题目

What is a library for? Most libraries have books and other things to read. Many of them  have things to listen to. Some libraries even have computers. Very few people would think of a library as a place to live in.One library in New York City turned into(变成)a home for 250 people for a f ew days.These were all people near the library. They slept on the floor. Why did the people move into the library?The people moved into the library because the city wanted to close it to save money. These 250 New Yorkers loved their library. They didn't want to lose it. So they moved in. They knew that the小明同学要用“伏安法”测量标有“2.5V”字样的小灯泡的电阻，连接了如图所示的电路．（1）请你用笔画线代替导线完成电路连接．（2）闭合开关S之前，应将滑动变阻器的滑片滑______端（填“左”或“右”）．（3）检查电路连接无误后，小明开始实验．通过实验，他记录了三组实验数据如下表．请你帮他将表中空白格内的数值补上．实验次数123电压/V1.52.02.5电流/A0.250.270.3电阻/Ω67.4灯泡亮度暗较亮亮（4）小明知道，在一般情况下都认为灯丝电阻是不变的．但他从上表中的数据发现：三次测得的灯丝电阻相差较大．请你帮他说明原因．______．