问题 选择题
如图所示,矩形线圈有N匝,长为a,宽为b,每匝线圈电阻为R,从磁感应强度为B的匀强磁场中以速度v匀速拉出来,那么,产生的感应电动势和流经线圈中的感应电流的大小应为(  )

A.E=Bav,

B.E=NBav,

C.E=Bav,

D.E=NBav,

答案

答案:D

单项选择题
单项选择题

Ban the Band

Every year, our school has a dance for all the students. It’s a little funny seeing friends in clean shoes and trousers or colorful (1) , instead of the usual school uniform.

Most of us think the dance is great (2) even the teachers enjoy being there. (3) , two weeks ago someone said that there would be no (4) band this year— only CDs. "I don’t (5) it!" Amy cried out during the lunch break.

"Someone said the school couldn’t (6) a band, and they think it’s too noisy anyway, "added Daniel.

"Well, I don’t think it’s (7) enough without a band!" declared Angela, "and I’m going to see what can be done. "

Angela was as good as her (8) . In the afternoon she went to see the school headmaster who agreed to give the (9) some more thought. And he suggested that one (10) for having a band was to increase the price of each ticket from MYM5 to MYM10. Angela had to (11) out whether the students would like to do that."I need all of you to help me, " she (12) to our group before school the next day. "Mr. Berry gave me a list of all the names, and suggested we ask each one their (13) about the band and the extra cost. " (14) the day we asked around as Angela suggested, and wrote down people’s feelings about the band and the cost. We were amazed how much (15) there was for the band and everyone agreed to pay the extra MYMS."I’m surprised, " smiled Mr. Berry, when we gave him the (16) . "I really thought that only a few people (17) their band and that the cost would be too high. OK. Angela, your next (18) is to find a good band and line them up for the dance. "Angela was all smiles and (19) the news to Amy and Daniel. "You’re (20) , " smiled Daniel to Angela as he thought how close they came to having a less than perfect dance.

9()

A.schedule 

B.situation 

C.view 

D.action