2021年欧姆定律_2.pdf

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1、1 欧姆定律欧姆定律第二节(一)教学目的1.掌握，能熟练地运用计算有关电压、电流和电阻的简单问题。2.培养学生解答电学问题的良好习惯。(二)教具书写有问题和例题的投影幻灯片。(三)教学过程1.复习提问：(使用投影幻灯片)表 1、表 2 是某同学研究电流跟电压、电阻关系时的两组实验数据。请在表格中空白部分填写出正确数值，并说明道理。表 1 U(伏)I(安)R=5 欧1.5 0.3 0.6 精品w o r d 学习资料 可编辑资料-精心整理-欢迎下载-第 1 页，共 11 页2 4.5 表 2 R(欧)I(安)U=1.5 伏5 0.3 10 0.1 答：表 1 填 3 伏和 0.9 安。根据：在电

2、阻一定的情况下，导体中的电流跟导体两端的电压成正比。表 2 填 0.15 安和 15 欧。根据：在电压不变的情况下，导体中的电流跟导体的电阻成反比。2.进行新课(1)由实验我们已知道了在电阻一定时，导体中的电流跟这段导体两端的电压成正比，在电压不变的情况下，导体中的电流跟导体的电阻成反比。把以上实验结果综合起来得出结论，即。板书：第二节1.内容：导体中的电流跟导体两端的电压成正比，跟导体的电阻成反比。精品w o r d 学习资料 可编辑资料-精心整理-欢迎下载-第 2 页，共 11 页文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V

3、9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W

4、2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V

5、9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W

6、2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V

7、9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W

8、2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V

9、9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H43 是德国物理学家欧姆在19 世纪初期(1827 年)经过大量实验得出的一条关于电路的重要定律。的公式：如果用 U 表示加在导体两端的电压，R 表示这段导体的电阻，I 表示这段导体中的电流，那么，可以写成如下公式：I=U/R。公式中 I、U、R 的单位分别是安、伏和欧。公式的物理意义：当导体的电阻 R 一定时，导体两端的电压增加几倍，通过这段导体的电流就增加几倍。这反映导体的电阻一定时，导体中的电流跟导体两端的电压成正比例关系(IU)。当电压一定时，导体的电阻增加到

10、原来的几倍，则导体中的电流就减小为原来的几分之一。反映了电压一定时，导体中的电流跟导体的电阻成反比例的关系(IU/R)。公式 I=U/R 完整地表达了的内容。板书：2.公式：I=U/R I-电流(安)U-电压(伏)R-电阻(欧)有关的几点说明：中的电流、电压和电阻这三个量是对同一段导体而言的。对于一段电路，只要知道I、U 和 R 三个物理量中的两个，就可以应用求出另一个。使用公式进行计算时，各物理量要用所要求的单位。(2)应用计算有关电流、电压和电阻的简单问题。例题 1：课本中的例题 1。(使用投影片)学生读题，根据题意教师板演，画好电路图(如课本中的图 8-2)。精品w o r d 学习资料

11、 可编辑资料-精心整理-欢迎下载-第 3 页，共 11 页文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO

12、5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z

13、2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO

14、5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z

15、2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO

16、5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z

17、2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H44 说明某导体两端所加电压的图示法。在图上标明已知量的符号、数值和未知量的符号。解题过程要求写好已知、求、解和答。解题过程写出根据公式，然后代入数值，要有单位，最后得出结果。板书：例题 1：已知：R=807 欧，U=220 伏。求：I。解：根据I=U/R=220伏/807 欧=0.27 安。答：通过这

18、盏电灯的电流约为0.27 安。例题 2：课本中例题 2。(使用投影片)板书：例题 2要求学生在笔记本上按例题1 的要求解答。由一位同学到黑板上进行板演。学生板演完毕，组织全体学生讨论、分析正误。教师小结。电路图及解题过程是否符合规范要求。答题叙述要完整。本题答：要使小灯泡正常发光，在它两端应加 2.8 伏的电压。解释 U=IR 的意义：导体两端的电压在数值上等于通过导体的电流跟导体电阻的乘积。不能认为电压跟电流成正比，跟电阻成反比。因为这样表述颠倒了因果关系也不符合物理事实。例题 3：课本中的例题 3。(使用投影片)精品w o r d 学习资料 可编辑资料-精心整理-欢迎下载-第 4 页，共

19、11 页文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9

20、 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2

21、C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9

22、 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2

23、C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9

24、 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2

25、C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H45 板书：例题 3解题方法同例题2。学生板演完毕，组织学生讨论、分析正误。教师小结。解释 R=U/I的物理意义：对同一段导体来说，由于导体的电流跟这段导体两端的电压成正比，所以i 的比值是一定的。对于不同的导体，其比值一般不同。U 和 I 的比值反映了导体电阻的大小。导体的电阻是导体本身的一种性质，它的大小决定于材料、长度和横截面积，还跟温度有关。不

