问题 探究题

欧姆坚持不懈的探索精神,激发了同学们的学习热情,忠民和勇胜为探究小明提出的问题,设计如图所示电路,并准备了充足的实验器材.

(1)为完成探究,应该改变电压,观察电流的变化.请写出两种(不同角度)改变定值电阻两端电压的方法。

(2)忠民按设计好的电路进行实验,收集数据如下表(R 为定值电阻):

请根据表中数据,写出实验结论                                                  .

(3)勇胜在连接电路时,误将电压表与滑动变阻器并联,在实验中收集数据如下表(电源电压已知且不变):

①按勇胜的实验也能得出正确结论,请写出得出正确结论的办法.        

②实验中操作失误,往往是新收获的契机.请写出本实验操作过程中,滑动变阻器的电功率,随着它连入电路中电阻值的变化是如何变化的?

答案

(1)方法1:改变串联电池组的个数(或“改变电源电压”)    

方法2:改变滑动变阻器的阻值大小(或“改变与定值电阻串联的电阻阻值”) 

(2)导体的电阻一定时,导体中的电流与导体两端的电压成正比   

(3)

问题①:用电源电压减去滑动变阻器两端电压,得出定值电阻两端电压. 

 求出每次的电流与定值电阻两端电压的比值,比较比值,得出结论。

问题②:滑动变阻器连入电路中的电阻值减小时,其电功率先增大后减小。

阅读理解

阅读理解。

     The Chinese New Year is the most important holiday for the Chinese people. For the Chinese, the New

Year comes with the first day of the First Moon between January 21 and February 19. People prepare for the

holiday for fifteen days.

     Finally, at midnight it is New Year's Day or the first day of the First Moon. Chun Jie. People close the

shops and the streets are empty. Everyone locks the doors and stays at home.

     It is an important time for the family. The younger people bow to the older people. The Chinese call this

Kou Tou or kowtow. This means "to touch the ground with the forehead". Then the young people wish the

older people a happy New Year. The older people give children gifts or money in red envelops. The family

then goes to sleep.

     In the morning people dress in their best clothes. Some people stay at home, others to out to play a New

Year call. They're very polite and don't use bad words. It's the most important day of the year.

1. The most important holiday for the Chinese is ______.

A. Mid-autumn

B. National Day

C. the Chinese New Year

D. Christmas Day

2. For the Chinese, New Year comes ______.

A. on the first day of a year

B. on the last day of a year

C. between January 21 and February 19

D. on January 24th

3. On New Year's Eve, people usually ______.

A. go to the shops

B. close the shops

C. stay at home

D. Both B and C

4. The younger people bow to the older people to ______.

A. say goodbye

B. show respect (尊敬)

C. ask for money

D. apologize (道歉)

5. Which of the following is NOT right according to the passage?

A. People prepare for the holiday for fifteen days.

B. The Chinese New Year is an important time for the family.

C. People dress is their best clothes on New Year's Day.

D. It's polite to use bad words on New Year's Day.

单项选择题