问题 填空题

如图甲所示电流表A1的示数为0.5A,电流表A2的示数如图乙所示为       ,则通过灯泡Ll的电流为         

 

答案

0.36     0.14

考查知识点:电流表的读数方法;并联电路的电流规律.

思路分析:从电路中可以看出,两灯泡并联,电流表A1测量干路的电流I=0.5A,电流表A2测量通过支路L2的电流I2.根据图示情况可以判断电流表A2的量程是0~0.6A.通过观察指针所指位置可知, A2的示数为0.36A.

则L1的电流是I1=0.5A-0.36A=0.14A.

具体解答过程:解:由图可知:灯L1与灯L2并联,电流表A1测量干路的电流I=0.5A,电流表A2测量通过支路L2的电流I2

根据并联电路电流规律可知:干路电流大于支路电流.由图可知电流表A2的量程为0-0.6A,0.6A量程的分度值是0.02A,所以A2的读数是0.36A.

根据并联电路电流规律:I=I1+I2

得出灯L1的电流:I1=I-I2=0.5A-0.36A=0.14A.

故答案为 0.36   0.14.

试题点评:(1)做这类题时,要先分析电路图,然后利用电路的规律分析计算.

(2)掌握电流表和电压表的读数.

(3)掌握串联电路和并联电路的电流、电压、电阻的特点.

阅读理解

Fire can help people in many ways. But it can also be very harmful. Fire can make water hot and house warm, give light and cook food. But fire can burn (燃烧) things, too. It can make trees, houses, animals and other things catch fire (起火). If some people can't run away from fire, it can kill them. This happens in every country every year.

Sometimes big fire can burn forests. A month ago, a large forest fire broke out in Yunnan Province. It lasted nearly half a month. The forest in Heilongjiang Province and the grassland in Inner Mongolia caught fire in May, 2006. After more than ten days' fight, over 30,000 people and soldiers put out (扑灭) the fire at last.

Nobody knows clearly when people began to make fire, but there are many interesting stories about the first time a man or a woman started a fire. One story from Australia tells about a man who went to the sun and brought fire down a long time ago. Today people know how to make a fire with matches (火柴). Children sometimes like to play with them. But matches can be very dangerous. The match can burn a piece of paper and then it can burn a house. A small fire can become a big fire, and destroy many things. Fire kills many people every year. So you must be careful with fire.

小题1:The main idea of the passage is that _________.

A.fire is dangerous and harmful

B.forest fire can be easily put out

C.who started a fire the first time

D.every month there is a forest fire in Yunnan Province小题2:Matches can be dangerous because _________.

A.they always burn a house

B.they can make things catch fire

C.they can burn a piece of paper

D.they kill many animals every year小题3:The word “destroy” in the passage means ________in Chinese.

A.破灭

B.炸毁

C.毁灭

D.粉碎小题4:The writer of the passage wants to tell us that ________.

A.we know when man began to make a fire

B.people should use fire carefully

C.fire can burn down all things in the world

D.all children like to play with matches

多项选择题