问题
选择题
| 求如图所示的交变电流的有效值，其中每个周期的后半周期的图象为半个周期的正弦曲线（ ） A．5A B．5 C．5 D．  |
A
/2
/2A
答案
答案：C
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| 求如图所示的交变电流的有效值，其中每个周期的后半周期的图象为半个周期的正弦曲线（ ） A．5A B．5 C．5 D． |
答案：C
Mr. and Mrs. White are teachers. They teach English in a big school. They go to 1 by car. They 2 home at eight o’clock in the morning and come back at four in the afternoon. They have two children. One is Tom. 3 is Ann. They are students. They are in 4 classes in the same school. They go to school on their bikes. It takes 10 minutes to get there. Some of their friends 5 to school too. After they get home, Tom and Ann do 6 homework. Mrs. White does the cooking for her family. Mr. White reads the newspaper. But 7 Mr. White helps his wife 8 their supper. After supper. 9 watch TV. The two children usually go to bed 10 from Sunday night to Thursday night, because the next day they must go to school.
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