问题 选择题

如果闭合回路中的感应电动势很大,则(  )

A.穿过闭合回路的磁通量变化很快

B.穿过闭合回路的磁通量变化量很大

C.穿过闭合回路的磁通量很大

D.闭合回路的电阻很小

答案

A、穿过闭合回路的磁通量变化很快,磁通量变化率很大,根据法拉第电磁感应定律分析可知感应电动势很大,故A正确.

B、穿过闭合回路的磁通量变化量很大,磁通量变化率不一定很大,根据法拉第电磁感应定律得知,感应电动势不一定很大,故B错误.

C、磁通量变化率与穿过闭合回路的磁通量没有直接关系,穿过闭合回路的磁通量很大,磁通量变化率不一定很大,根据法拉第电磁感应定律得知,感应电动势不一定很大,故C错误.

D、感应电动势与闭合电路中电阻的大小无关,故D错误.

故选:A.

阅读理解

阅读理解。

Dear Harry Potter,

     Hi! I'm Kevin from India. I really feel lucky to write you a letter.

    Though I live far away from your world, I think we are a little alike, You are a great wizard (奇才). You

have done lots of magical things to be amazed at. Although I don't do magic. I do believe in it. Well, I'm also

a wizard at school. And I can often get As, but I am not a bookworm. I like to play jokes in class, which

sometimes make my teachers angry. I also have many friends. They often get me into and out of trouble.

No matter what has happened, we still get close together.

     Oh, I almost forget to tell you that our school is almost like yours, Hogwarts. It's a special one for

excellent students. We have modern classes and technology lessons. But when much is given, much is

expected, so I often stay up late just to finish my homework. It really makes me tired and bored.

     Luckily, I can read your stories in my free time. I feel like I know you. You have a mind of your own.

You are young, but you know how to take responsibility(责任) for your decisions. Also you think with a

clear head even in danger. What a great boy you are! How I wish I could meet you soon!

     May you have a nice time. 

                                                                                                                                Yours,

                                                                                                                                Kevin

1. Kevin and Harry are a little alike because _______.

A. they almost have the same experience

B. their worlds are full of magic

C. their schools are close to each other

D. they both like the same subjects

2. In the passage, "a bookworm" means a person _______.

A. who likes keeping worms

B. who is loved by teachers at school

C. who is nervous of reading books

D. who enjoys nothing but reading

3. From the passage we know that Kevin _______.

A. is a slow boy in class

B. is fed up with much homework

C. doesn't believe in magic

D. likes to keep quiet in class

4. Kevin writes to Harry to tell him many things EXCEPT _______.

A. his friends

B. his school life

C. his trouble

D. his family

5. Which of the following is NOT the reason (原因) that Kevin likes Harry?

A. Harry can do magical things.

B. Harry keeps a clear head in danger.

C. Harry likes reading stories.

D. Harry takes responsibility for what he has decided.

单项选择题