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【實(shí)驗(yàn)指導(dǎo)】新版教科版小學(xué)科學(xué)四年級(jí)下冊(cè)2.7電路中的開關(guān)
實(shí)驗(yàn)：做個(gè)小開關(guān)
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實(shí)驗(yàn)材料：橡皮、圖釘和回形針
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實(shí)驗(yàn)方法：
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1、把回形針伸開放在橡皮上，用?筆在伸開的回形針兩端各描一個(gè)點(diǎn)作為標(biāo)記。
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2、先把一枚圖釘固定在橡皮的一個(gè)描點(diǎn)上，再用圖釘把回形針大的一端固定在橡皮的另外一個(gè)描點(diǎn)上。
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3、把橡皮回形針開關(guān)連接到電路中，看看它能不能控制小燈泡的亮與不亮。
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實(shí)驗(yàn)結(jié)論：我們?cè)谠O(shè)計(jì)制作小開關(guān)的過程中，不僅需要使用絕緣體材料，
還需要使用導(dǎo)體材料，導(dǎo)體負(fù)責(zé)接通電路，絕緣體負(fù)責(zé)斷開電路。
(?http:?/??/?mp.weixin.?/?s?__biz=MzI4NjA0NDk1Nw==&mid=2247489862&idx=2&sn=3bf254763f8919f84a8250187e5d7f1f&chksm=ebe3bf34dc9436225e6b798afa71eaade28623958896173fc4c15a86fa07fc77792bd84de053&scene=21"
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理解與應(yīng)用
1.不要用濕布擦，也不能用濕手觸摸電器和開關(guān)。
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2.我們要好好保護(hù)絕緣體。
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3.開關(guān)是控制電流通斷的。開關(guān)必須用導(dǎo)體和絕緣體兩種材料組成，開關(guān)的種類非常多，有門鈴開關(guān)，閘刀開關(guān)、電扇開關(guān)、電燈開關(guān)等。
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4.電路中的開關(guān)（又叫電鍵）起控制電路
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"https:?/??/?mp.weixin.?/?_blank?)通和斷的作用。一個(gè)開關(guān)中，塑料是絕緣體，金屬是導(dǎo)體。
精煉反饋
1.下列材料能制成小開關(guān)的是(?
?
?
?)。
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A.干木塊和鐵絲
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B.鐵絲和回形針
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C.鐵片和相片
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【答案】A
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【詳解】開關(guān)需要的材料有導(dǎo)體做的連接器以及絕緣體做的底座，所以需要的材料就是導(dǎo)體和絕緣體的組合。對(duì)選項(xiàng)進(jìn)行分析，就是A選項(xiàng)的干木塊與鐵絲符合選項(xiàng)。
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2.下列屬于非接觸式開關(guān)的是(?
?
?
?
)。
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A.遙控開關(guān)
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B.墻上的電燈開關(guān)
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C.按鍵開關(guān)
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【答案】A
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【詳解】根據(jù)對(duì)選項(xiàng)的分析，可知遙控開關(guān)屬于非接觸式的開關(guān)。而墻上的電燈開關(guān)和按鍵開關(guān)都是接觸式開關(guān)。所以題目的答案是A選項(xiàng)。
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