高二上册物理教案（共4篇）
2.知道做功和热传递都可以改变物体的内能.
3.了解热量的概念，知道热量的单位是焦耳.
重点目标
1.内能、热量概念的建立.
2.改变物体内能的途径.难点目标内能、热量概念的建立.
导入示标凉爽的秋夜，仰望星空时，会突然发现一颗流星在夜色中划过，并留下一条美丽的弧线.流星是怎样形成的呢?
目标三导学做思一：物体的内能
问题1：组成物质的分子在不停地做热运动，分子应具有什么能?物体的分子之间有引力和斥力，且分子之间有间隔，分子应具有什么能?什么叫物体的内能?你能说出它的单位吗?机械能和内能有什么区别吗?
小结：物体内所有分子由于热运动而具有的动能，以及分子之间势能的总和叫做物体的内能.它的单位是焦耳，简称焦，符号为J.机械能是宏观的，能看得到的，内能是微观的，是看不到的.
问题2：把红墨水滴入装满水的烧杯里，过一段时间，整杯水变为红色，这种现象说明了什么?当红墨水分别滴入热水和冷水中时，发现热水变色比冷水快，这又说明了什么?
小结：温度高的物体分子运动剧烈，内能大.所以物体的内能与温度有关.
问题3：小明说：“炽热的铁水温度很高，具有内能;冰冷的冰块温度很低，不具有内能.”小刚说：“炽热的铁水温度高，内能大;冰冷的冰山温度低，内能小.”你认为他们的说法正确吗?说出理由.
小结：一切物体都具有内能.物体的内能还与质量有关.
问题3：处理例1和变式练习1
例1：【解析】物体内所有分子热运动的动能与分子势能的总和叫做物体的内能温度越高，物体内能越大温度相同的同种物质，分子个数越多，分子热运动的动能与分子势物体内能越大
问题1：如右图所示，在一个配有活塞的厚玻璃筒里放一小团硝化棉，把活塞迅速往下压，你能观察到什么现象(棉花燃烧)，该实验说明了什么?你再将一根铁丝反复弯折数十次，用手接触弯折处，有什么感觉，该实验又说明了什么?
小结：做功可以改变物体的内能.
问题2：做饭时，铁锅为什么能烫手?放在阳光下的被子，为什么能被晒得暖乎乎?
小结：热传递也可以改变物体的内能.
问题3：处理例2和变式练习2
例2：【解析】来回拉绳子，绳子与管壁之间克服摩擦做功，使管内的酒精内能增大，温度升高;当把塞子冲出时，管内的酒精蒸气对塞子做功，将内能转化成机械能.正确的答案为A选项.
答案：A
变式练习
让学生进一步理解改变内能的途径有做功和热传递两种方法，选项ABD是做功改变物体的内能，选项C是通过热传递的方式改变物体的内能.
答案：C
学做思三：热量
问题1：什么叫热量?它的单位是什么?它用什么字母表示?
小结：物体通过热传递方式所改变的内能称为热量，它的单位是J，它用字母Q表示.
问题2：在热传递现象中，高温物体和低温物体的温度、内能和热量如何变化?
人生天地之间，若白驹过隙，忽然而已，我们又将接触新的知识，学习新的技能，积累新的经验，做好计划，让自己成为更有竞争力的人吧。计划怎么写才能发挥它最大的作用呢？以下是小编整理的高二上册物理教学工作计划3篇，希望能够帮助到大家。
高二上册物理教学工作计划 篇1一、基本情况分析
理科班虽有部分学生基础稍好，但文科班学生没有养成良好的学习习惯，对物理会考的重视有待于提高。因此，我们在教学中一方面要充分了解他们，与他们多沟通，给他们以信心，提高他们学习物理兴趣；另一方面要抓住课堂这块主要阵地，讲究技巧和趣味性，切实提高学生的整体素质，为以后高考复习打下坚实的基础。
二、教学任务：
理科班完成选修3—1和选修3—2大部分，文科班完成选修1—1、1—2的教学任务。
三、教学目标
通过教学，学习必备的物理知识与技能，发展自主学习能力，养成良好的物理思维习惯，达到学生能力增强的目的。学生能独立完成教材上的习题，能在老师的指导下完成课外布置的习题，能做其他参考书上的部分练习，逐步培养学生热爱物理，达到提高学生的综合素质的目的。
四、教材分析
新物理课程标准改变了原有物理课程的模式，在高一学习了物理必修1和必修2两本教材，这两本主要在于基础的学习。现在到了高二了，对于理科选修的物理3系列，这个系列的强调的是要求学生更深入的了解这些知识以及在于对这些知识的应用。在物理选修3—1整本书中，主要研究的是电学与磁学，可以说是整个物理学中比较难的，它与必修模块中的内容紧密的联系的在一起。在选修3—2中，主要是对选修3—1进行了加深，将电学与磁*系在一起，形成了电磁学，其次对电流也进行了加深，还加上了现在比较热门的传感器。
五、教学策略
针对本年级的总体成绩，主要在于重点打好基础，具体措施如下：
1、精讲精练
a、精讲：首先，概念的引入和讲解务必要清楚。为此应该对重点的内容反复强调，对重点概念的引入和理解应用要多举例，结合情景进行教学，这是课改的要求，其次，把握好进度，切勿图快，尤其在难点的教学中，要把握好进度。
b、精练：本学期的习题肯定不少，如何以的效率获得的效果是值得探讨的课题，尤其体现在习题的练习和讲解中，作业和课堂练习题都打算在归类的基础是上分层，做到有纵有横。
2、及时的反馈
本学期要在课上和课后都有一个较完整的反馈机制，比如在上课及时进行反馈性的练习，作业有问题的学生要与之交流，从中了解问题所在，以便及时改进，对于学习有困难的学生要经常沟通。
3、继续深入全面的开展个性化教育。
高二上册物理教学工作计划 篇2一、指导思想：
以物理新课程标准为指引，紧跟学校教学工作计划，以提高课堂教学质量和培养学生综合能力为目标，抓好常规教学，夯实基础，不断优化课堂教学的方法和手段，以培养学生自主学习和合作学习的能力以及创新思维能力作为教学教研工作的中心任务。
二、现状分析
1、基本情况：
本人所授班级为高二6、7、8、9四个班，均为普通理科班，其中3班是我本学期才接手的班级，本班在高一时基础较好，但从本学期还需要一个熟悉和相互适应的过程，希望能尽早进入状态。本学期理科班周课时为6节。理
本学期，我将以学校教务处工作意见为指导，围绕物理教研组计划要求认真学习教育教学理论，认真研究和学习新课程标准，积极推进新课程改革的实施，转变教学方式和学生学习方式，为学生的终身发展奠定良好的基础，做好高二物理教学工作。在加强常规教学的同时，积极开展科研课题的实验和研究，以及为高三培养物理尖子作好培优工作。
2、学情分析：
理科班大多物理生有学习物理的兴趣，有较好的`学习习惯和一定的学习方法。但学生程度参差不齐，由于高一课时紧，内容多，部分学生必修1、2的知识遗忘较严重，理解掌握上差别较大。有极个别学生基础薄弱，没有养成良好的学习习惯。