26、能认为R=U/I表示导体的电阻跟导体两端的电压成正比，跟导体中的电流成反比。由于电阻是导体本身的一种性质，所以某导体两端的电压是零时，导体中的电流也等于零，而这个导体的电阻值是不变的。通过例题 3 的解答，介绍用伏安法测电阻的原理和方法。板书：(书写于例题 3 解后)用电压表和电流表测电阻的方法叫做伏安法。3.小结(1)简述的内容、公式及公式中各物理量的单位。什么叫伏安法测电阻？原理是什么？(2)讨论：通过课本中本节的想想议议，使学生知道：电流表的电阻很小(有的只有零点几欧)，因此实验中绝对不允许直接把电流表按到电源的两极上。否则，通过电流表的电流过大，有烧毁电流表的危险。电压表的电阻很大(约

27、几千欧)，把电压表直接连在电源的两极精品w o r d 学习资料 可编辑资料-精心整理-欢迎下载-第 5 页，共 11 页文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H

28、4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA

29、5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H

30、4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA

31、5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H

32、4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA

33、5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H46 上测电压时，由于通过电压表的电流很小，一般不会烧毁电压表。4.布置作业课本本节后的练习1、4。(四)说明：通过例题，要领会培养学生在审题基础上画好电路图，按规范化要求解题。第四节电阻的串联(一)教学目的1.通过实验和推导使学生理解串联

34、电路的等效电阻和计算公式。2.复习巩固串联电路电流和电压的特点。3.会利用串联电路特点的知识，解答和计算简单的电路问题。(二)教具学生实验：每组配备干电池三节，电流表、电压表、滑动变阻器和开关各一只，定值电阻(2 欧、4 欧、5 欧各一只)三个，导线若干。(三)教学过程1.引入新课(1)阅读本节课文前的问号中提出的问题，由此引出本节学习的内容。板书：第四节电阻的串联(2)问：什么叫串联电路？画出两个定值电阻串联的电路图。(同学回答略，板演电路图参见课本图8-7)(3)问：串联电路电流的特点是什么？举例说明。学生回答，教师小结，在板演电路图上标出I1、I2 和 I。精品w o r d 学习资料

35、可编辑资料-精心整理-欢迎下载-第 6 页，共 11 页文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5

36、H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2

37、X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5

38、H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2

39、X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5

40、H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2

41、X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H47 板书：串联电路中各处的电流相等。I1=I2=I。(4)问：串联电路的总电压(U)与分电压(U1、U2)的关系是什么？举例说明。学生回答，教师小结，在板演电路图上标出U1、U2 和 U。板书：2.串联电路两端的电压等于各部分电路两端电压之和。U=U1+U2。(5)几个已知阻值的电阻串联后，总电阻和各电

42、阻之间有什么关系？这是本节课学习的主要内容。2.进行新课(1)实验：测 R1 和 R2(R3)串联的总电阻。问：实验的方法和原理是什么？答：用伏安法测电阻。只要用电压表测出R1 和 R2 串联电阻两端的总电压放用电流表测出通过串联电阻的电流，就可以根据逄出R1 和 R2 串联后的总电阻。要求学生设计一个测两个定值电阻(R1=2 欧、R2=4 欧)串联总电阻的实验电路。如课本图8-5 所示。进行实验：按伏安法测电阻的要求进行实验。测出 R1(2 欧)和 R2(4 欧)串联后的总电阻R。将 R1 和 R3 串联，测出串联后的总电阻R。将实验结果填在课文中的结论处。讨论实验数据，得出：R=R1+R2

43、,R =R1+R3。实验表明：精品w o r d 学习资料 可编辑资料-精心整理-欢迎下载-第 7 页，共 11 页文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档

44、编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1

45、T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档

46、编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1

47、T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档

48、编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1

49、T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H4文档编码:CO9H4Z2X8V9 HA5V1T9C8P8 ZO5H7W2C6H48 串联电路的总电阻，等于各串联电阻之和。(2)理论推导串联电路总电阻计算公式。上述实验结论也可以利用和串联电路的特点，从理论上推导得出。结合 R1、R2 的串联电路图(课本图 8-6)讲解。板书：设：串联电阻的阻值为R1、R2，串联后的总电阻

50、为R。由于 U=U1+U2,因此 IR=I1R1+I2R2,因为串联电路中各处电流相等，I=I1=I2 所以 R=R1+R2。请学生叙述 R=R1+R2的物理意义。解答本节课文前问号中提出的问题。指出：把几个导体串联起来，相当于增加了导体的长度，所以总电阻比任何一个导体的电阻都大，总电阻也叫串联电路的等效电阻。板书：3.串联电路的总电阻，等于各串联电阻之和。R=R1+R2。口头练习：把 20 欧的电阻 R1 和 15 欧的电阻 R2 串联起来，串联后的总电阻 R 是多大？(答：35 欧)两只电阻串联后的总电阻是1 千欧，已知其中一只电阻阻值是700 欧，另一只电阻是多少欧？(答：300 欧。)