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有三个阻值分另为R1=10Ω,R2=20Ω,R3-80Ω的电阻。若实验时需要一个阻值为16Ω的电阻,以下是从这三个电阻中选用两个进行连接,能满足实验要求的是
A.R1和R2并联B.R2和R3并联C.R1和R2串联D.R1和R3串联

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如图所示,根据小磁针静止时的指向画出通电螺线管中的电流方向,电源的正负极及通电螺线管的N、S极

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依照下面的实物图,请画出其电路图:

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在“测量小灯泡电功率”的实验中,已知电源电压为3V,小灯泡的额定电压为2.5V。
(1)连接电路时,开关应________。
(2)请你用笔画线代替导线将图中的电路连接完整。
(3)闭合开关前,应该将滑动变阻器的滑片移动到____端(“A”或“B”端),闭合开关后,发现小灯泡不亮,电流表指针偏转,电压表示数为0,产生故障的原因可能是_____________________________。
(4)排除故障后,实验中测得小灯泡两端的电压为2V时,电流表示数如图所示,则通过小灯泡的电流是________A,此时小灯泡的实际功率为________W。
   

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现在家庭电器化程度越来越高,用电安全是一个十分突出的问题,下表提供了一组部分人的人体电阻平均值数据:
测量项目
完全干燥时
潮湿时
 
电阻
电流(加220V)
电阻
电流(加220V)
手与手之间
200KΩ
1.1×10-3A
5KΩ
 
手与脚之间
300KΩ
7.3×10-4A
8KΩ
 
手与塑料鞋底之间
400KΩ
5.5×10-4A
10KΩ
 
(1)从表中可以看出干燥时电阻大约是潮湿时电阻的_______倍。
(2)在表格中的空格处填入人体潮湿时加220V电压后的电流值;
(3)若对人的安全电流是25mA以下,上述哪几项是十分危险的?
__________________________________________________________
(4)请你谈谈:在生活中,作为中学生安全用电的注意事项(说出一条就行)
__________________________________________________________

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汽车为人类文明作出了巨大贡献,但同时也对自然生态环境造成了污染。为了减少汽车尾气对居民的危害,岳阳市政府购进了一些以天然气为燃料的汽车作为公交车,也改造了大部分出租车以天然气为燃料。请回答以下问题:
(1)这种汽车的发动机在做功冲程中将内能转化为        
 
(2)汽车使用天然气作燃料的优点是(写一条就行)
                                                                       
 

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科目: 来源: 题型:阅读理解

A metaphor is a poetic device that deals with comparison. It compares similar qualities of two dissimilar objects. With a simple metaphor, one object becomes the other: Love is a rose. Although this does not sound like a particularly rich image, a metaphor can communicate so much about a particular image that poets use them more than any other type of figurative language(修辞). The reason for this is that poets compose their poetry to express what they are experiencing emotionally at that moment. Consequently, what the poet imagines love to be may or may not be love we see it. Therefore, the poet’s job is to enable us to experience it, to feel it the same way as the poet does.
Let’s analyze this remarkably unsophisticated metaphor concerning love and the rose to see what it offers. Because the poet uses a comparison with a rose, first we must examine the characteristics of that flower. A rose is spectacular in its beauty; its petals(花瓣) are nicely soft, and its smell is pleasing. It’s possible to say that a rose is actually a feast to the senses of sight, touch, and smell. The rose’s appearance seems to border on(近似于)perfection, each petal seemingly symmetrical(对称的) in form. Isn’t this the way one’s love should be? A loved one should be a delight to one’s senses and seem perfect. However, there is another dimension added to the comparison by using a rose. Roses have thorns(刺). The poet wants to convey the idea that roses can be tricky(机警的). So can love, the metaphor tells us. When one reaches out with absolute trust to touch the object of his or her affection, ouch, a thorn can cause great harm! “Be careful,” the metaphor warns: Love is a feast to the senses, but it can overwhelm us, and it can also hurt us and cause acute suffering. This is the poet’s perception of love--a warning. What is the point? Just this: It took almost 14 sentences to clarify what a simple metaphor communicates in only four words! That is the artistry and the joy of the simple metaphor.
【小题1】According to the passage, what is a metaphor?
A.A comparison between two different objects with similar features.
B.A contrast between two different things to create a vivid image.
C.A description of two similar objects in a poetic way.
D.A literary device specially employed in poetry writing.
【小题2】 The main idea of this passage is that         .
A.rose is a good image in poetryB.love is sweet and pleasing
C.metaphor is ambiguousD.metaphor is great poetic device
【小题3】 It can be inferred from the passage that a metaphor is        .
A.difficult to understandB.rich in meaningC.not precise enoughD.like a flower
【小题4】 As is meant by the author, thorns of a rose_________.
A.protect the rose from harmB.symbolize reduced love
C.add a new element to the image of loveD.represent objects of one’s affection
【小题5】 The meaning of the love-is–a-rose metaphor is that____________-
A.love is a true joyB.true love comes once in a lifetime
C.love does not last long D.love is both good and bad experiences

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电热饮水机有加热和保温两种工作状态(由机内温控开关S0自动控制),从说明书上收集到如下数据及如图所示的电路原理图。
热水箱容量
2L
额定电压
220V
加热时的功率
400W
保温时的功率
40W
 
(1)请分析说明温控开关S0断开时,饮水机处于哪种工作状态?
(2)求电阻R1的阻值;
(3)求电热饮水机在加热状态下的工作电流。

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下列器具中,使用的杠杆属于费力杠杆的是

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汽车、拖拉机的发动机常用水做冷却剂.是因为水具有
A.较小的密度B.较大的比热容
C.较低的凝固点D.较高的沸点

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