(共42张PPT)
第十五章 电流和电路
第4节 电流的测量
人教版 九年级 物理 上册
小灯泡发光是因为有电流持续通过小灯泡。同一个小灯泡在不同的电路中，明暗不同，只是因为流过小灯泡的电流的强弱不同。
1. 知道电流的强弱；知道电流表的用途和符号；会正确使用电流表；能正确读出电流表的示数。
2. 通过连接电路测量电流，培养动手操作能力。
点击图片，认识电流的强弱
知识点 1
电流的强弱
电流：表示电流强弱的物理量；
符号：I
单位：
安培 简称：安 符号：A
常用单位：毫安（mA）、微安（μA）
单位换算：
1A=103mA 1mA=103μA 1A=106μA
安培，法国物理学家，在电磁作用方面的研究成就卓著，对数学和化学也有贡献。
了解常见的电流大小
刻度盘
数值单位
指针
调零螺母
正接线柱
负接线柱
量程为0～0.6 A
量程为0～3 A
电流表
A
+
－
符号
知识点 2
电流的测量
电流
测量工具
点击图片，练习电流表的读值
选择“0~0.6A”的量程时，则刻度盘上每个大格是_____A，分度值是_____A。
选择“0~3A”的量程时，则刻度盘上每个大格是_____A，分度值是______A.
0.2
0.1
1
0.02
练习电流表的读值：认识量程和分度值
明确所选电流表的量程；
确定电流表的分度值；
由指针位置读出示数。
0~0.6 A
0~3 A
0.02 A
0.1 A
量程
分度值
电流表的读数
电流表的连接
点击图片，学习电流表的连接
电流表的使用
电流表必须和被测的用电器串联。
电流必须从正接线柱流入，从负接线柱流出。
必须正确选择量程。
不允许把电流表直接连
到电源的两极！
找一找：下面四幅图的连接有问题吗？
不要把电流表直接连到电源的两极上．
电流表与被测用电器要串联；
电流要从电流表的“+”接线柱进，“-”接线柱出
不要超过电流表的量程；
例 以下电路中，电流表连接方法正确的是（ ）
A
A
A
A
B
A
A
C
D
例 根据所给电路图连接实物图。
L2
L1
L2
L1
A1
A2
A2
A1
1. 如图所示的电流表的读数为( )
A. 0.46 A B. 0.52 A C. 2.46 A D. 2.60 A
B
基础巩固题
2. 开关控制_________，电流表A1 测_________的电流，电流表A2 测_________的电流，再画出电路图。
干路
L1
干路
L2
L1
A2
A1
L2
L1
A2
A1
基础巩固题
3. 某同学在测通过灯泡的电流时,刚一“试触”就发现电流表的指针迅速摆动超过最大刻度,发生这种情况的原因可能是( )
A.电流表的“+”“-”接线柱接反了
B.灯泡的灯丝断了
C.电流表量程偏大
D.电流表量程偏小
D
基础巩固题
4. 连接实物图，要求两灯并联，开关控制两盏灯，电流表测灯L2的电流（约0.5 A），并画出电路图。
L2
L1
S
L2
L1
A
用电流表测量通过L2的电流,如图所示的是某同学的实物连接图,判断他的连线是否正确,有什么不妥。
① 开关闭合，电源两极直接用导线连接，形成电源短路;
② 电流表连接错了，测不出L2的电流；
③ 电流表“+”“-”接线柱接反，指针会反向偏转，将电流表损坏。
能力提升题
电流
定义：
表示电流强弱的物理量，用I表示
安培，简称安，用A表示
单位：
仪器：
连接方法
电流正入负出
串联在电路中
使用
A
不超量程
不能与电源直接相连
国际：
常用：
毫安（mA）和微安（μA ）
概念
测量
符号
电流表
作业
内容
教材作业
完成课后“动手动脑学物理”练习
自主安排
配套练习册练习
七彩课堂 伴你成长
To listen to 1c and 1d, then complete them.
To learn new words: pronounce, increase, speed, partner…
Objectives
Do you have difficulties in learning English
What things are difficult for you
Discussion
What’s your problem in learning English How do you solve them
I have difficulties in
learning English.
Can you help me
The difficulties he has in learning English.