三、教学任务与工作目标
1、这学期主要开设3—1，并尽量在一月份底进3—2的教学，并力争完成1—2章的教学任务。通过教学使学生初步认识基本的物理反应原理，并能运用原理解决一些简单的实际问题。
2、以分班选课为契机帮助学生确立将来的高考目标，积极建设良好的班风、学风。加强学习方法的指导，帮助学生掌握高效的学习方法，以应对日益加深的学习内容。
3、做好高中物理新课程标准的实施工作，在实践中不断探索和研究，增强对新课标的理解和驾驭能力；立足课堂开展教学研究，实现课堂教学的化。
4、根据学校工作计划，结合学科实际，落实各项教研和教学常规工作。树立质量为本的教学理念，全面推进教学改革，确保教学质量稳步提高。不断更新教育观念，积极投身教学改革，促进教学质量稳步提高。
四、具体工作措施
1、认真做好教学常规，确保教学有效开展
深入备好每节课，按照课程标准的要求，积极认真地做好课前的备课资料的搜集工作。然后，备课组共同研讨确定学案内容，根据班级具体情况适当调整、共享。部分章节内容制作成教学课件后，再根据班级具体情况适当调整、共享。此项工作上课前两至三天完成。认真上好每节课，积极实践新课程理念，把握好课堂，提高课堂教学的实效性。精心设置习题，合理、分层布置学生作业，书面作业要求全批全改；学生配套教辅《金版》不定期抽查，发现问题及时解决，及时反馈。精选每章的测验题，与备课组共同出题，并要达到一定的预期效果。对每一次测试要认真分析，总结，为学生确定合理的目标。
2、积极开展实验教学，提高学生学习兴趣
物理是一门以实验为基础的自然科学，积极、认真开展实验教学有助于提高学生的学习兴趣和直观理解，有助于培养学生实验能力。依据学校现有实验条件，在保证演示实验绝大部分完成的基础上，适当开展学生分组实验和课后实践。
3、做好综合实践，践行分层教学
（1）成立物理学习兴趣小组（奥赛小组），培养特长生学习、探究物理的兴趣和能力。
（2）利用晚自习做好缺差辅导，确保每一个学生学习不掉队，力争高中学业水平测试全面通过。
4、积极参加教研活动，提高教学业务能力
学习物理课程标准，明确新课程的具体要求，利用每周的教研组和备课组活动时间，认真学习新课程教学理念，深入研究教育教学方法。
高二上册物理教学工作计划 篇3进一步深化教育教学改革，树立全新的语文教育观，构建全新而科学的教学目标体系、物理网特制定高二上册物理选修3-1静电现象的应用教学计划模板。
教学内容 人教版物理选修3-1《静电现象的应用》
教学目标
1.知道静电感应产生的原因，理解什么是静电平衡状态。
2.知道静电平衡时，净电荷只分布在导体表面且导体内部场强处处为零的特点。
3.静电屏蔽及其应用
4.通过对静电平衡状态下导体内部场强处处为零的推导过程培养学生逻辑推理的能力。
借助实物与演示实验，分析静电平衡时导体上的电荷分布和内部场强的特点，从而得到静电保护的方法。
观察生活中的现象，体会生活、生产中的静电现象，培养探索乐趣。
教学重点
1.静电平衡状态下导体的特点。
2.静电屏蔽及其应用。
教学难点
应用静电平衡的知识，理解静电平衡的特征，认识导体的电荷分布特点。
教学方法 实验情境教学法
教学过程
(一)实验引入：借用原人教版高中物理第一册课本绪言中“笼外电闪雷鸣，笼内小鸟安然无恙”实验情境引入，设疑激趣。
(二)讲解新课：
(设问)1.电场的基本性质：电场对放入其中的电荷有什么的作用?
2.金属导体的重要特征(导电的原因)是什么?
(答)1.电场对放入其中的电荷有力的作用。
2.(课件展示说明)金属导体内部有大量的自由移动的电荷(电子)。
(设问)3.如果我们给上边的金属导体加上一个匀强电场，导体会有什么变化呢?
(用多媒体课件展示情境，即课本23页图1.7—1)
思考讨论：
1.导体两端的感应电荷会在空间产生电场吗?
2.产生电场的方向怎样?
3.现在空间中有几个电场存在?
4.感应电荷产生的电场与外电场叠加，使导体内部的电场怎样变化?
5.内部的电场被减弱了，但自由电子是不是仍然要受到电场力的作用，继续定向移动?
6.继续定向移动的结果是什么?
7.最终达到一种特殊的状态，内部的场强处处为零，定向移动停止。
得出结论：处于静电平衡状态的整个导体是个等势体，内部的场强处处为零。
8.把上边的实心导体挖空，变成一个导体壳，对静电平衡状态有影响吗?
9.如果把一个小的导体放入导体壳中，小导体还会发生静电感应现象吗?
设计意图：通过问题串组织教学，让学生认识逐步深化。
前后呼应：现在你该明白“笼外电闪雷鸣，笼内小鸟安然无恙”了吧?
(教师讲解)静电现象在现代生产、生活和科学技术中的应用：
1.有的电学仪器和电子设备的外面套有金属罩
2.中国科技馆高压放电区的保护
3.静电屏蔽衣
4.收音机、汽车的天线
(三)归纳小结：
1.静电感应：
感应电荷：
2.静电平衡状态：
处于静电平衡状态的导体的特征：
3.静电现象及其应用
(四)作业与拓展：
1.《同步解析与测评》相关题目。
2.中国科技馆高压放电区的保护与其它的保护有什么区别?
3.自拟题目撰写一篇以静电知识为题材的科技小论文。
1 This woman is one of the greatest scientists of all times. Even her name tells you that she likes science: a good scientist should want to find out answers and ask many questions --- in other words they should be curious. This woman was certainly curious. Together with her husband, she tried to learn the secrets of radioactivity. The couple were awarded the Nobel Prize for Physics in 1903. Eight years later, she received a second Nobel Prize, this time for chemistry.
