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(共42張PPT)
第十五章 電流和電路
第4節 電流的測量
人教版 九年級 物理 上冊
小燈泡發光是因為有電流持續通過小燈泡。同一個小燈泡在不同的電路中，明暗不同，只是因為流過小燈泡的電流的強弱不同。
1. 知道電流的強弱；知道電流表的用途和符號；會正確使用電流表；能正確讀出電流表的示數。
2. 通過連接電路測量電流，培養動手操作能力。
點擊圖片，認識電流的強弱
知識點 1
電流的強弱
電流：表示電流強弱的物理量；
符號：I
單位：
安培 簡稱：安 符號：A
常用單位：毫安（mA）、微安（μA）
單位換算：
1A=103mA 1mA=103μA 1A=106μA
安培，法國物理學家，在電磁作用方面的研究成就卓著，對數學和化學也有貢獻。
了解常見的電流大小
刻度盤
數值單位
指針
調零螺母
正接線柱
負接線柱
量程為0～0.6 A
量程為0～3 A
電流表
A
+
－
符號
知識點 2
電流的測量
電流
測量工具
點擊圖片，練習電流表的讀值
選擇“0~0.6A”的量程時，則刻度盤上每個大格是_____A，分度值是_____A。
選擇“0~3A”的量程時，則刻度盤上每個大格是_____A，分度值是______A.
0.2
0.1
1
0.02
練習電流表的讀值：認識量程和分度值
明確所選電流表的量程；
確定電流表的分度值；
由指針位置讀出示數。
0~0.6 A
0~3 A
0.02 A
0.1 A
量程
分度值
電流表的讀數
電流表的連接
點擊圖片，學習電流表的連接
電流表的使用
電流表必須和被測的用電器串聯。
電流必須從正接線柱流入，從負接線柱流出。
必須正確選擇量程。
不允許把電流表直接連
到電源的兩極！
找一找：下面四幅圖的連接有問題嗎？
不要把電流表直接連到電源的兩極上．
電流表與被測用電器要串聯；
電流要從電流表的“+”接線柱進，“-”接線柱出
不要超過電流表的量程；
例 以下電路中，電流表連接方法正確的是（ ）
A
A
A
A
B
A
A
C
D
例 根據所給電路圖連接實物圖。
L2
L1
L2
L1
A1
A2
A2
A1
1. 如圖所示的電流表的讀數為(　　)
A. 0.46 A　　B. 0.52 A C. 2.46 A D. 2.60 A
B
基礎鞏固題
2. 開關控制_________，電流表A1 測_________的電流，電流表A2 測_________的電流，再畫出電路圖。
干路
L1
干路
L2
L1
A2
A1
L2
L1
A2
A1
基礎鞏固題
3. 某同學在測通過燈泡的電流時,剛一“試觸”就發現電流表的指針迅速擺動超過最大刻度,發生這種情況的原因可能是(　　)
A.電流表的“+”“-”接線柱接反了
B.燈泡的燈絲斷了
C.電流表量程偏大
D.電流表量程偏小
D
基礎鞏固題
4. 連接實物圖，要求兩燈并聯，開關控制兩盞燈，電流表測燈L2的電流（約0.5 A），并畫出電路圖。
L2
L1
S
L2
L1
A
用電流表測量通過L2的電流,如圖所示的是某同學的實物連接圖,判斷他的連線是否正確,有什么不妥。
① 開關閉合，電源兩極直接用導線連接，形成電源短路;
② 電流表連接錯了，測不出L2的電流；
③ 電流表“+”“-”接線柱接反，指針會反向偏轉，將電流表損壞。
能力提升題
電流
定義：
表示電流強弱的物理量，用I表示
安培，簡稱安，用A表示
單位：
儀器：
連接方法
電流正入負出
串聯在電路中
使用
A
不超量程
不能與電源直接相連
國際：
常用：
毫安（mA）和微安（μA ）
概念
測量
符號
電流表
作業
內容
教材作業
完成課后“動手動腦學物理”練習
自主安排
配套練習冊練習
七彩課堂 伴你成長
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. 發音)
____ 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；增長)
(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. 錯誤；過失 make mistakes 犯錯
Tom didn’t make a single spelling mistake in his composition.
湯姆在這篇作文里一個字也沒拼錯。
mistake vt. 弄錯，誤解
I mistook the number and went to the wrong room.
我記錯號碼, 走錯了房間。
Language points
2. challenge n. 挑戰
He wants a career that offers a challenge.
他想要一份有挑戰性的事業。
vt. 向……挑戰；對……提出異議
I challenged him to show his proof. 我要他拿出證據。
He challenged my view on that matter.
他就我對那件事的看法提出異議。
3. solution n. (問題、疑難等的) 解決；解答
It may take a long time to find a solution to the problem.
也許要花很長時間才能找到解決這個問題的辦法。 The solution of the problem requires a lot of time.
解決這個問題需要很多時間。
4. Maybe you should join an English club.
join/join in/take part in
(1) join=be a member of 參加, 指加入某種組織，并成為其中的一員。
join the army / party 入伍/黨 join the club 加入俱樂部
join in 后接活動名稱
join sb. 加入到某個人群之中
Ⅰ. 用所給詞的適當形式填空。
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. 用方框中所給單詞的適當形式填空。
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
中考鏈接
證明
準備
發音
生產
你能教給我這個新詞怎么樣……
— 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
符號
技能
建議
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

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