问题 选择题
如图所示,两根相距为l的平行直导轨ab、cd、b、d间连有一固定电阻R,导轨电阻可忽略不计;MN为放在ab和cd上的一导体杆,与ab垂直,其电阻也为R;整个装置处于匀强磁场中,磁感应强度的大小为B,磁场方向垂直于导轨所在平面(指向图中纸面内);现对MN施力使它沿导轨方向以速度v(如图)做匀速运动;令U表示MN两端电压的大小,则(  )

A.U=vBl,流过固定电阻R的感应电流由b到d

B.U=vBl,流过固定电阻R的感应电流由d到b

C.U=vBl,流过固定电阻R的感应电流由b到d

D.U=vBl,流过固定电阻R的感应电流由d到b

答案

答案:A

阅读理解

Going green seems to be a fad(时尚)for a lot of people these days.Whether that is good or bad,we can’t really say,but for the two of us,going green is not a fad but a lifestyle.

On April 22,2011,we decided to go green every single day for an entire year.This meant doing 365 different green things,and it also meant challenging ourselves to go green beyond the easy things.Rather than recycle and reduce our energy,we had to think of 365 different green things to do and this was no easy task.

With the idea of going green every single day for a year,Our Green Year started.My wife and I decided to educate people about how they could go green in their lives and hoped we could show people all the green things that could be done to help the environment.We wanted to push the message that every little bit helps.

Over the course of Our Green Year,we completely changed our lifestyles.We now shop at organic(有机的)stores.We consume less meat,choosing green food.We have greatly reduced our buying we don’t need.We have given away half of what we owned through websites.Our home is kept clean by vinegar and lemon juice,with no chemical cleaners.We make our own butter,enjoying the smell of home­made fresh bread.In our home office anyone caught doing something ungreen might be punished.

Our minds have been changed by Our Green Year.We are grateful for the chance to have been able to go green and educate others.We believe that we do have the power to change things and help our planet.

小题1:What might be the best title for the passage?

A.Going Green

B.Protecting the Planet

C.Keeping Open­Minded

D.Celebrating Our Green Year小题2:It was difficult for the couple to live a green life for the whole year because________.

A.they were expected to follow the green fad

B.they didn’t know how to educate other people

C.they were unwilling to reduce their energy

D.they needed to perform unusual green tasks小题3:What did the couple do over the course of Our Green Year?

A.They tried to get out of their ungreen habits.

B.They ignored others’ ungreen behavior.

C.They chose better chemical cleaners.

D.They sold their home­made food.小题4:What can we infer from the last paragraph?

A.The government will give support to the green project.

B.The couple may continue their project in the future.

C.Some people disagree with the couple’s green ideas.

D.Our Green Year is becoming a national campaign.

单项选择题