【正文】 述磁場時，磁感線都是從磁體的N極出發(fā)，回到磁體的S極。五、電磁繼電器 揚聲器電磁繼電器繼電器是利用低電壓、弱電流電路的通斷，來間接地控制高電壓、強電流電路的裝置。七、磁生電產(chǎn)生感應(yīng)電流的條件：閉合電路的部分導(dǎo)體在磁場中做切割磁感線的運動。模擬信號在傳輸過程中會丟失信息，而且抗干擾能力不強，保密性也很差，信號衰減厲害。電視信號的傳輸與無線電廣播基本相同，只是發(fā)射部分多了攝像機，攝像機把圖像變成電信號。在地球周圍均勻分布3顆衛(wèi)星，就可以實現(xiàn)全球通信。電能表是測量一段時間內(nèi)消耗的電能多少的儀器。電功率與電能、時間的關(guān)系：P = W / t在使用時，單位要統(tǒng)一，單位有兩種可用：（1）、電功率用瓦（W），電能用焦耳（J），時間用秒（S）；（2）、電功率用千瓦（KW），電能用千瓦時（KWh，度），時間用小時（h）。當(dāng)發(fā)電廠電功率一定，送電電壓與送電電流成反比，輸電時電壓越高，電流就越小。所以在家庭電路中：A、不要同時使用很多大功率用電器；B、不要在同一插座上接入太多的大功率用電器；C、不要用銅絲、鐵絲代替保險絲，而且保險絲應(yīng)該在可用范圍內(nèi)盡量使用細一些的。四、電和熱電流通過導(dǎo)體時電能要轉(zhuǎn)化成熱，這個現(xiàn)象叫電流的熱效應(yīng)。1KW = 103W1馬力 = 735瓦。電能用W表示，常用單位是千瓦時（KWh），在物理學(xué)中能量的通用單位是焦耳（J），簡稱焦。微波大致沿直線傳播，所以每隔50km左右就要建一個微波中繼站。信號的接收由收音機完成。話筒把聲音信號轉(zhuǎn)變成電信號，聽筒把電信號變成聲音信號。電動機是利用通電線圈在磁場里受力而轉(zhuǎn)動的原理制成的。四、電磁鐵1．電磁鐵工作原理：電流的磁效應(yīng)。3．磁化：使原來沒有磁性的物體獲得磁性的過程?；鹁€和零線 用試電筆可以判斷哪條是火線。實際電壓越大，燈泡的實際功率越大；只有在額定電壓下它才能正常發(fā)光，此時的實際功率等于額定功率。第八章 電功率一、電能電燈泡把電能轉(zhuǎn)變?yōu)楣饽?，電動機把電能轉(zhuǎn)變?yōu)閯幽?，電熱器把電能轉(zhuǎn)變?yōu)闊?內(nèi)能)。二、歐姆定律及其應(yīng)用 公式I =三、測量小燈泡的電阻 ：I= ：3．步驟4．本實驗中，滑動變阻器的作用：改變被測電阻兩端的電壓（分壓），同時又保護電路（限流）。否則指針會反偏。1熟練掌握探究串聯(lián)電路和并聯(lián)電路中電流的規(guī)律的方法。1知道電流方向的規(guī)定。能將生活及自然界的一些現(xiàn)象與物質(zhì)的熔點聯(lián)系起來；（三）汽化和液化了解汽化現(xiàn)象和液化現(xiàn)象，知道汽化吸熱，液化放熱；知道什么是沸點，什么是沸騰；能熟練說出探究水的沸騰的實驗過程及沸騰的特點；知道蒸發(fā)現(xiàn)象，了解影響蒸發(fā)快慢的因素，了解蒸發(fā)和沸騰的相同點和不同點能利用液體的沸點知識解釋簡單現(xiàn)象，如分離水和酒精的方法。（三）平面鏡成像了解平面鏡成像的特點。知道聲音傳播的形式。t usually like to be criticized, so we have to be careful how we do ：Could you please put out that cigarette?：Would you mind picking it up?：Sorry, would you mind joining the line?常見動名詞、分詞的習(xí)慣用法總結(jié)使用ing分詞的幾種情況。第三篇：初二英語下冊復(fù)習(xí)提綱(第七單元)Unit 7 Would you mind turning down the music?… down/turn… up 關(guān)小聲/調(diào)大聲音（電器）… on/ turn …off 打開/關(guān)閉（電器） the bike 移動自行車 a minute/right away/in no time 立刻,馬上 late for school/class=arrive late for school 上學(xué)/上課遲到 in line=stand in line 排隊等候 in line=jump a queue 插隊 mad/annoyed 變得生氣 to sb 發(fā)生在…身上 an hour 半小時 first 首先 last=in the end=finally 最后 do /not to do allowed to do /not to do public 當(dāng)眾地；公開地；公然地 public places 在公共場所 the rule 不遵守規(guī)則… up 撿起 …out 熄滅 litter 扔垃圾 the voice down 控制聲音 the dishes on another pair of jeans at a meeting me in the kitchen some posters store…around to be polite in the subway door in line close to.. different ideas about unfortable all situations public places本單元目標(biāo)句型： you mind cleaning the yard? 你介意打掃院子嗎? at 39。so為代詞，用來表示贊同前面所提及的內(nèi)容。對for與since短語提問用how long。 than three quarters of the population are 。Me neither.= Neither/Nor have 。 with a pig isn’t always 。 you mind keeping your voice down? 你介不介意把音量放小呢？ voice: 名詞，指說話和唱歌地嗓音； talk in a loud voice 高聲交談 noise: 名詞，指人們不愿聽到地噪音；sound: 名詞，泛指自然界一切可以聽到的聲音。再看：I wrote a letter to my 。 fact, the first Jews probably came to Kaifeng more than a thousand years ，首批猶太人可能是在一千多年前來到開封的。Would you like some more tea? No ？不再需要。be sure ＋從句，表示句中主語對某事有把握 I am sure（that）he will succeed=He is sure to 。write it/them down類似的短語還有：put on 穿上，上演take off 脫下turn on 打開（電器等）turn off 關(guān)掉 turn up調(diào)大（音量）turn down關(guān)?。