问题 填空题

图1为某热敏电阻(电阻值随温度的改变而改变,且对温度很敏感)的I-U关系曲线图.

(1)为了通过测量得到图1所示,I-U关系的完整曲线,在图2、图3两个电路中应选择图______;简要说明理由:______.

(2)在图4电路中,电源电动势为9V,内阻不计,理想电流表读数为70mA,定值电阻R1=250Ω.由热敏电阻的,I-U关系曲线可知,热敏电阻两端的电压为______V;电阻R2的阻值为______Ω.

答案

(1)由题意可知,本实验要求能得出完整的I-U图象,故应采用分压接法,故选2;原因是:图2电路电压可从0V调到所需电压,调节范围较大.而图3电路不能测得0V附近的数据.

(2)由欧姆定律可知,流过R1的电流为:

9
250
=36mA;则流过热敏电阻的电流为70-36=34mA;由图可知,热敏电阻两端的电压为5.2V;

则定值电阻两端的电压为9-5.2V=3.8V;则R2的阻值为:R2=

3.8V
0.034A
=111.8Ω;

故答案为;(1)2;图2电路电压可从0V调到所需电压,调节范围较大.(2)5.2;111.8

阅读理解

Good afternoon, everyone! This is Rose Garden Middle School Radio. John Smith speaking, with something new to share with you today. We all know that thinking green is sometimes the most difficult thing to do, but not impossible! Bed ZED, a new eco-friendly village (生态村) in the south of London, has done a great job of providing its villagers with a high level living while getting them to pay more attention to protecting the environment.

people in Bed ZED have done many things. They recycle their paper, plastic, glass and other daily things. They build many houses whose windows face south in order to get as much sunlight as possible. The rainwater is collected for use in the toilets. Also, the people there travel to work in shared cars or use public transportation if they work far away.

Now, you may think it’s not easy to live such a life, but let me tell you. it’s not! It’s a way of life. We just have to say no to what is bad for the environment, and begin working on ideas to protect it. Life would be much more pleasant if villages like Bed ZED existed (存在) all over the world!

Thank you for listening!

小题1: What people in Bed ZED often do is__________

A. to build a lot of houses         B. to go to work in their own cars

C. to recycle the paper, plastic and glass

小题2:In Bed ZED, the water used in the toilet may come from ____________.        

A. river water     B. running water           C. collected rainwater

小题3:People in Bed ZED usually go to work _________if they work far away.

A. by bus               B. on foot               C. by bike

小题4:The expression "thinking green" might mean the same as__________ .

A. building a green house  

B. keeping simple thoughts 

C. protecting the environment

小题5:The writer’s opinion is that________________ .

A. people should be against building eco-friendly villages

B. Bed ZED is a good example in protecting the environment!

C. the idea of thinking green is hard to work on

单项选择题