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九年级物理电动机转动的猜想


生活中带电动机 的电器

用电器通电后为什么能够转动呢?是 什么带动机械转动的?

提出问题
【对比猜想】
磁体对磁体作用
N S

磁体对电流作用

科 磁场对电流有没有作用(即磁体 学 产生的磁场对电流有没有力的作用?) 探 1、同学们请猜一猜?(并说出依据) 究 2、如何来验证你的猜测呢? 1(如何设计实验方案?需要什么器材?)

实验探究

1.通电导体在磁场里的作 用

实验表明:通电导体如果在磁场里, 就会受到力的作用

思考并探究2:通电导体在磁场里是
不是永远向一个方向运动?若不是,那 它与什么因素有关呢? 1、同学们请猜一猜?(并说出依据) 2、如何来验证你的猜测?

结论:
通电导体在磁场里受到的力的方 向跟电流方向和磁极方向有关。

实验探究

2.通电导体在磁场里受力方向与哪些因素有关?

点击图片

实验表明:通电导体在磁场里受力方向 与电流方向和磁感线方向有关

科学探究3:如果把一只通电线圈放到
磁场中,它又将怎样呢?(猜一猜?)

通电导体和通电线圈在磁场里受 到力的作用而发生运动的时候,消耗 机械能 了 电能 ,获得了 , 即 电能 转化为 机械能 .

探究新问题:
上述实验中,通电线圈能否一直转动 下去 , 若要使它一直转动下去 , 你设想可 采用哪些方法?
这个问题我们下节课进行探究





1. 课后思考通电线圈能否一直转动下 去,如何让电动机使它一直转动下 去,请同学设想可采用哪些方法? 2. 课外活动:制作一台简易电动机。 3. 完成对应配套的练习题。

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 skirt, 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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