题干

(1)根据如图所示的实物连线图,画出对应的电路图.(要求连线要横平竖直,尽量使电路图简洁美观)

(2)用笔画线代替导线将图7中实物连接完整.要求:
①电压表测量灯泡两端的电压.
②滑动触片向右移动时,通过灯泡电流变大.
③导线不能交叉.

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解:(1)(2)

同类题2

阅读理解

    Durian(榴莲) is probably the smelliest fruit in the world, letting out an unusual unpleasant smell which would make anyone bring up. However, nobody was aware of what gave this fruit its unique smell, so a team of researchers from Singapore decided to take a look at its genome (基因组) and find out,

    Durian is well-known throughout Southeast Asia as the king of fruits, mostly because of its awful appearance and smell. However, the origin of this unpleasant smell was unknown, so researchers decided to map the genome of the fruit, and find the gene that controlled it. A group of genes, volatile sulfur compounds (含硫化合物), became very active in the fruit, and they were found responsible for resulting in the unpleasant smell.

    The fruit confuses everyone with a sulfuric smell, like rotten onions and ingredients. The smell lasts long, mostly because the fruit contains more volatile sulfur compounds. Other species usually benefit from two gene copies at most, but durian has four, leading to the striking smell.

    However, this smell might be an advantage for durian in the wild. Although we find it unpleasant, many animals might be attracted by it. If they eat the fruit, then they can easily spread its seeds everywhere, thus contributing to the distribution of the species.

    The mapping of the durian genome also showed some other information on the species. First of all, the fruit has an impressive number of genes, namely 46,000. Also, with the help of these genes, they saw how it evolved, and discovered it was related to the cacao tree. All the other discoveries have been published in the journal Nature Genetics.

    Despite the striking smell, many people actually enjoy eating the fruit. However, not all durian species are edible, and some of them may even cause damage to our health, Even so, the fruit is often imported, significantly contributing to the economy.

同类题4

阅读下文,回答问题

蟋蟀的住宅

    居住在草地上的蟋蟀,差不多和蝉一样有名。它的出名不光由于它的歌唱,还由于它的住宅。

    别的昆虫大多在临时的隐蔽所藏身。它们的隐蔽所得来不费功夫,弃去毫不可惜。蟋蟀和它们不同,不肯随遇而安。它常常慎重地选择住址,一定要排水优良,并且有温和的阳光。它不利用现成的洞穴,它的舒服的住宅是自己一点一点挖掘的,从大厅一直到卧室。

    蟋蝉怎么会有建筑住宅的才能呢?它有特别好的工具吗?没有。蟋蟀并不是挖掘技术的专家。它的工具是那样柔弱,所以人们对它的劳动成果感到惊奇。

    在儿童时代,我到草地上去捉蟋蟀,把它们养在笼子里,用菜叶喂它们。现在为了研究蟋蟀,我又搜索起它们的巢穴来。

    在朝着阳光的堤岸上,青草丛中隐藏着一条倾斜的隧道,即使有骤雨,这里也立刻就会干的。隧道顺着地势弯弯曲曲,最多不过九寸深,一指宽,这便是蟋蟀的住宅。出口的地方总有一丛草半掩着,就像一座门。蟋蟀出来吃周围的嫩草,决不去碰这一丛草。那微斜的门口,经过仔细耙扫,收拾得很平坦。这就是蟋蟀的平台。当四周很安静的时候,蟋蟀就在这平台上弹琴。

    屋子的内部没什么布置,但是墙壁很光滑。

    主人有的是时间,把粗糙的地方修理平整。大体上讲,住所是很简朴的,清洁、干燥、很卫生。假使我们想到蟋蟀用来挖掘的工具是那样简单,这座住宅真可以算是伟大的工程了。

    蟋蟀盖房子大多是在十月,秋天初寒的时候。它用前足扒土,还用钳子搬掉较大的土块。它用强有力的后足踏地,后腿上有两排锯,用它将泥土推到后面,倾斜地铺开。

    工作做得很快。蟋蟀钻到土底下,如果感到疲劳,它就在未完工的家门口休息一会儿,头朝着外面,触须轻微地摆动。不大一会儿,它又进去,用钳子和耙继续工作。我一连看了两个钟头,看得有些不耐烦了。

    住宅的重要部分快完成了。洞已经挖了有两寸深,够宽敞的了。余下的是长时间的整修,今天做一点,明天做一点。这个洞可以随天气的变冷和它身体的增长而加深加阔。即使在冬天,只要气候温和,太阳晒到它住宅的门口,还可以看见蟋蟀从里面不断地抛出泥土来。