第一篇:物理八下期末复习总结
本章从电压入手,引导学生利用电压表来探究串联,并联电路中的电压规律,运用“控制变量法”研究电阻与其影响因素之间的关系,初步了解半导体,超导体的一些特点,会正确把滑动变阻器连入电路中并用其来改变电路中的电流和电压,本章内容是学习电学知识,掌握欧姆定律的基础。
电压和电阻
电压
作用:电压是使电路形成电流的原因
常用单位以及换算:千伏,毫伏,微伏1kv=1000v1v=1000mv1mv=1000uv
电压的测量——电压表
1读数:看清量程,弄清每大格和每小格表示电压数
2接法:并联在被测电路两端,使标有﹣号的接线柱接电源的负极,标有﹢号的接线柱接电源的正极,被测电压不超过电压表的量程
串联,并联电路电压的规律
串联电路中总电压等于各部分电路
中分电压之和
并联电路中各支路两端电压都相等
电阻
电阻的意义:一切导体都具有阻碍电流作用的性质,不同的导体对电流阻碍作用不同
单位:欧姆ω,其他常用的单位:兆欧mω、千欧kω1mω=1000klω=1000000ω
影响电阻大小的因素:长度、材料、横截面积、温度
半导体、超导体的特点:半导体随慰藉条件的改变它的电阻也改变(压敏电阻、光敏电阻等)
变阻器
原理:改变接入电路中电阻丝的长度来改变电路中的电阻
构造:支架、电阻丝、瓷筒、金属棒等
使用方法:“一上一下”
第七章知识总结与能力整合
本章直接从研究电流与电压,电阻的关系切入,引导学生探究电流与电压,电阻之间的关系,得出重要的电学定律——欧姆定律,并进一步运用欧姆定律进行简单的电学定量计算,得出电阻串联,电阻并联的关系,以欧姆定律为理论基础,运用相应的实验器材设计实验测量小灯泡的电阻,运用欧姆定律分析了一些与安全用电有关的现象,认识断路和短路现象,加深对欧姆定律的理解,提高了学生运用知识解决实际问题的能力,激发学生学习物理的积极性
欧姆定律
电阻上的电流跟电压的关系:导体中通过的电流与这段导体两端的电压成正比
内容:导体中通过的电流跟这段导体两端的电压成正比,与电阻成反比
表达式:i=u/r
应用求电流,电压,电阻
测量小灯泡的电阻
原理:r=u/i
方法:伏安法测电阻
注意:小灯泡的电阻太小会随灯丝温度的升高而增大
安全用电
电压越高越危险
断路,短路的认识
注意防雷,正确使用避雷针
第八章知识总结与能力整合
本章是在学习欧姆定律长的基础上,吧对于电学的研究扩展到电能和电功率,是初中物理的重点章节之一,也是难点之一,本章学习的主要目标是让学生了解电能和电功率的概念,知道焦耳定律以及与电功率有关的安全用电方面的问题,整章教材的结构是围绕电能的概念展开的。
电功率
电能
电能的获得:电能是由自然界中各种其他形式的能转化而来的,是由电源(发电机、电池等)提供的
单位:焦耳j、千瓦时kw•h,千瓦时在日常生活中也叫度
1kw•h=1度=3.6*10^6j
电能表
作用:用来测量用电器在一段时间内消耗的电能
测量方法:电能表的计数器上前后两次读数之差
表盘上参数的含义:例如,2500rews/kw•h表示每消耗1kw•h的电能,电能表转盘转2500转
电功
实质:电流做功德过程实质上就是电能转化成其他形式能的过程,有多少电能转化成其他形式的能,电流就做了多少功。
单位:与电能的单位一样,都是焦耳j
计算:w=p•t
电功率
物理意义:表示消耗电能的快慢,符号用p表示
定义:一个用电器功率的大小等于它在1秒内所消耗的电能,用公式p=w/t表示
单位:瓦特w、千瓦kw,1kw=10^3w(1w=1j/1s=1j/s)
千瓦时的来世:1千瓦时是功率为1kw的用电器使用1h所消耗的电能,1kw•h=1kw*1h
额定电压及额定功率:用电器正常工作时的电压叫做额定电压,用电器在额定电压下的功率叫用电器的额定功率。一般来说,在用电器铭牌上标明的电压和电功率就是这个用电器的额定电压和额定功率
测量:原理(p=ui),器材,电路图
电流的热效应
电流的热效应:电流通过道题是,电能要转化成热,这种现象叫电流的热效应,任何导体中有电流通过时,道题都要发热
焦耳定律的内容及表达式:q=i^2rt
电热的利用和防止
电功率和安全用电
电功率与电流的关系:根据公式p=ui得i=p/u可知,由于家庭电路中的电压时一定的,即为220v,所以用电器功率越大,电路中的电流i就越大,为了安全用电,应注意不要让干路中的电流超过家里供电线路和电能表所允许的最大电流值
保险丝
特点:保险丝是用铅锑合金制作的,电阻率大而熔点低
作用:电路中的电流超过允许值时,保险丝能自动熔断而自动切断电路,以保证电路的安全。家庭电路中千万不能用铜丝、铁丝代替保险丝
第九章知识总结与能力整合
本章从生活中常见的磁现象出发,介绍磁的一些基本知识,通过各种探究活动让学生感受到特殊物质“磁场”的存在,并探究“电生磁”和“磁生电”的辩 ……此处隐藏1949个字…… i become a teacher,i will work with childrn.i will be happy.but i won`t be famous.i love children and endlish.however,my english was poor before.for my dream i decided to work hard .i `ve been studying english for two years. i think speaking is the most important in english study. so i often talk with classmates in english.it helped me a lot.i decide to try hard to make my english better.
