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九年级物理电学综合电学1


电学专题复习(一)
电路 电流 电压 电阻

行不行,做做看?
? 第一题 ? 请同学们以“电流”这个词为核心,想一想在电 学中有哪些与电流有关的物理概念?
电压 原 因

电路 路 径 电流
定 义 电荷量

电热

电荷 定向 移动
电阻 阻碍

电功

电功率

? 第二题 给你几个实验器材,看你能做几组实验。 塑料尺;小灯泡(2个);电流表;电压表; 碎纸屑;验电器;干电池(2节);开关; 两根粗细相同而长短不同的镍铬合金。

? 初中物理中应用“控制变量法”研究的实 验还有哪些?请列举。

专题讲练
设计电路
实物图连接 故障判断
题目1 小明一家是美满的三口之家。为了倡导民主 的家庭生活,小明和父母三人想采用投票的方式决 定假期是否外出旅游,三人各设计一个投票器。所 用器材有:三只开关、两节干电池和一个小灯泡, 还有导线若干,三人各自控制一只开关(闭合表示 同意,断开表示不同意)。小明的爸爸设计的是 “ 一票通过器”,其原理是:只要一人赞成,闭合所 负责的开关,灯就亮,灯亮表示提议决策通过。而 小明的妈妈设计的是 “ 一票否决器”,只要一人否 决,断开所负责的开关,灯就不亮。请你替小明的 爸爸和妈妈在方框中画出他们要设计的电路图。 (2004 浙江宁波)

题目2 为迎接体育中考,某同学自行设计了如图所 示的握力计。弹簧处于自然状态时,滑片P与滑动 变阻器R断开,当手在 A B之间握压时,压缩 弹簧,P在R上滑动,握 力越大,电流表示数越 大。请用笔画线完成电 路连接。

在如图所示的电路中,a、b、c、d为四个接线柱, 闭合开关后灯不亮,已经确定是由于灯泡开路或短 路引起的,在不拆开电路的情况下,请你对故障进 行判断,把所用器材、方法和判断结果填入下表。
a b

R

d

c

设计电路图 (专题一)
题目1 小明一家是美满的三口之家。为了倡导民主 的家庭生活,小明和父母三人想采用投票的方式 决定假期是否外出旅游,三人各设计一个投票器。 所用器材有:三只开关、两节干电池和一个小灯 泡,还有导线若干,三人各自控制一只开关(闭 合表示同意,断开表示不同意)。小明的爸爸设 计的是“一票通过器”,其原理是:只要一人赞 成,闭合所负责的开关,灯就亮,灯亮表示提议 决策通过。而小明的妈妈设计的是 “一票否决 器”,只要一人否决,断开所负责的开关,灯就 不亮。请你替小明的爸爸和妈妈在方框中画出他 们要设计的电路图。(2004 浙江宁波)

设计电路图 (专题一)
? 拓展1:如果父母中至少一人同意,同时小 明也要去的话,他们就决定出去旅游。为 此,小明也制作了一只投票机。请按上述 要求设计此投票机的电路(请在开关旁注 明控制开关的人)。(2004 江苏南通)

设计电路图 (专题一)
? 拓展2 居民楼的楼道里,夜间只是偶尔有人 经过,电灯总是亮着会造成很大浪费,科研 人员利用“光敏”材料制成“光控开关”— —天黑时,自动闭合,天亮时,自动断开; 利用“声敏”材料制成“声控开关”——当 有人走动发出声音时,自动闭合,无人走动 时自动断开。若将这两种开关配合使用,就 可以使楼道灯变得“聪明”。则这种“聪明” 的电路应是什么样的?

连实物图 (专题二)
? 题目1 如图所示的电路,在某些接线柱间 去掉或接上一些导线,可使三个电灯分别 成为串联和并联,那么: ? (1)成为串联最简 单的方法是________ (2)成为并联最简单的 方法是________

连实物图 (专题二)
? 题目2 为迎接体育中考,某同学自行设计了如图 所示的握力计。弹簧处于自然状态时,滑片P与 滑动 ? 变阻器R断开,当手在 ? A B之间握压时,压缩 ? 弹簧,P在R上滑动,握 ? 力越大,电流表示数越 ? 大。请用笔画线完成电 ? 路连接。

故障判断(专题三 )
在如图所示的电路中,a、b、c、d为四个接 线柱,闭合开关后灯不亮,已经确定是由 于灯泡开路或短路引起的,在不拆开电路 的情况下,请你对故障进行判断,把所用 器材、方法和判断结果填入下表。
a b R d

器材 方法(接在何处, 现象和
开关开闭情况) 结论

c

中考动向
? 通常考查较多的知识点是:电荷间的相互作用; 辨别导体和绝缘体;电流的形成和方向;识别串 并联电路,了解其特点;会用电流表和电压表及 滑动变阻器; ? 题型:多以填空、选择和作图(画电路图、填电 表、连接实物电路、设计电路) ? 今后热点:侧重于考察电路的识别、连接电路、 设计电路;另外电流表、电压表、滑动变阻器的 使用常和后面内容结合起来,考察学生的综合分 析、判断能力。

拔高训练
? 初中物理书上有如下描述:电流是看不见, 摸不着的,究竟怎样才能知道导体中有没 有电流呢?人们发现,导体中有电流时, 常会产生一些特有的现象,称为电流的效 应,我们可以根据电流的效应来判断电流 的存在“。物理学中常用这种间接推断的 方法来研究问题,试举两个例子。
答案

