问题
选择题
一个白炽灯泡上标“220V、40W”，那么为了使它正常发光，所使用的正弦交流电应是 [ ]
A．电压最大值为220V，电流最大值约为0.18A
B．电压最大值为311V，电流最大值约为0.26A
C．电压有效值为220V，电流有效值约为0.26A
D．电压有效值为311V，电流有效值约为0.18A
答案
答案：B
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一个白炽灯泡上标“220V、40W”，那么为了使它正常发光，所使用的正弦交流电应是 [ ]
A．电压最大值为220V，电流最大值约为0.18A
B．电压最大值为311V，电流最大值约为0.26A
C．电压有效值为220V，电流有效值约为0.26A
D．电压有效值为311V，电流有效值约为0.18A
答案：B
Today we 41 only three lessons in the morning. The first lesson is math. It 42 at eight o’clock and finishes at 43 to nine. It is in Room 101. But I don’t like math. Then the second lesson is my favorite 44 —music. It starts at nine o’clock. The 45 lesson in the morning is PE. It starts at ten 46 ten and finishes at five to eleven. We have our lunch at eleven thirty 47 the second floor of dining hall. We have two lessons 48 lunch. Art starts at two and at three o’clock we have a 49 lesson. We can learn a lot of knowledge about China. At about four in the afternoon 50 is over.
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