如图甲所示，一个电阻为R，面积为S的矩形导线框abcd，水平旋转在

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如图甲所示，一个电阻为R，面积为S的矩形导线框abcd，水平旋转在匀强磁场中，磁场的磁感应强度为B，方向与ad边垂直并与线框平面成45°角，o、o'分别是ab和cd边的中点。现将线框右半边obco'绕oo'逆时针90°到图乙所示位置。在这一过程中，导线中通过的电荷量是

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D. 0

答案

答案：A

填空题

When I was young, I was always frustrated ( 挫败的 ), and almost everything ended in failure. I hung out everywhere all day. Having seen me like that, my father 小题1: to cheer me up.

One day, he gave me a cup of water and asked me to taste it. I found it 小题2: . My father said he just put one small spoonful of salt in the cup. And then, he led 小题3: to a lake, where he threw a big handful of salt 小题4: the lake, scooped up a spoonful of water and let me taste it again. He asked, "Does it 小题5: taste salty?"' "Not at all," I said. My father said, "Now you may know the root (根源) of your 小题6: :You are just a cup of water, not a lake. Be a lake and you won't小题7:sad any more."

I came to understand my 小题8: motive (目的): I feel unlucky 小题9: my heart is as small as a cup of water without great ideals as a lake.

To be a lake 小题10: great ideals, your feeling of failures and frustrations will be melted ( 融化) like the salt thrown into the lake.

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单项选择题

宽带调频信号的载频分量的幅度（）

A、等于未调载波的幅度

B、高于未调载波的幅度

C、恒为0

D、低于未调载波的幅度

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