find out their mistakes.

It's unusual that many students who are bad speakers of English can write English perfectly. This proves that they are unable to organize their idea in English. The center of the problem is that they lack practice and confidence.

Why should you be afraid? Do you fear those foreigners with whom you are speaking? Don't be shy, they will not laugh at you just for a little mistake you make. The best way to get rid of trouble is to learn to speak by speaking more. I am sure that constant(经常的) practice will help you succeed.

56. What's the best title for the passage?

A. How to Speak to Foreigners          B. How to Study English Well

C. How to Organize the Idea in English   D. Practise Speaking English All the Time

57. Many Chinese students can write English very well, but they cannot speak English fluently because ________

A. they seldom meet foreigners    B. they seldom practise speaking English

C. they had no chance to speak English

D. they think it's enough to master the basic language structure only

58. So many Chinese students are afraid of speaking to foreigners because _____.

A. they are afraid they can't understand foreigners

B. they don't think their English is poor

C. they worry about making mistakes in their speaking

D. they didn't like speaking to foreigners

59. According to the passage, which of the following is NOT true?

A. We can speak English fluently by doing more speaking.

B. If you can write English perfectly, you are able to organize your idea in English.

C. If you can write good English composition, you can speak English very well.

D. Any Chinese students can't speak English fluently because they are afraid of making mistakes.

60. In the last paragraph, the expression "get rid of" means_______.

A. throw away     B. free oneself from     C. give up     D. do with