问题
问答题 简答题
为什么交直流回路不能共用一根电缆？
答案
参考答案：
交直流回路是两个相互独立的系统，直流回路是绝缘系统，而交流回路是接地系统，若共用一根电缆，两者问容易发生短路，发生相互干扰，降低直流回路的绝缘电阻，所以不能共用。
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为什么交直流回路不能共用一根电缆？
参考答案：
交直流回路是两个相互独立的系统，直流回路是绝缘系统，而交流回路是接地系统，若共用一根电缆，两者问容易发生短路，发生相互干扰，降低直流回路的绝缘电阻，所以不能共用。
| 阅读理解。 |
| Everybody loves oranges. They are sweet and juicy. Some oranges do not have any seeds (种子). Some have a thick skin (厚皮) and some have a thin skin. The orange tree is beautiful. It has a lot of shiny (有光泽的) green leaves. The small white flowers smell very sweet. An orange tree has flowers and fruit at the same time. Farmers (农民) in other parts of Asia and the Middle East (中东) learned to raise (种植) oranges from the Chinese. Then they taught (教) Europeans (欧洲人). Orange is both a fruit and a color. The color of oranges is so beautiful that in English we use the name of the fruit for the color. |
| 1. Oranges are ______. |
[ ] |
| A. shiny and green B. old and wild C. sweet and juicy D. thin and white |
| 2. Some oranges do not have ______. |
[ ] |
| A. seeds B. sections C. flowers D. a skin |
| 3. Orange leaves are ______. |
[ ] |
| A. shiny B. thick C. sweet D. wild |
| 4. There are many ______ orange trees in China today. |
[ ] |
| A. shiny B. thin C. wild D. thick |
| 5. Europeans learned to plant orange trees from farmers in ______. |
[ ] |
| A. the Middle East and Asia B. Florida C. China D. Spain |