New words: can’t pronounce some of the words
spell some English words
Speaking: be afraid to speak
Listening: can’t understand spoken English
Writing: can’t make complete sentences
Reading: read very slowly
Grammar: make mistakes
1a Learning English can be difficult. What things are
difficult for you Read the list. Check ( ) the
statements that are true for you.
____ I can’t pronounce some of the words.(v. 发音)
____ I can’t always understand spoken English.
____ I don’t know how to increase my reading speed.
____ I can’t spell some English words.
____ I often make mistakes in grammar.
(v. 增加；增长)
(n. 速度)
1b What other things are difficult for you
Make a list.
1. I don’t know enough words to write well.
2. ________________________________
3. ________________________________
4. ______________________________
5. ________________________________
can’t get the pronunciation right
be afraid people might laugh at me
forget a lot of new words
don’t get much writing practice
1c Paul finds it difficult to learn English. Listen and
complete the learning challenges he talks about.
1. He can’t get the__________________ right.
2. He___________ a lot of new words.
3. He can’t always_____________ when people talk to him.
4. He doesn’t get much___________ practice.
pronunciation
forgets
understand
writing
Challenges
1d Listen again. Complete the solutions.
1. ________________ can help.
He can always_____________________ in his notebook and study them at home.
He can_____________________________ to practice speaking.
He should find a _______ to practice writing.
Listening
write the new words
join an English language club
pen pal
Solutions
1e Role-play conversations using the information
in 1c and 1d.
① A: I don’t have a partner to practice English with.
B: Maybe you should join an English club.
② A: I always forget the new words.
B: You can write the new words in your notebook
and study them at home.
A: I can’t always understand when people talk to me.
B: Maybe you should join an English language club
to practice speaking.
A: I forget a lot of new words.
B: Maybe you should write the new words in your
notebook and study them at home.
Pair work
1.I often make mistakes in grammar.
mistake n. 错误；过失 make mistakes 犯错
Tom didn’t make a single spelling mistake in his composition.
汤姆在这篇作文里一个字也没拼错。
mistake vt. 弄错，误解
I mistook the number and went to the wrong room.
我记错号码, 走错了房间。
Language points
2. challenge n. 挑战
He wants a career that offers a challenge.
他想要一份有挑战性的事业。
vt. 向……挑战；对……提出异议
I challenged him to show his proof. 我要他拿出证据。
He challenged my view on that matter.
他就我对那件事的看法提出异议。
3. solution n. (问题、疑难等的) 解决；解答
It may take a long time to find a solution to the problem.
也许要花很长时间才能找到解决这个问题的办法。 The solution of the problem requires a lot of time.
解决这个问题需要很多时间。
4. Maybe you should join an English club.
join/join in/take part in
(1) join=be a member of 参加, 指加入某种组织，并成为其中的一员。
join the army / party 入伍/党 join the club 加入俱乐部
join in 后接活动名称
join sb. 加入到某个人群之中
Ⅰ. 用所给词的适当形式填空。
1. Sometimes, I can’t get the____________ (pronounce) right.
2. I don’t know how__________ (improve) my spoken English.
3. The more careful you are, the fewer_________ (mistake)
you’ll make.
4. You can find a pen pal to practice________ (write).
5. She can’t______ (spell) English words.
Exercises
pronunciation
to improve
mistakes
writing
spell
Ⅱ. 用方框中所给单词的适当形式填空。
We must learn to face the __________ in our life.
2. He has trouble in understanding _______ English.
3. Can you think of a good _______ to the problem
4. You can listen to the tapes to get much listening _______.
5. The more careful you are, the fewer _______ you’ll make.
solution, practice, mistake, spoken, challenges
challenges
spoken
solution
practice
mistakes
— Excuse me, can you teach me how to ______
this new word
— No problem. Look at my mouth and listen
carefully.
A. prove B. pronounce
C. prepare D. produce
B
中考链接
证明
准备
发音
生产
你能教给我这个新词怎么样……
— Miss Huang always advises us to practice
speaking English after class.
— She is right. Speaking is an important
language __________.
A. sign B. skill C. suggestion
符号
技能
建议
B
Review the new words and expressions you’ve learned today.
Preview the article How Can You Become a Successful Learner on page 6.
Homework