2 It is said that this English gentleman was sitting in his garden one day when suddenly he was hit by a falling apple. The story is probably not true, but this man did mention that he got one of his best-known ideas while watching apples fall from a tree. His name makes you think that he was not too interested in old things. He discovered the force of gravity, and he drew up a system of how objects move. His laws for motion are still used in physics today, at least in schools and universities.
3 Food is what sets this great mind on fire. Rice, to be exact. This great mind has spent most of his life looking for ways to help farmers grow more rice so that all of us will have enough food to eat. He is known as the father of modem rice, but because of his long friendship with all the farmers in China, he would rather be known as 搕he farmer?
Listening Texts to Unit One (Workbook)
Part 1
Scientists often look at nature in order to find new ideas. In ancient times, Chinese scientists studied how spiders make silk. Modem scientists are interested in the spider, too. A spider can make silk that is much stronger than most man-made materials. A spider抯 silk doesn抰 break easily. Instead of breaking, it gets longer. Best of all, the spider produces the silk without the use of dangerous or poisonous chemicals. If we could learn to use the technique, we might be able to use the strong silk to make things like seat belts and wires that hold up bridges.
Part 2
There are many other examples of how new technology has been developed by learning from nature. A group of German scientists wanted to find out why leaves and flowers are able to stay so clean. They decided to take a closer look at the white lotus, a flower that is known for its clean leaves. At first, the scientists believed that a very flat leaf would be better at staying clean. However, when they looked closely at the white lotus, the scientists saw that the leaf was in fact covered with tiny hairs and needles. The needles and hairs collect the dust that falls on the leaf so that a raindrop can easily wash it off. The German scientists used this technique to design a new kind of paint. The new paint could keep houses looking clean for years.
Scientists also believe that the butterfly could teach us a way to keep our computers cool. A computer must be kept cool to function well. The fans we use today are not always good enough. The butterfly is cold-blooded and must change its body temperature all the time. Scientists have found that there are small parts on its wings that the butterfly uses to change its temperature. If scientists can learn how this is done, it may be possible to use the same method to keep computers from becoming too hot.
Listening Texts to Unit Two (Students?Book)
Part 1
R: Reporter K: Mr Keller
R: Good morning, Mr Keller. My name is Harry Hunter and I work for the Daily Times. I would like to ask you a few questions about Jim Gray.
K: Good morning, Mr Hunter. What would you like to know a1抩ut Mr Gray?
R: Well, I want to know if it is true that Mr Gray no longer works for your company.
K: Yes, that抯 true. Mr Gray was fired today. He has been having problems lately and it was time for him to leave.
I see. What kind of problems?
K: Mr Gray was too slow and it took him too long to do his job. He talked too much and was noisy and sometimes even wild. He was not serious enough. Instead of thinking about work, he would spend too much time disturbing the other workers with questions and comments.
R: So the other workers didn抰 like Mr Gray?
K: Mr Gray was very nosy, always trying to find out what other people were doing. Many people were also unhappy with Mr Gray because he was rude and said bad things about people.
R: I see. Were there any other reasons why you fired him?
K: Yes, Mr Gray was also careless with his money. Now if you will excuse me, I have to get back to work.
K: Thank you for answering my questions.
Part 2
P: Paul W: Wendy
P: Hi, Wendy. Did you hear that Jim was fired today?
W: Yes, I did. Isn抰 it awful! I have worked with him for ten years and he is one of my best friends. I can抰 believe that he was fired.
P: I don抰 understand it, either. Jim faced many difficulties but wouldn抰 give up. He was careful and always took the time to do a job well.
W: Even when he was very busy, Jim always found time to speak to others. He was funny and happy and liked to make others laugh. He always had a kind word for me.
P: Yes, he was always interested in other people and cared about their life and problems. When my wife was ill, he always asked me about her and tried to cheer me up.
W: Jim was always so generous. He was happy to spend money on good meals and gifts.
P: Yes, he was. And he was also very honest and always told people what he thought about something.
W: I suppose we won抰 see him very often in the future. I抣l miss him.
F? I抣l miss him, too.
LISTEN1NG TEXT to Unit Two(for workbook):
The chief editor of a daily newspaper is having a meeting with the journalists. She is telling them what she wants them to do today
Good morning, everybody. Listen carefully. This is what I want you to do.
Mick, Jane Scott, the sportswoman, is arriving at the airport this morning. Her plane arrives at 11. Will you be there please? I want you to get a good photograph of her. See if you can talk to her. Ask her what her future plans are, OK?
Bob, the medical conference opens today at the Capital Hotel. It starts at 9 o抍lock, so you抣l have to hurry. I want you to listen to the opening talk and make some notes. Get a photograph too of the person giving the talk.
Susan, I want you to interview someone at the Home Office. These new traffic plans are very interesting. I want you to set up an interview today. I want you to put your report in tomorrow抯 paper. Get as much information as you can. Try to collect some plans or diagrams. They will be very useful.
LISTENING TEXT to Unit Three (for Students?book):
S = Shop assistant A = Amy D = Danny
S: Can help you? What is it you are looking for? Furniture for the bedroom, the kitchen or the living room?
D: We抮e looking for a few things, but we aren抰 very sure yet. We bought a new flat, and we already have some furniture, but the new house is so big. We can use a few more things, and perhaps replace some very old pieces.
A: I think we need a kitchen table, one that is large enough to have dinner with five or six people.
S: Very well. If you would like something modern, I suggest you think of something like this. The legs of the table are silver coloured while the table top Is made of thick glass. Very 1抏autiful and very easy to clean.
D: Yes, I really like that.
A: No. I don抰 like such cold and hard things. I think a table made of wood would look much nicer. Wood is warm, and makes you feel comfortable.
D: Honey, I know you like that, but I抦 afraid it抣l be too expensive.
S: That抯 no problem. I can show you some really nice modern tables that look as if they were made of wood.
A: Great! We are also looking for something on the wall. There抯 a Hg piece of white wall over the sofa.
S: Were you thinking of a painting or perhaps a poster or something
D: Yes. Could you show us something?
S: Something classical?
A: Oh, no. You can show us something modern. I like classical things in the kitchen and the bed room, but our living room is quite modern, isn抰 it, Danny?
D: By the way, we are also still looking for two comfortable chairs, something modern and classic at the same time. Would you have anything like that?
S: Oh dear! Oh dear! What do you mean by that?
A: Well, something classic and fine but also cool, you know.
