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测定“金属丝的电阻率”实验中，待测金属丝电阻约为5Ω．要求测量结果尽量准确，提供以下器材供选择：

A．电池组（3V，内阻约1Ω）                      B．电流表（0-0.6A，内阻约0.125Ω）

C．电压表（0-3V，内阻4KΩ）                     D．电压表（0-15V，内阻15KΩ）

E．滑动变阻器（0-2000Ω，允许最大电流0.3A）

F．滑动变阻器（0-20Ω，允许最大电流1A）         G．开关、导线若干

（1）实验不选择的器材有______（填写仪器前字母代号）；伏安法测电阻时，A应该______（填：内接或外接）

（2）用螺旋测微器测得金属丝直径d的读数如图，则读数为_______mm

（3）若用L表示金属丝长度，d表示直径，测得电阻R．则金属丝电阻率的表达式ρ=______．

答案

（1）因金属丝电阻值为2Ω，由闭合电路欧姆定律得最大电阻

R m
=
E
1
3
I
=
3
0.2
=15Ω，所以滑动变阻器E的阻值太大，故不选择E，又电源电动势为3V，所以不能选择D．因金属丝电阻远小于电压表内阻，电流表应用外接法接法．

（2）螺旋测微器读数为d=1.5mm+49.8×0.01mm=1.998mm，（1.996-1.999均可）

（3）由R=

ρL
S
，及S=
1
4
πd2 
得ρ=
πd2 
R
4

故答案为（1）DE，（2）外

         （2）1.998（1.996-1.999）

         （3）

πd2 
R
4

完形填空

阅读下面短文并回答问题，然后将答案写到答案卡相应的位置上（请注意每题的词数要求）。

Jack London was born in San Francisco in 1876．He was abandoned by his father，“Professor” William Henry Chaney，a fortune telling person，and raised in Oakland by his mother Flora Wellman，a music teacher．London’s stepfather，John London，whose surname he took，was a failed storekeeper. London’ youth marked by poverty. At the age of the he became a crazy reader, and borrowed books from the Oakland Public Library, where Ina Coolbirth told him to read the works of Flaubert, Tolstoy and other major novelists.

After leaving school at the age of 14，London worked as a seaman，rode in trains as a wanderer and adopted socialistic views as a member of the protest armies of the unemployed．In 1894 he was arrested in Niagara Fails and put into prison for wandering．These years made him determined to raise himself out of poverty but they also gave later materials for such works as The Sea Wolf（1 904），which partly came from his horrible experiences as a sailor in the Pacific Ocean．

Without having much formal education，London spent much time in public libraries reading fiction，philosophy，poetry，political science，and at the age of 19 got admittance to the University of California in Berkeley．During this period he had already started to write．London left the school before the year was over and went to seek his fortune in the Klondike gold rush of 1 89 7．His attempt was unsuccessful．London spent the winter near Dawson City，suffering from illness．In the spring he returned to San Francisco with his notebook full of plans for stories．For the remainder of 1 89 8 London again tried to earn his living by writing．London’s first novel，The Son of the Wolf，appeared’in 1900．By 1904 Jack London was the author of 10 books．The Son of the Wolf got a wide audience as did his other Alaska stories，The Call of the Wild（1903），White Fang（1906），and Burning Daylight（1910）．Jack London died on November 22，1916．

小题1:What did Ina Coolbirth tell London in the Oakland Public Library?（Within 15 words）

小题2:Why were London's horrible experiences as a sailor good for him?（Within 12 words）

小题3:What was wrong with London near Dawson City?（Within 5 words）

小题4:What is London’s first novel?（Within 5 words）

小题5:How is the text developed?（Within 5 words）
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已知苯甲醛与乙酸酐[(CH3CO)2O]在一定条件下可以通过Perkin反应生成肉桂酸，方程式（已配平）如下：

苯甲醛                    肉桂酸

（1）1mol苯甲醛与足量银氨溶液在水浴条件下反应最多能生成        mol银单质；写出肉桂酸完全加氢后产物的分子式             。

（2）上述反应中的产物M能与碳酸氢钠反应并放出气体，则M的结构简式是           。

（3）溴苯（C6H5Br）与丙烯酸乙酯（CH2＝CHCOOC2H5）在氯化钯催化下可直接合成肉桂酸乙酯，该反应属于Beck反应，其反应方程式为                                  

（不要求标出反应条件），该反应类型属于              。

已知：在药物、香料合成中常利用醛和醇反应生成缩醛来保护醛基，此类反应在酸催化下进行。例如：

（4）已知具有五元环和六元环结构的缩醛比较稳定。写出用乙二醇（HOCH2CH2OH）保护苯甲醛中醛基生成的缩醛B（分子式：C9H10O2）的结构简式                。

（5）缩醛B（分子式：C9H10O2）符合以下条件的同分异构体有两种，写出它们的结构简式                 。

①苯环上只有一个取代基；②能发生水解反应和银镜反应。
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