实验桌上有如下器材：满足实验要求的电压保持不变的电源一个、电_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题实验题

实验桌上有如下器材：满足实验要求的电压保持不变的电源一个、电阻箱R（电路图符号）一个、已经调节好的电压表和电流表各一只、开关一个、已知阻值的定值电阻R。一个和导线若干．小明想利用实验桌上的器材，设计一个实验证明：“当定值电阻R₀保持不变时，并联电路中总电阻的倒数等于各支路电阻的倒数之和”。请根据上述要求帮助小明画出实验电路图，写出实验步骤并设计实验记录表格．

（1）实验电路图

（2）实验步骤

（3）实验记录表格

答案

（1）实验电路图见下图

（2）实验步骤：

①按电路图将电阻箱R、定值电阻R₀、电流表和电压表接入电路中

②将电阻箱R旋至某一阻值，闭合开关S，用电压表和电流表测量并联电路两端的电压U和通过干路中的电流，将定值电阻R。和电阻箱R的阻值及电压表和电流表的示数记录在表格中；

③仿照步骤②再旋转电阻箱的旋钮5次，使其在电路中接入5个不同的阻值，并用电压表和电流表分别测量对应5次并联电路两端的电压U和通过于路中的电流I，将定值电阻R₀和5次电阻箱R的阻值及对应电压表和电流表的示数记录在表格中；

④根据R= 分别计算出6次并联电路中的总电阻R，并将计算结果记录在表格中

（3）实验记录表格

完形填空

Most people in the world like to enjoy nature. Travel is one of the most popular ways. Nowadays modern transportation can take people everywhere. But people who lived before the 1880s probably would not travel very far. They would not have time to travel far from their work. Anyone who travelled 36 would usually walk or ride a horse. But in Germany a man named Karl Benz had an idea that 37 the world in a dramatic way. In 1885, he made 38 . His car had three wheels, 39 most cars today. The car could only go 40 16 kilometres an hour.
At around the same time, the man 41 his first car in Detroit, America is called Henry Ford. Detroit is now still famous all over the world as the centre of American car-making.
Cars were very few and only 42 people could buy them. 43 , in England cars were thought to be 44 at that time, so for a few years someone 45 walk in front of every car 46 a red flag! This was to make sure that the car did not go too fast and hurt 47 .
In the 1910s, Henry Ford had 48 a better kind of car called the Model T Ford and he built a 49 where the cars could be made 50 . In this way the car could be made 51 and the cost was less and more and more people could 52 them. But there was still a problem 53 all the cars were black. That was because it was 54 to produce cars that were all the same color. Now, of course, you can buy cars in all 55 .

A．a first car

B．the first car

C．his first wheel

D．a first wheel

A．with a speed of

B．at a speed of

C．at speed of

D．for a speed of

D．having made

A．interesting

B．was forced to

A．with machine

B．by machines

D．using hands

选择题

— Whose watch is that?

— Is it _____? [ ]

A. black

B. black watch

C. this watch