LISTENING TEXT to Unit Three (for Workbook):
The history of architecture in China and most European countries is very different. As a result, the way people look at art and architecture has also developed along different lines.
Much of China抯 ancient architecture was constructed of wood. Only the Great Wall and city walls were made of large bricks. Earthquakes have occurred quite often in China抯 history. Besides that, many temples were destroyed by fire. Sometimes the fires were caused by accident. However, it also happened that emperors would destroy temples and architecture that were built in the past. They wanted to get rid of all architecture that reminded people of the former emperor. After burning the old temples and palaces, the emperor would have everything built new in the style that he preferred. That抯 why all over China we find many temples that were rebuilt or restored about 250 to 300 years ago, during the age of Qianlong. Few temples are left over from earlier times.
Much of Europe抯 ancient architecture is 300 to 1,000 years old. Architects used natural materials, such as stone and brick to construct their buildings. There weren抰 many earthquakes, and unlike China, European kings would usually not burn the churches and other architecture built before their time. They constructed new buildings in the style they preferred at other places.
Wood is not a very strong material. Weather conditions make repairs necessary and by the end of about 100 years usually every part of a wooden construction has been replaced. So, although the design can be hundreds of years old, every part of the building may have been made less than a hundred years ago. Stone and brick are strong enough to stand the test of time. These materials do not need to be replaced. So when looking at old buildings in Europe, we are actually looking at what was built many centuries ago. While in China the architecture may be old, what we look at is in fact quite new.
LISTENING TEXT to Unit Four (for Students?book):
A Dialogue between a librarian and a student
S: Hello. Could you help me, please? I want to read some poems.
L: Have you read any poetry before?
S: Yes, we read some at school, but I didn抰 like it very much. I want to find something nice.
L: There are different ways to choose a poem. If you have a favourite writer, you can choose a book with his or her poems, but if you don抰 know any names, you抎 better start with books that are collections of poems. In such books you usually find poems by different writers. You see here抯 a book called A Garden of Poems, or this one, 1001 Songs and Poems in English.
S: Should I read all those poems?
L: No, don抰 worry. What most people do is to go through them until you see a poem that you like. Maybe you like the title, or the topic, or you might like the first or last lines of the poem.
S: I see. What else have you got?
L: Some books bring together the work of writers from a certain period of time. You see, English Poems of the Early Seventeenth Century or Poetry between the World Wars. Other books have poems about a certain topic. The topic can be human feelings, such as humour or love. There is also poetry about nature, you can look for poems about flowers, trees and plants or, about the sea or the countryside. So, what would you like to read?
S: I don抰 know. Shakespeare, maybe?
L: I think Shakespeare is a little bit difficult for you. It抣l be easier if you choose something modern. What kind of topic would you like?
S: I like reading about nature.
L: Have a look at this book. It抯 called The Earth is Painted Green. If you have any more questions. you can come and ask me.
S: Yes, I抣l do that. Thank you very much for your help.
LISTENING TEXT to Unit Four (for Workbook):
People invented poetry as a help to remember things. Before the invention of writing there was no other way to remember important things. People early discovered that rhyme and rhythm were very helpful when they were trying to remember things. So, they made poems to help them remember all the things they needed to know and sass on from generation to generation. For example. to remember their history they recited great stories about their ancestors and the wars that were fought. But people
also needed to remember practical things such as where to find good caves to sleep, where to find water that could be drunk or when to plant crops.
We no longer need poetry to remember things. But that doesn抰 mean that we shouldn抰 or couldn抰 use it to help us remember and learn things better. In fact, there are a number of quite famous short poems that can help us with things that are difficult to remember.
We can learn and remember important dates in history using rhyme. The most famous of these is: 慖n fourteen-ninety-two, Columbus sailed the ocean blue.?To remember that it was in 1492 that Columbus discovered the Americas. There are also short rhymes to remember how many days each month has.
30 days has September,
April, June, and November.
All the rest have 31. Fine!
February 28 except when 29.
We can even learn how to spell English words from a short poem. The word 搑eceive?sounds like 揵elieve? but the spelling is not the same. Listen to the following short poem. It is very useful to help students learn and remember how to spell some difficult words in English and it always works.
I before e except after c
or when sounding like a
as in neighbour and weigh.
LISTENING TEXT to Unit Five (for Students?book):
Good morning and welcome to the Language School at Dublin University. I抦 very happy to greet you all to our Summer Programme and hope that you will not only learn a lot more English, but also learn about the Irish way of life. Before you go to your classrooms, I want to have a quick look at your weekly timetable with you. Classes are taught from Monday to Friday with four classes in the morning and three classes in the afternoons. One lesson takes up 50 minutes. We start every morning with two lessons of what we call Language Study, which will mostly be grammar and vocabulary. The rest of the morning classes are either spent in the computer lab, or in workshops. There抯 a Conversation Workshop to practise your speaking skills, one lesson on Tuesday, directly after the Language Study class and there抯 a Reading Workshop of two times fifty minutes on Friday morning. There are also two fifty minutes classes in the computer lab which form the third class on both Wednesdays and Thursdays.
Lunch is from half past twelve till one o抍lock. Each afternoon, except for Wednesday, starts with two lessons of skills practice. In those classes you will mostly practise listening and speaking. On Monday and Tuesday they are followed by a class of fifty minutes at the language lab.
The language lab is open Monday to Friday from half past eight in the morning until eight o抍lock in the evening, while the library is open every day, including the weekends, from eight am till ten pm.
Language Study and the classes in the computer lab are taught by Dave. Conversation and skills are taught by Flora and Sarah. Reading is taught by Andrew and the teacher who will be with you in the language lab is Julia. If for some reason you cannot come to class, you have to phone your teacher half an hour before class begins.
LISTENING TEXT to Unit Five (for Workbook):
Wales is one of the four countries that form the United Kingdom. The Act of Union in 1536 combined West and East Wales into a single state. Wales was considered by the English and later Great Britain and the United Kingdom governments as a separate part of England and Cardiff was named in 1955 as its capital. Since then we speak of 揈ngland and Wales?where before only 揈ngland?was used.
Travelling from England, you will know when you are in Wales, because all street signs and names of railway stations are written in two languages: English and Welsh. Welsh is the original language of the people in Wales. The landscape in Wales is also different from England. While England is mostly hilly, the central parts of Wales are mountainous. It is here that we find the highest mountain in the UK. As it is impossible to grow crops on the mountains, Welsh farmers keep sheep instead. It is difficult to get around the steep mountain slopes, even in a jeep. So the Welsh sheep farmers use dogs to move the sheep from one field to another.
