问题 探究题

如图所示,电阻R1和R2串联在电路中,现在要计算出R2的阻值,图中所标出的物理量中至少需要知道哪几个量?如何计算?参考表中的示例填写表格(写出两种计算方法)。

需要知道的物理量
计算过程                   
例如U2和IR2=
1
2

答案
需要知道的物理量
    计算过程
1
U、U1和I
R2=
2
U1、U2和R1
R2=R1
3
U、I和R1
R2=-R1
4
U、U1和R1
R2=R1
阅读理解

请阅读下面一篇文章,并按照要求匹配信息。

     Do you know Australia? Australia is the largest island in the world. It is a little smaller than China. It is

in the south of the earth. __1__The population of Australia is nearly as large as that of Shanghai.__2__The cities in Australia have got little air or water pollution. The sky is blue and the water is clean. You can

clearly see fish swimming in the rivers. Plants grow very well.

     Last month we visited Perth, the biggest city in western Australia, and went to a wild flowers' exhibition.__3__We had a wonderful time. Perth is famous for its beautiful wild flowers. In spring every year Perth

has the wild flowers' exhibition.

     After visiting Perth, we spent the day in the countryside. We sat down and had a rest near a path at the foot of a hill. It was quiet and we enjoyed ourselves. Suddenly we heard bells ringing at the top of the hill.

__4__ There were about three hundred sheep coming towards us down the path. __5__After a short

drive from any town, you will find yourself in the middle of white sheep. Sheep, sheep, everywhere are

sheep.

A. The government has made enough laws to fight pollution.

B. Australia is the sixth largest country in the world.

C. Australia is famous for its sheep and kangaroos.

D. Australia is big, but its population is not large.

E. What we saw made us pick up all our things and run back to the car as quickly as we could.

F. There we saw a large number of wild flowers we had never seen before.

G. The people of Australia are very hardworking.

名词解释