问题
选择题
要改变直流电动机的转动速度，可采用的办法是 [ ]
A．改变电流的方向
B．改变磁感线的方向
C．同时改变电流方向和磁感线方向
D．只改变电流的大小
答案
答案：D
搜题请搜索小程序“爱下问搜题”
要改变直流电动机的转动速度，可采用的办法是 [ ]
A．改变电流的方向
B．改变磁感线的方向
C．同时改变电流方向和磁感线方向
D．只改变电流的大小
答案：D
| 阅读理解。 | |||||||||||||||
| |||||||||||||||
| 1. How old is Lucy? | |||||||||||||||
| A. 11. B. 12. C. 13. D. I don't know. | |||||||||||||||
| 2. What's Han Mei's favorite color? | |||||||||||||||
| A. White. B. Red. C. Black. D. Blond. | |||||||||||||||
| 3. Are they in the same school? | |||||||||||||||
| A. Yes, they are. B. No, they aren't. C. Yes, they do. D. No, they don't. | |||||||||||||||
| 4. Are they in the same class? | |||||||||||||||
| A. Yes. B. No. C. OK. D. I don't know. | |||||||||||||||
| 5. What color is Lucy's hair? | |||||||||||||||
A. White. |
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