The weather in Wales is warmer and wetter than in other parts of Britain. This is because of the high mountains. The wind here usually comes from the southwest. As it moves across the warm Atlantic Ocean, the wind carries water from the sea. When this wind hits the mountains of Wales, the air rises causing rain to fall.
Wales is popular with holiday visitors. They go hiking in the mountains, or spend their summer days by the sea, swimming or sailing. People interested in history and architecture can visit some of the many historical sites in Wales. Most ancient castles and churches are open to the public. During the holidays, there are festivals too, with singing and dancing. Wales is often called 搕he Land of Song?and its people are famous for their love of poetry and music.
LISTENING TEXT to Unit Six (for Students?book)
Part 1
Hello! Greetings from the future! My name抯 Mekanika and I live in the year 3044. Well, that抯 what you would call it. We call it the year 58 AL. AL means 揂fter Leaving? You see, 58 years ago, people on the earth decided that they had to do something to save the people on the planet. There were so many people on the earth, and there was so much pollution, that the only way to keep the planet from dying was to send
people into space. My family was one of the chosen ones. About one third of the earth抯 population was left back home, and the rest of us went into space. We抮e now living in a new city on the planet Mars. Life here is very nice, and we are happy in our new home. We still keep in touch with the people on earth and some of us go back for short visits. The earth is better now, and the people back home are doing their best to clean up the planet. I was born here on Mars and I抳e never been to earth. My grandparents and parents tell me about the earth and it sounds like a beautiful place. When my science teacher told me that we could use our school抯 time machine to send messages to the past, I wanted to send one to you and tell you about life here.
Part 2
Every morning, I have to get up at two o抍lock. That probably sounds very strange to you, but, you see, we have a different time system here. We divide the day into eight parts. Two o抍lock in the morning here on Mars is almost like six o抍lock on earth. I eat breakfast with my family before I go to school. The food here is different from your food: we eat pills and drink juice to stay healthy. My history book says that you ate something called bread
and even ate meat from other animals! That sounds very strange to me. We don抰 eat any animals here and I抳e never even seen bread. At three thirty I catch the school spaceship and fly to class. We don抰 have schools and classrooms. We meet our learning guides (you called them teachers) in different places and solve problems together. I love school. My friends are wonderful and I like to think about the world in new ways. I also like creating things with my mind box (you called it a computer). I抦 very interested in what you call 損ainting?and 搒inging? Can you please tell me more about what they are? I抳e read about your life in my history book, but it抯 difficult to understand how you lived such a long time ago. Could you please write to me and tell me about your life? Thank
you. I have to get back to work. I have a test in Mars geography next week, so I need to prepare for it.
Best wishes,
Mekanika
LISTENING TEXT to Unit Six (Workbook)
Here is the news for Saturday, the 14th of April.
The first group of Chinese tourists have returned from the moon. A group of 25 tourists landed last night at the Space Research Centre in Qinghai Province. They had been in space for one week. Their trip included a visit to three different places on the moon. Each of the tourists paid one and a half million yuan for the trip.
Anew speed record had been set for the underground railway that joins Chengdu and Xi抋n. The railway was completed last year. Yesterday a train reached a speed of 821 kilometres per hour. The train was carrying 1,200 passengers. The journey of 842 kilometres took one hour and eleven minutes.
A new type of lemon tree for cold countries has been developed by the Agricultural Research Service of Liaoning Province, where research has been going on for seven years. The new lemon tree will be grown in cold parts of China. Normal lemon trees are killed when the temperature falls below 0 degrees Centigrade.
LISTENING TEXT to Unit Seven (for Students?book)
The Disease Detective
Jane is one of the experts at the Center for Disease Control and Prevention. People at the Center study how diseases start and spread and, as the name shows, try to control and prevent diseases. We asked Jane about her work.
J = Jane; I = Interviewer
Part 1
J: Well, I have to be a detective: I go to a place where a disease has broken out and look for clues about the disease. I try to find as much information as I can about what happened. Who is sick? What are the signs ?do they have a fever, a headache or a sore throat? When did they get sick? When I have collected the information, I use it to find out what caused the problem. We can use what we learn to prevent others from getting sick.
Jane and other disease detectives at the Center do their jobs in different ways. Some detectives work in laboratories where they examine tests and samples. Others travel to towns or villages where there are diseases and talk to people who are sick. All of the experts at the Center know that their work is important. If they do their jobs well, they will save lives.
Part 2
I: How often do you actually go to places where a new disease has broken out?
J: Oh, it happens every now and then. Probably about every three months or so.
I: How do you find out about new diseases?
J: We will usually hear from doctors and hospitals. If they notice anything strange, they will give us a call and ask for help. If we think it is necessary, we抣l go to the place where people are getting sick.
I: Aren抰 you afraid of catching the diseases you are studying?
J: Well, yes, sometimes. But we are always very careful. If you know what you are doing, you can protect yourself. Besides, I抦 more afraid of what might happen if we don抰 find out what kind of disease it is.
What can ordinary people do to protect themselves?
J: The best thing you can do is simply to wash your hands often and try to avoid crowded places. Wearing a mask over your face may help, but it is probably not necessary unless you are caring for a sick person. It is also important to see a doctor if you get sick, so that you don抰 spread a disease without knowing it.
LISTENING TEXT to Unit Seven (Workbook)
K = Ken; W = Dr Watts
Part 1
K: Hello, Pr Watts. Thank you for letting me interview you.
W: You抮e welcome. Now, what would you like to know?
K: Well, my first question is about the name of the disease. What does AIDS stand for?
W: When we talk about AIDS, we often use the term HIV/AIDS. HIV is the virus that causes AIDS. AIDS stands for 揂cquired Immune Deficiency Syndrome?
K: Acquired Immune Deficiency Syndrome. OK, got it. But I抦 not sure I understand what it means.
W: Well, to 揳cquire?something is to get something, so 揳cquired?means that you can get infected with the disease. 揑mmune?comes from 搃mmune system? the system that protects our body from diseases.
K: So 揳cquired immune?tells us that this is a disease that we can get from other people and that has something to do with our immune system. What exactly does AIDS do to our immune system?
W: That抯 what the next word tells us. If something is 揹eficient? it means that it isn抰 functioning properly, it isn抰 working the way it should. So 揳cquired immune deficiency?means that even though we were both with a good immune system, we have now got a disease that breaks down the immune system.
K: Wow, that抯 terrible! So what happens when someone抯 immune system doesn抰 work?
W: Well, to put it simply, he or she gets sick a lot. The last word in AIDS, 搒yndrome? means all the bad things that happen to your body when the immune system doesn抰 work.
