问题 填空题

如图是大型电子地磅秤的电路图(电压恒定),当称物体的物重时,滑动变阻器R的滑片P会向B端滑动。变阻器连入电路的电阻    ,电流表的示数    (均选填“变大”、“变小”或“不变”)。这样只要把各电流对应的重量刻在电流表的刻度盘上,就可以显示被称物体的重量。当物重为Gl时,电流表的示数为Il。当物重为G2时,电流表的示数为I2。若Il<I2,则Gl   G2。(“<”、“>”或“=”)

答案

变小; 变大;  <

题目分析:观察图1—2可见:当称物体的物重时,滑动变阻器R的滑片P会向B端滑动,接入电路的电阻丝长度变小,导体的电阻与其长度成正比,变阻器接入电路的电阻变小,电路中的总电阻(R+R′)变小,电压恒定,由欧姆定律可知,电路中的电流变大,即电流表的示数变大,因为物体越重,滑片下滑的越多,接入电路的电阻丝长度越短,电阻越小,电路中电流越大,所以电流表的示数越小物重越小,若Il<I2,则Gl<G2

阅读理解

阅读理解

     In this age of Internet chat,   videogames and reality television,   there is no shortage of mindless

activities to keep a child occupied. Yet,   despite the competition,   my 8yearold daughter Rebecca

wants to spend her leisure time writing short stories. She wants to enter one of her stories into a writing

contest,   a competition she won last year.

     As a writer I know about winning contests,   and about losing them. I know what it is like to work

hard on a story only to receive a rejection slip from the publisher. I also know the pressure of trying to

live up to a reputation created by previous victories. What if she doesn't win the contest again? That's

the strange thing about being a parent. So many of our own past scars and dashed hopes can surface.

     A revelation (启示) came last week when I asked her,   "Don't you want to win again?" "No,  " she

replied,   "I just want to tell the story of an angel going to first grade."

     I had just spent weeks correcting her stories as she spontaneously (自发地) told them. Telling

myself that I was merely an experienced writer guiding the young writer across the hall,   I offered

suggestions for characters,   conflicts and endings for her tales. The story about a fearful angel starting

first grade was quickly "guided" by me into the tale of a little girl with a wild imagination taking her first

music lesson. I had turned her contest into my contest without even realizing it.

     Staying back and giving kids space to grow is not as easy as it looks. Because I know very little

about farm animals who use tools or angels who go to first grade,   I had to accept the fact that I was

coopting(借用) my daughter's experience.

     While stepping back was difficult for me,   it was certainly a good first step that I will quickly follow

with more steps,   putting myself far enough away to give her room but close enough to help if asked.

All the while I will be reminding myself that children need room to experiment,   grow and find their

own voices.

1. What do we learn from the first paragraph?

A. A lot of entertainments compete for children's time nowadays.

B. Rebecca is much too occupied to enjoy her leisure time.

C. Children do find lots of fun in many mindless activities.

D. Rebecca draws on a lot of online materials for her writing.

2. What did the author say about her own writing experience?

A. She did not quite live up to her reputation as a writer.

B. Her way to success was full of pains and frustrations.

C. She was constantly under pressure of writing more.

D. Most of her stories had been rejected by publishers.

3. The author took great pains to correct her daughter's stories because ______.

A. she wanted to help Rebecca realize her dreams of becoming a writer

B. she was afraid Rebecca's imagination might run wild while writing

C. she did not want to disappoint Rebecca who needed her help so much

D. she believed she had the knowledge and experience to offer guidance

4. What's the author's advice for parents?

A. Children should not be given every chance to voice their opinions.

B. Parents should keep an eye on the activities their kids engage in.

C. Children should be allowed freedom to grow through experience.

D. A writing career,   though attractive,   is not for every child to pursue.

判断题