题干

发电机的转子在匀速转动过程中,下列物理量没有发生改变的有(  )

A:穿过线圈的磁通量

B:线圈中产生的感应电动势

C:闭合回路中的电流

D:闭合回路中电流变化的周期

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答案(点此获取答案解析)

D

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    The Fitting-in of Suzy Khan

    The first time I saw Suzy Khan, I knew I had to help her. She was really small for her age of 12. The boy in my class often1about her and laughed their heads off. She would open a book, pretending to read, with tears dropping on the open page.

    All I knew was that she was an orphan(孤儿) from Africa. She had just been adopted by a family in town who2that the best way for her to learn American ways of life was to be with American kids. I looked down at this 3girl and promised myself that somehow I would help her.

    But how could I help her4in with us? There had to be a5

    One day, when I went into the classroom, I saw that Suzy had6her geography book to a picture of a train, and in her notebook, she had made a(n)7copy.

    I was surprised and thought that she could do something in the coming 8show. So, I took her to see the art teacher, Miss Parker, and showed her what Suzy had 9"Why, it's wonderful," said Miss Parker, who then showed us a poster she had painted10the talent show. "I need more of these, but I just don't have enough11Could you help me, Suzy?"

    On the day of the talent show, Suzy's12were everywhere—all over the hall and all over the school, each one different.

    "And finally," said Mr. Brown, the schoolmaster, at the end of the show, "we have a(n)13award. I'm sure you've all noticed the wonderful posters." Everyone nodded. "One of our own students14them."

    I could hear everyone whispering. "Who in our school could draw15well?"

    Mr. Brown waited a while before saying, "16this student worked so hard on the posters, she deserves a17 too. Our mystery(神秘) artist is our new student—Suzy Khan!"

    Mr. Brown thanked her for all the wonderful posters and gave her a professional artist's set. "Thank you," she cried.

    I18 at that time when I was looking at her excited face, she'd probably never19anything in her whole life.

    Everyone started to20their hands. Suzy Khan gave them a shy smile and the applause was deafening. I knew then Suzy was going to be all right.