Part 2
People who die of AIDS actually don抰 die of AIDS. When a person infected with HIV develops AIDS, he or she easily gets sick. A person with AIDS has a very weak immune system. Many common diseases can be cured in patients whose immune system functions well, but when they enter the body of a person with AIDS, they can kill him or her. Many AIDS patients die of infections or serious colds, but there are also many diseases that we have never heard of. If your immune system is working, they may not be able to do any harm, but because the immune system has been weakened, the diseases can抰 be cured. They will grow stronger and stronger until one day they kill the patient with AIDS. Therefore, much of the treatment an AIDS patient receives is meant to help the body defend itself against diseases.
LISTENING TEXT to Unit Eight (for Students?book)
Two people have just arrived at the hospital, each with a child. A nurse is asking them questions.
Part 1
N = Nurse; F = Father; H = Harry
N: Can I help you?
F: Yes. I wonder if you could look at Harry抯 leg.
N: What抯 the matter with it?
F: He was bitten by a dog yesterday evening. It was bleeding quite badly.
N: Let抯 have a look at it then. I see. What did you do before bringing him here?
F: I washed the wound under running water for a few minutes. Then I dried it with a clean cloth and tied another piece of clean cloth around it.
N: Have you had any pain? Does it hurt?
H: Yes, it does hurt a bit.
N: Was it your dog?
H: No. It belongs to a neighbour.
N: This is very important. The dog must be examined immediately.
F: Why is that? The dog is usually very friendly.
N: If the dog has a disease that makes it bite people, your son could die.
Part 2
N = Nurse; M = Mother
N: Can I help you?
M: Yes. This is my daughter Jill. She抯 two and a half. She抯 drunk some ink.
N: Some ink? When did this happen?
M: About half an hour ago.
N: Did you give her any first aid?
M: No, I didn抰 know what to do. I thought it might be poison so I t9rought her here at once.
N: Have you got the bottle with you?
M: Yes, here it is.
N: Do you know how much she drank?
M: Well, the 1,ottle was almost empty, so I think not very much.
N: Right. I抣l take you to the doctor. Come this way, please.
LISTENING TEXT to Unit Eight (Workbook)
Part 1
C = Police Captain; 0 = Police Officer
C: Johnson, come here, please. I have a job for you.
O: Yes, sir. What抯 happened?
C: There抯 been a traffic accident on West Side. A boy seems to have been hit by a car. Three policemen are there already and there are two eyewitnesses. Please go down there and see if you can find out exactly what happened and who caused the accident.
0: Yes, sir. When did the accident happen?
C: About half past four.
0: And how many people were involved in the accident?
C: Only two, as far as we know. The boy was already sent to hospital with minor injuries:
0: Where are the other policemen?
C: They are by the intersection, on the east side.
Part 2
P = Officer Pei; W = Officer Wang; A = Driver A; B =Woman on bicycle
(Traffic noise in the background; not very loud, but in the pauses the occasional horns or bells can be heard. Driver A is shocked and scared; the woman on the bike is angry and upset.)
P: Miss, please tell me what happened.
B: I was on the eastern side of the crossing, turning north. Ahead of me in the bike lane was the poor boy. He was crossing the street to go to the western side when that man just ran straight into him. Oh, it was awful!
P: Can you please tell me what the car was doing?
B: It was waiting to turn right.
P: I see. Where was the boy?
B: He was standing behind the white line in the bike lane, waiting for the light to turn.
P: Was he moving when the car hit him?
B: No. He was just standing there. Poor boy! The car was moving much too fast and the driver didn抰 even look to see where he was going!
W: Sir, please tell me what happened.
A: Oh, it was terrible! I抦 so sorry. It wasn抰 my fault!
W: We抣l see about that later. Please just tell me what happened.
A: I was waiting on the eastern side. I was turning right, heading north. I started turning right and suddenly this boy ran out in front of me on his bike. I had no time to stop. there was nothing I could do.
W: Did you see the boy before you turned?
A: No, no! He must have been riding too fast. There was no one waiting to cross the street when I looked.
W: How fast would you say you were going?
A: Oh, not very fast. I had stopped and was just beginning to turn when I hit the boy. Really, you know how boys are ?they don抰 watch where they抮e going!
LISTENING TEXT to Unit Nine (for Students?book )
Part 1
Ladies and Gentlemen,
Today we are celebrating Earth Day. Earth Day is a day for reflection and action. Today, people in countries all over the world get together to discuss the earth and our future, and to take action to improve the current situation. Earth Day is a chance for us to learn about the world and change our behaviour. It helps me understand that we must act. If I had known more about the earth in the past, I would have made different choices about what to do and what to buy. It is never too late to change. I am here today to talk about one of the most important problems we are facing. In my view, the most important challenge ahead of us is to find a way to protect the water on our planet. 75% of the earth is covered by rivers, lakes and oceans, so it is truly a water planet.
Unfortunately, most of the water cannot be used for drinking. The earth is already becoming a thirsty planet, but there is still time to do something about the problem. If we want to have enough water in the future, we must learn to take better care of our water. We must stop polluting our water. We must learn to save water in our daily life.
Part 2
We should take better care of our water. Most of the fresh water on the earth is being used for farming. We use clean water to grow food. We need food, of course, but we must be more careful when we use our water. Too much water is being wasted because we are using old ways of watering our plants. We must solve this problem if we want to have enough water in the future. The best way to solve the problem is to use the knowledge and technology that some countries have already developed. If we work together and share what we know, we will be building a better future for all of us.
We must stop polluting our water. Even if we succeed in making more water available to us, we must still do something about water pollution. We are polluting water at an alarming pace. Cars, factories, and air conditioners pollute the air and the water. We must change the way we think and the way we live. Let抯 not drive if we can walk or ride a bike. Let抯 try not to use air conditioners more than what is absolutely necessary. Let抯 not buy products that cause pollution. Let抯 make new rules and use new technology to make sure that factories are green and clean. Keep in mind that we ?you and I ?are the ones who must change. This brings me to my final point: we must stop using too much water in our daily life.
LISTENING TEXT to Unit Nine (for Integrating Skills )
Speech 1
Hi. We are three children from three different continents and we抎 like to tell you what we think about the environment. The children of the world are disappointed because too many adults are too interested in money and wealth to take notice of serious problems that affect our future. Young people from all over the world have many things to say about the environment, but we all agree on one serious problem most leaders don抰 listen. We are here today because we want you to listen ?to listen to everybody.
