问题 问答题

(I)(1)如图甲所示,在“描绘小灯泡的伏安特性曲线”实验中,同组同学已经完成部分导线的连接,请你在实物接线图中完成余下导线的连接.

(2)某同学从标称为“220V  25W”“220V  300W”“220V  500W”的3只灯泡中任选一只,正确使用多用电表测量灯泡阻值如图乙所示.该灯泡的阻值是______Ω,标称的额定功率为______W.

(II)(1)在“探究单摆周期与摆长的关系”实验中,两位同学用游标卡尺测量小球的直径如图甲、乙所示.测量方法正确的是______(选填“甲”或“乙”).

(2)实验时,若摆球在垂直纸面的平面内摆动,为了将人工记录振动次数改为自动记录振动次数,在摆球运动最低点的左、右两侧分别放置一激光光源与光敏电阻,如图甲所示.光敏电阻与某一自动记录相连,该仪器显示的光敏电阻阻值R随时间t变化图线如图乙所示,则该单摆的振动周期为______.若保持悬点到小球顶点的绳长不变,改用直径是原小球直径2倍的另一小球进行实验,则该单摆的周期将______(填“变大”、“不变”或“变小”),图乙中的△t将______(填“变大”、“不变”或“变小”).

答案

(I)(1)由题意可知,应采用分压接法,因灯泡内阻较小,故应采用电流表外接法; 故答案如下图所示:

(2)欧姆表的指示值为16,所选倍率为×10,因此读数为R=16×10=160Ω,由于灯泡正常工作时的电阻为:R=

U2
P
,比不工作时的电阻大的多,而“220 V  25 W”、“220 V  300 W”、“220V  500W”正常工作时的电阻分别为1936Ω、161Ω和98Ω.故为25W.

故答案为:160,25

(II)(1)用游标卡尺测量小球的直径,应将小球卡在外爪的刀口上.故乙正确.

故答案为:乙.

(2)单摆在一个周期内两次经过平衡位置,每次经过平衡位置,单摆会挡住细激光束,从R-t图线可知周期为2t0.摆长等于摆线的长度加上小球的半径,根据单摆的周期公式单摆公式T=2π

l
g
摆长变大,所以周期变大.

故答案为:2t0,变大,变大.

写句子
单项选择题

The amazing success of humans as a (91) is the result of the evolutionary development of our brains which has led, among other things, to tool-using, tool-making, the (92) to solve problems by logical reasoning, thoughtful cooperation, and language. One of the most striking ways in which chimpanzees biologically (93) humans (94) in structure of their brains. The chimpanzee, with the capacity for (95) reasoning, (96) a type of intelligence more like that of humans than (97) any other mammal living today. The brain of the modern chimpanzee is probably not too dissimilar (98) the brain that so many millions of years ago (99) the behavior of the first ape man.
For a long time, the fact that prehistoric people made (100) was considered to be one of the major (101) distinguishing them from other creatures. (102) pointed out earlier, I have watched chimpanzees (103) grass stems in order to use them to probe for termites. It is tree that the chimpanzee does not (104) tools to "a regular and set pattern"—but then, (105) people, before their development of stone tools, undoubtedly poked around (106) sticks, and straws, at which stage it seems (107) , that they made tools to a set pattern either.
It is because of the close (108) in most people’s minds of tools with humans (109) special attention has always been focused upon any animal able to use an object as a tool: but it is important to realize that this ability, on its own, does not necessarily indicate any special intelligence in the creature (110) .

A.As

B.Since

C.If

D.When