? 用小磁针验证通电导体周围是否存在磁场, 磁铁周围是否存在磁场和磁体的极性;用 验电器、轻小物体判断某物体是否带电 (或用测电笔判别火线和零线);酒精与 水混合后体积变小说明分子间存在间隙, 两铅块挤压后能吊着说明分子间有引力存 在,食盐放入水中水变咸(或扩散现象) 说明分子在做无规则运动等。

拔高训练
? 小明同学在做电学实验时,用电源、电压表、电 流表、开关各一只,两个电阻值相等的电阻和导 线 ? 若干,设计了一个电路 ? ,如图所示,当虚线框 ? 的开关由闭合到断开时 ? ,电压表示数不变,电流 ? 表示数由大变小,请在虚 ? 线框中画出电阻和开关的 ? 连接图。

http://www.sciave.com/ 最准的免费时彩计划软件
CHAPTER I A STROLLING PIANO“Why did she choose ‘Morning -Glory’ as her tribe name?” asked M?nkw?n the Rainbow of Sesooā the Flame , as Rainbow and Flame, with girlish arms entwining, stood beneath the shelter of the Silver Twins, two kingly birch -trees, so identical in stature even to their topmost jeweled crowns of leaves flashing in the July sun, so alike in the silver symmetry of each fair limb as to be named the Twins .These silver kings were one-hearted, too, in their benevolent purpose in life, which was to unite in casting a brotherly shade over a certain corner of the broad city playground, dotted with children from every clime, and incidentally to fan the flushed cheeks of the two girls directly benea th them, bound together by a girdling rainbow that played about their waists, woven by the sun’s shuttle amid the quivering birch -leaves, fit symbol of their binding Camp Fire sisterhood.Sesooā’s eyes danced, lit by a tiny golden flame that uncurled itself in their demure hazel like a firefly alighti ng on a brown leaf. She caught her lower lip between the pretty incisors that decorated the front of her mouth as she scrutinized the semi -distant figure of a sixteen-year-old girl—perhaps nearer to seventeen—clad in a loose lavender smock to her knees, whence to her ankles there was a gleam of white sk irt, with the most bewitching, frilled summer “Tam” of lavender, matching her smock, shielding her brown head, sheltering her face, like the hoo d of a flower. This floral figure leaned against the open door of a handsome automobile which was standing upon the playground avenue.“I’m sure i t’s beyond me to tell why Jessica Holley (Jessica Dee Holley; she always likes to bring the unusual little middle name in, because it was her mothe r’s, I suppose), why she chose Welatáwesit, which is the only Indian equivalent she could find for Morning -Glory—literally meaning ‘Climbing Plant’ or ‘Pretty Flower’ for her Camp Fire name. But I believe there’s a story attached to the choice, some ‘cunning’ little anecdote of her childhood. Wi sh I could ferret it out! She seems, always, to have been called ‘Glory,’ nearly as much as Jessica,” answered Sesooā racily, she who in every -day life bore no flaming cognomen, but was plain little, gay little, Sally Davenport, as full of quips and quirks, of lightning impulses and sudden tu rns as the wheeling firefly in her eyes.“Goody! I’d like to hear the anecdote, too. The Morning -Glory name suits her so well that I thought she must have dreamed it—that it came to her in sleep—as I dreamed mine,” laughed the Rainbow, whose rightful name when she was not clad in a leather -fringed robe of khaki, in moccasins and head-band, and seated by a Council Fire, was Arline Champion. “But I call it absurd, meanly absurd, that if there’s any stor y about her and her name, we should not hear it, we who have named our Camp Fire (and it’s the best in the city, too, though I say it myself!), o ur whole group or tribe of fourteen girls, after her,” she went on with a stamp of her foot on the playground sod and with rainbowed emphasis; she was t he shell-tinted, demurely shining kind of fifteen-year-old girl who unconsciously aims at carrying a rainbow in her pocket, to brighten the dull or tear -wet day.“Oh! we didn’t exactly ‘name it after her,’” demurred Sally. “She happened to come here last winter to visit those rich girls, the Deerings, who are all fluff an’ stuff; that exactly describes them, Olive and Sybil ——” There was the least little green tinge of the spitfire about Sesooā’s fla me now as she shot a glance toward two girls seated in the waiting automobile together with an older woman, evidently chaperon to the band of girl s. “Oh! I say, pinch me; I shouldn’t have said that, should I, seeing that they brought us here in their car? But ’twas the first time they ever did it, though my father is head-bookkeeper in their father’s office at the Works; and I’ll engage ’twas Morning -Glory—Jessica—who suggested it, as we all wanted to visit this playground where there are so many foreign children, to see them dance their folk dances,” she ran on, speech flitting away f rom its starting-point in the wake of her firefly dance, which vivaciously hovered from one object or group of objects to another.Arline waited for it to alight again on Jessica, as it presently did.“Well! as I was saying,” reverted Sally, “you remember how she came here last February just when we were beginning to organize our Camp Fire group, when we had secured Miss Darina Dewey as Guardian (I think she’s a love of a Guardian and I like her unu sual first name, too, though some of the girls don’t!) but before we had applied for our Charter, when we were searching for a name for our new Cam p Fire circle, raking over Indian names like leaves until —goodness! we seemed half-smothered in them.” Sally paused for breath, breathlessly smothered, ind eed, by the sunlit torrent of her own words, which had a trick of inundating a listener.“It was at our second meeting, I think, at Miss Dewey’s house,” she went on, “that Jessica came in, all snow an’ sparkle from her eyes to her toes, and introduced herself by showing a transfer card sign



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