Here抯 what the children of the world are saying:
Governments of the world must:
?make sure that all people from developing countries
have free access to clean drinking water;
?limit the number of cars per family;
?stop cutting down trees without replacing them.
People of the world must:
?make use of alternative transportation such as walking, biking and car-pooling;
?reduce, reuse, and recycle as much as possible.
We are worried that many governments listen too much to those who care very little for the environment and people. Remember, we cannot buy another planet, and our lives and those of future generations depend on this. We are not asking too much! You said this Summit is about taking action! We need more than your applause and comments of 搘ell done?or 揼ood speech? We need ACTION!
Thanks for having us here and for listening to the voices of children.
Speech 2
Ladies and Gentlemen,
Thank you for giving me the opportunity to speak to
you today. I wish, however, we could do more than just talk. The Earth Summit is not just about good speeches and big words; it is about doing something about the problems we are facing. I will try to do something right now, right here. That抯 why I have brought this big bag. What do you think is in it? Well, I抣l show you. Yes, that抯 right, rubbish! On my way over here, I picked up the rubbish I saw in rubbish bins on the street so that I could talk to you about what rubbish really is. Some of you might think that rubbish is what we throw away, something useless that only causes problems. Well, I say that that抯 rubbish. Let me explain what I mean. What is really in this bag? Resources, possibilities, money, jobs and solutions! What we call rubbish today is actually the resources of tomorrow. Let me tell you how we can use rubbish ?some left-over food, a milk carton, and an empty bottle ?to make the future greener, cleaner, and better, and to make money.
LISTENING TEXT to Unit Nine (Workbook)
1= Interviewer; C = Carl
Part 1
I: Can you tell me about the project you worked on in Egypt?
C: Egypt has developed a large programme to clean up and protect its water. One of the projects is to help small farmers build small channels to make sure that the water supplied by the government can be used in the best way possible.
I: So what was the problem?
C: It was often difficult for farmers to keep the channels clean and in good order. The channels were used as rubbish bins and too many plants grew where the water should flow.
I: How did you solve the problem?
C: At first, we thought that the farmers simply didn抰 understand the situation and that we could solve the problem by educating them. But just to make sure, we interviewed some farmers and observed what they were doing.
I: What did you do to learn more about the farmers and their work?
C: Well, we visited many farmers and their families. We also formed small discussion groups in which we talked about the problem and what could be done about it.
I: What did the farmers think and do?
C: We found that the farmers did know a1抩ut the problem and had paid a company to clean the channels. But they didn抰 do it often enough.
Part 2
I Why didn抰 the farmers clean the channels often enough?
C They thought that the government was responsible for the channels and they only cleaned them up when there was too much rubbish. They felt that this was unfair and didn抰 believe what the government said.
I: And how did the government react to this?
C: Well, they were very surprised. They decided to show the farmers that they were serious about the problem. Farmers and the government would work together. The farmers formed a group that would oversee the work. A special channel cleaning day was chosen and the farmers and the government decided to share the costs. The farmers would pay for the cleaning equipment and the government would pay for taking the rubbish away.
I: That sounds like a good solution.
C: It was. Working together also gave people a chance to understand the dangers of throwing rubbish in the channels. It stopped the water from flowing and made it dangerous for children to swim in the channel and for women to use the water at home.
I: Were the farmers happy about the solution?
C: Yes, they were. The project was a success. By working together, more things were achieved and everybody learnt from the experience.
LISTENING TEXT to Unit Ten (for Students?book)
And now the weather forecast for Tuesday, June 24. Cooler and drier air over the Northwest will advance towards the East on Tuesday. But as it does so, it will meet with warm and moist air already in place resulting in showers and thunderstorms.
Thunderstorms are possible in areas from the Southern states to the Northeastern states where we might see some pretty bad weather, with wet snow and strong winds, perhaps even some storms.
The showers and thunderstorms that hit the Midwest on Monday may still be around part of Tuesday, but will disappear during the afternoon.
Comfortable temperatures around 75 degrees are forecast for the South, 68 to 72 for the Midwest and similar temperatures for the Northeast, while higher temperatures, up to 88 will be found in the east along the coast. While the Southwest may see some rain or even thunderstorms, the rest of the West will be hot with temperatures over 100 degrees and no hope of a cooling shower. Far to the Southeast, the storm, which had looked as if it would grow into a hurricane, fell apart on Monday. This year has already seen an unusually high number of hurricanes. Hurricane Danny in the Atlantic Ocean last week has put in third place behind and 1959 for having the most tropical storms or hurricanes this early in the season. The fourth storm usually arrives towards the end of August, so Danny, formed on Wednesday, came a month and a half early.
If the fifth named storm - the 揈?storm - develops before July 22, this year will have the hurricane season with the fastest start. Its name would be Erika. The hurricane season is from June 1 till the end of November. A typical Atlantic hurricane season has 10 named storms, six hurricanes and two major hurricanes. The latter can be a real disaster when they hit the coast. Tropical storms such as hurricanes and typhoons are given names to avoid confusion. Their names start with letters in the order of the alphabet. The first five storms in will be named Arlene, Bret, Cindy, Dennis and Emily.
LISTENING TEXT to Ten (for Workbook)
K = Kate L = Linda
K: Hi, Linda, how抯 your life in Taiwan? Po you like it there?
L: It抯 fine, Kate. Thanks. Bill and I like China very much.
K: I抳e heard that Taiwan is quite often hit by typhoons. How do you feel about that?
L: That抯 right. They are quite common between the months of May and November.
K: Terrible. I would not want to live in a place like that.
L: Oh well. You抣l get used to it. With a Ht of common sense and taking the right measures, typhoons need not l2e a Hg problem.
K: So what should you do when you know a typhoon is coming up?
L: You should always keep some plastic sheets ready to cover furniture. Important papers are best kept in plastic boxes or bags that don抰 let any water through. Buy some extra food in metal or in glass containers, and keep a torch, batteries, a first-aid kit, a radio and such things ready.
K: What else do you do when you know there will be another typhoon?
L: If a typhoon is expected to hit within 24 to 48 hours, you should make some extra ice to keep food cooled when the electricity falls away. Fill the bath with water for cooking, and make sure there is enough drinking water; move furniture away from windows; put loose objects, such as furniture and plants in pots, baskets or boxes from the balcony and the yard into the shed. You must close the curtains and take shelter where you cannot be hit by glass that is flying around, for example the hall or a room without windows.
K: Have you ever experienced a big one?
L: Oh, yes. It was a very frightening experience.
K: What happened?