话题十:到某地的一次旅行及所见所闻three years ago ,i went to beijing with my parents.before it ,i have never been there.in beijing,we vistited many interst of places,for eample,the great wall, tian`anmen square and the summer palace.in tian`anmen square ,there were many tourists there,some were chatting with frineds,some were taking photos.and i met a foreigner.i talked with him in english.he said beijing was very beautiful and chinese people were friendly.i was very happy to hear that.
话题十一:感谢信(教材unit10 p80)
话题十二:准备晚会
范文:today is kelly' s birthday.she is my best friend.i' m going to have a surprise party for her in my house.i invited leina,sally,macia,and many other friends.all of them are teenagers.leina promised to bring some drinks.sally will bring some snacks.david said he would bring some flowers and pictures.i bought a big cake and a present for her.i am going to get ready for a special meal.i bought humburgers,french fries,and i made some salad.kelly likes hamburgers and fruit salad.macia likes cakes and i like french fries.i think all of us will laugh and sing and dance.kelly must be excited. 话题十三:学习英语的方法:dear lin tao,
i am glad to receive your last letter. you want to know how to learn english well. here is my advice:you mustn’t give up .whatever you meet any difficulties that you meet. every day you should spend some time in learning english. remember as many english words as possible and try your best to use them.read english books , magazines or newspapers as often as you can. it is useful and important for you to improve your english. i think listening or singing english songs can make you more interested in english learning.
hope you make great progress in your english learning.yours, zhangpeng 话题十四:致谦信:dear tom,
thank you very much for inviting me to your birthday party.i'd love to go but i can't.my parents are out on business.they are coming back next month.and now i have to look after my grandma because she is ill in bed.and i also need to study for my coming end-of-year exam.i'm very sorry but i can't go to your party.thank you for asking me.i hope you can have a good time.
话题十五:暑假及期末复习星沙英语li ping the summer holidays are coming soon.several days ago ,i was very tired because iwas busy doing a lot of exercises.now i`m having exams.some of my classmats are nervous about the exams,but i`m very happy in a few days,i am going to have a good rest during the holidays. i will go sightseeing. at the same time ,i am also going to visit my friends and relatives. i am sure i will spend my holidays happily.
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