ㄒ袅浚﹑ut away 把?收好take away拿走 give back 歸還work out算出 ring up打電話給? find out 查清，查明look up 查找throw away 丟掉think over 仔細考慮 pick up 撿起wake up把?弄醒 6e out出來，出現(xiàn)，（花）開放The flowers start to e out in spring.【搭配】 e along一道走，一起來e after 跟隨，隨?之后，相當(dāng)于followe back回來e up走近，靠近e on表示說話人的一種催促、勸說、鼓勵等“快”、“來吧” 6at a bad/good time of year在一年中不好的/好的時節(jié)里6get “逐漸變得?” get＋天氣，長短get warm/cold/long/short turn“變得?” turn＋顏色 turn green/yellow/red能用做聯(lián)系動詞的還有：look看起來顯得?look worried ,taste嘗起來?taste delicious, smell聞起來?smell good, sound聽起來sound great, feel覺得?feel happy 6the best time to do ?的最好時間It’s the best time to say good 、Late march 三月底early spring初春early in the morning清晨6look unlike 看起來不象 be the most like/unlike 最像/不像 The weather in China is the most unlike that in 、Autumn starts in goes on to Nov.=Autumn lasts from 、later on=at a later time過后，以后He’ll visit the Great Wall later 、do some reading讀書After supper, I did some the north/south/east/west of?在?的北/南/東/西部，在其范圍之內(nèi)。1reply用做名詞，答復(fù) make a reply 作出答復(fù),make no reply沒有答復(fù) reply 用做動詞，回答reply to sb./sth.=answer reply to/answer my question in 、sell sth, to sb.=sell He wants to sell his old bike to me=He wants to sell me his old 、discuss business together一起談生意1by the way順便問一下By the way, why did you call me? 【拓展】 on the/one’s way to?在去某地的途中He is on his way to a/the?way用??方法Can you do it in the same way?1have a problem with?無法解決??的毛病，相當(dāng)于there is something wrong with?Do you have any problems with your TV set?1put?right使??恢復(fù)正常 Can you put the clock right? have a lot of fun（doing）玩得開心We had a lot of fun in the 、do/take exercise=do sports進行運動，鍛煉2plan one’s work carefully精心計劃工作2plan to do are planning to start next 、make a plan for?為?制定計劃You’d better make a plan for your 、drive to ?=go to?by car開車去?He drives to ?開車送某人去?He drives his son to 、have a rest=rest休息He had a rest for an hour=He rested for an 、have a swim=go swimming游泳2go on a trip=have a trip 進行旅行He is going on a trip to Japan.【拓展】 go on with sth.= go on doing （同一件事）go on to do （另一件事）【舉例】After having a cup of tea, he went on with his work/ finished reading and went on to write his 、ask help 向??求助Why not ask the teacher for help? ask question向??提問題ask for came to ask for some ??詢問有關(guān)?的情況 ask sb.（not）to do （不）做某事 He asked me about the weather in asked us to help him with his 、go out for a walk=have a walk=take a walk散步3at breakfast早餐時He read morning paper at breakfast 、say goodbye to向??告別/辭行 say hello to向??打招呼，向??問好 say sorry to向??道歉say good morning to向??問候早安 say thanks to向??道謝3be useful to English is useful to useful for and games are useful for 、have a good/bad/ poor memory有很好/很差/很糟糕的記憶力3all the time總是，一直，常和always做同義詞組替換。I forgot returning the book to the 。Will do 和be going to do的區(qū)別：二者都可以表示將來的動作或狀態(tài)，有時可以互換，但又有區(qū)別。第一篇：初二英語復(fù)習(xí)提綱復(fù)習(xí)要點（U8U14）一、語法：一般過去時態(tài)。一般將來時態(tài)。I forgot to return the book to the ?！九e例】They came to China three years visited him before remember reading the book 、enjoy喜歡，喜愛，相當(dāng)于 like或 love 【搭配】 enjoy ?They enjoy Chinese food very doing ?Do you en