问题 选择题

如图所示的电路中,电源电压保持不变,闭合开关S,当滑动变阻器滑片向左移动时

A.灯泡Ll亮度不变,L2变亮

B.电流表示数变小,电压表示数不变

C.电流表示数不变,电压表示数变大

D.电流表、电压表示数均不变

答案

答案:C

如图所示的电路中, 当滑动变阻器滑片所接的是电压表,滑片滑动时不改变电路中的电阻,电路中各处的电流不变,灯泡的亮度不变,只改变电压表所测电阻的阻值,当滑动变阻器滑片向左移动时,电压表所测电阻的阻值变大,电流不变,电压表的示数变大。

阅读理解

阅读理解。

                                                                  Never give up

      Since I was young, my mother has always spent lots of time sitting be-hind a sewing machine (缝纫机)

with a happy look on her face. For all the three kids in our family, she has made all the clothes.

      My mother makes it look so easy, but the first time I tried to make something, I just couldn't do it. I

worked too quickly, and when I finished, it looked bad. Soon, I just gave up.

      This summer, I really wanted to make a dress to wear at a party. I picked out some nice cloth, and I

found a nice style in a book. I got so excited about sewing that I couldn't even sleep.

       I started early the next morning. My mother was at a meeting, so if I had questions, there could be no

one to ask.

       I started sewing slowly and carefully, and I tried to do everything right. When I was sewing the top, I

made the neck too small. But the rest was fine.

      "I finally made it!" I shouted two hours later. And it fit! For the first time, I couldn't wear something I

had made with my own hands!

      If you want to learn something, my advice is: Don't give up when you can't do it well. Start with

something easy, and try your best.

1. How many children are there in the writer's family?

    __________________________________________________________

2. Why did the writer want to make a dress that summer?

    __________________________________________________________

3. Did her mother help her to make the dress?

    __________________________________________________________

4. What was the small problem about her dress?

    __________________________________________________________

5. What's the writer's advice? 

    __________________________________________________________

填空题