L: When the storm hit, we heard all the windows breaking and furniture being pushed around. The roof made a cracking noise. We thought it would be blown away. Then the storm seemed to die down. But it was the eye of the storm. A few minutes later it came back with full force. I was afraid the whole house would be swept away.
K: Have you thought of moving to another part of the country, where there are fewer natural disasters such as earthquakes and typhoons?
1.理解点电荷的概念。
2.通过对演示实验的观察和思去向不明，概括出两个点电荷之间的作用规律。掌握库仑定律。
过程与方法：
1.观察演示实验，培养学生观察、总结的能力。
2.通过点电荷模型的建立，了解理想模型方法，把复杂问题简单化的途径，知道从现实生活的情景中如何提取有效信息，达到忽略
次要矛盾，抓住主要矛盾，直指问题核心的目标。
情景引入
为了测定水分子是极性分子还是非极性分子，可做如下实验：在酸性滴定管中注入适当蒸馏水，打开活塞，让水慢慢如线状流下，把用丝绸摩擦过的玻璃棒接近水流，发现水流向靠近玻璃棒的方向偏转，这证明水分子是极性分子，聪明的同学，根据上述素材，你想知道是如何证明水分子是极性分子吗?
(同性相斥，异性相吸)，带正电的一端远离玻璃棒。而水分子两极的电荷量相等，这就使带正电的玻璃棒对水分子显负电的一端的引力大于对水分子显正电的一端的斥力，因此水分子所受的合力指向玻璃棒，故水流向靠近玻璃棒方向偏转.
问题探究
知识点一、点电荷
走进生活
验电器的上部是球形的金属导体，中央金属箔是指针式的形状，电荷分布与带电体的形状有关，与万有引力相似，带电体间的相互作用力与带电体的形状和大小有关。为了研究的方便，在应用万有引力定律时，我们引入了质点的概念，利用万有引力定律就能求出两质点间的万有引力大小，如果带电体也能等效成电荷全部集中在一个几何点上，研究带电体间的相互作用力也会变得相对简单。回顾学过的质点概念，你能建立起点电荷的概念吗?
自主探究
1.点电荷
(1)点电荷是实际带电体的一种理想化的模型。
(2)一个带电体能否看作点电荷主要看其形状和大小对所研究的问题影响大不大，如果属于无关或次要因素时，或者说，它本身的大小比起它到其他带电体的距离小得多，即可把带电体看作点电荷。
(3)对于带电体能否被看作点电荷，一定要具体问题具体分析，即使对同一带电体，在有些情况下可以看作质点，而在有些情况下又不能被看作质点.
2.理想化的模型到简化，这是一种重要的科学研究方法。
各个击破
1.对点电荷概念的解读：
(1)点电荷是一个忽略大小和形状的几何点，电荷的全部质量全部集中在这个几何点上。
(2)事实上，任何带电体都有大小和形状，真正的点电荷是不存在的，它是一个理想化模型。
(3)如果带电体本身的几何线度比起它们之间的距离小得多，带电体的形状、大小和电荷分布对带电体之间的相互作用的影响可以忽略不计，在此情况下，我们可以把带电体抽象成点电荷，可以理解为带电的质点。
2.对点电荷的应用：
有一种特殊情况，均匀带电的球体或均匀带电的球面，带电体本身的几何线度可能并不比它们之间的距离小很多，但带电体电荷分布具有对称性，对外所表现的电特性跟一个等效于球心的点电荷的电特性相同，所以均匀带电的球体或均匀带电的球面都可以等效为一个球心处的点电荷，就是通常所说的带电小球。
互动空间
讨论与交流：
(1)几个同学在一起讨论带电体的大小和能否看成点电荷有什么关系?
答案：不能简单的认为很小的带电体就可以看作点电荷，很大的带电体就不能看作点电荷。
(2)甲同学认为一个带电体有时可看成点电荷，有时不能看成点电荷，你认为这种说法对吗?为什么?
答案：该同学说法正确。能否看成点电荷，关键是带电体的形状、大小和电荷分布对带电体之间的相互作用的影响是否可以忽略不计。
(3)乙同学认为点电荷是一个理想化的模型，所以点电荷没有大小，没有质量，你认为这种说法对吗?
答案：点电荷就是对实际带电体的近似，是一个理想化模型，严格意义上讲点电荷实际是不存在的。所谓“理想化”，就是忽略了它的大小、形状、电荷分布情况，却在一个几何点上具有物体的全部质量，全部电荷量;所谓“模型”，是因为它可以代表原来的真实带电体，在空间占一定大小。
例1.某同学认为带电体能否看成点电荷跟所研究问题有着直接关系，请你根据点电荷的定义判断下列说法正确的是
A.因为电子非常小，所以电子才可以看成是点电荷
B.研究验电器金属箔张开的角度时，可以把两金属箔看成是点电荷
C.在研究相距较远的两个带电小球的静电力时可以把带电小球看成是点电荷
D.任何情况下不规则的带电体都不能看成是点电荷
阅读与理解：根据点电荷定义可知，对于一个带电体，如果其大小和形状跟所研究问题无关，就可以看作点电荷。
属箔不可看成点电荷，B错;相距较远的两个带电小球，可看作球心处的点电荷，C对;能否看成点电荷，与带电体形状规则与否无关，D错.
答案：C
过程与方法：点电荷概念的引入是为了抓住影响电荷间相互作用力的主要因素，忽略次要因素。点电荷是一个抽象的物理模型，能否看作点电荷关键是要看物体的大小、形状在所研究的问题中可不可以忽略不计。能否用一个包含带电体的所有质量、所有带电量的几何点来代替整个带电体，抓住主要因素，并且使问题得以简化，这才是把带电体看作点电荷的意义。
针对训练1.下列说法正确的是()
A.带电量小的带电体都可看作点电荷
B.带电球体都能看作点电荷
C.带电体的电荷分布不均匀，也可以看作点电荷
D.如果带电体的形状和大小在所研究的问题中属于无关或次要因素，就可以把带电体看作点电荷
解析：带电体能否看成点电荷是由问题的性质决定的，与物体的大小、所带电量无关，A错。带电球体相距较近时，电荷的分布会受影响而不再是均匀的，此时不能看作点电荷，B错。带电体大小和形状可以忽略，即使电荷分布不均匀，也能看作点电荷，C、D正确。
答案：CD
即时反馈参考答案
1.不能简单的认为很小的带电体就可以看作点电荷，很大的带电体就不能看作点电荷;
2.同一个带电体在有些情况下可以看成点电荷，而在另一些情况下又不能看成点电荷。关键是带电体的形状、大小和电荷分布对带电体之间的相互作用的影响可以忽略不计.
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