如图1矩形导线框abcd固定在匀强磁场中,磁感线的方向与导线框所在平面垂直,规定

题型:选择题

问题:

如图1矩形导线框abcd固定在匀强磁场中,磁感线的方向与导线框所在平面垂直,规定磁场的正方向垂直纸面向里,磁感应强度B随时间t变化的规律如图2;若规定顺时针方向为感应电流i的正方向,线框中的感应电流下列四个选项中正确的是(  )

A.

B.

C.

D.

考点:法拉第电磁感应定律
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阅读理解。

     Many people have, to work on the weekend. Some people do not mind. Other people think it is terrible.

One man thinks that working on the weekend can be dangerous. He is John Brown. Mr. Brown works in

an office in New York.

     On Saturday, May 24, 1986, he went to the office to do some work. When he got in the elevator to go

home, it stopped between floors. Mr. Brown could not get out of the elevator. He was trapped (困住)! He

started to shout, but nobody heard him. Then Mr. Brown remembered that it was a holiday in America.

Nobody was going to come to work until Tuesday! There was nothing for Mr. Brown to do.

     He had to wait until one of his coworkers (同事) came to work and found him. With nothing to eat

or-drink, Mr. Brown ended up sleeping for most of the time.

     Early on Tuesday morning, the president of the company came into work and found the elevator was

not working. When the elevator was opened, Mr. Brown came out cold, weak, and tired. He had been in

the elevator for sixty-two hours!

     Now Mr. Brown says, "I only use elevators if they have telephones in them."

1. What does Mr. Brown think of working on the weekend?

A. It is happy.

B. He doesn't mind.

C. It can be dangerous.

D. He refuses to do it.

2. How long was he in the elevator?

A. From Saturday to Monday.

B. From Tuesday to Saturday.

C. More than three days.

D. More than two days.

3. Why did Mr. Brown spend so long in the elevator? Which of the following is NOT a reason?

A. It was a three-day holiday.

B. He had no food or drink.

C. The elevator stopped between two floors.

D. There was no telephone in the elevator.

4. How was Mr. Brown able to get out of the elevator?

A. The president discovered the elevator wasn't working.

B. The elevator started to work soon again.

C. His coworker who worked on the weekend helped him out.

D. His coworkers found him when they came back to work on Monday.

5. What is the best title (题目) for this story?

A. A Busy Weekend

B. An Interesting Elevator

C. Trapped in an Elevator

D. Elevator Safety

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A.User

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C.1万元~10万元

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