在伏安法测电阻实验中，电源电压为6V，待测电阻大约为10Ω，电流表有0.6A、3A两个量程，电压表有3V、15V两个量程。请完成如下问题：（1）本实验中，电流表的量程应选 ，在连接电路前，开关应 ;（2）两图是实验中电流表、电压表的示数，电压表的读数为 V，求得待测电阻的阻值为 Ω。
0.6A 断开 4.5 9
题目分析：（1）电源电压为6V，待测电阻大约为10Ω，根据：
，电流约0.6V，故电流表的量程应选0-0.6A，为了保护电路，及养成良好的连接电路习惯，所有的电学实验，连接电路时，开关都应该断开；
（2）电流表的量程为0-0.6A，所以电流的示数即电流为0.5A，待测电阻大约为10Ω，根据：
，电压为6V左右，故电压表的读数为4.5V，
则：
点评：此题主要考查学生对伏安法测电阻的探究实验，电流表的使用，欧姆定律的应用的理解和掌握，题目难度不大。
| 完形填空 When a rather dirty, poorly dressed person kneels at your feet and puts out his hands to beg __1__a few coins, do you hurry on, not __2__ what to do, or do you feel sad and hurriedly __3__ some money? What should our attitude__4__ beggars be? There can be no question that the world is full of terribly sad stories. It __5__ be terrible to have no idea where our next meal is going to come from. It seems __6__ not to give some money to beggars. __7__, most of the world's great religions order us to be open-hearted and __8__what we have with those less lucky than ourselves. But has the world changed? Maybe what was morally right in the old days, __9__ one knew exactly who in the village had suffered misfortune and needed help, is no longer the best idea. Quite a few people will not give to beggars. Let us look at their __10__. First, some believe that many city beggars dress up __11__ to look pitiable and actually make a good __12__ from begging. Giving to beggars only encourages this sort of evil. __13__, there is the worry that the money you give will be spent on beer, wine or drugs. Thirdly, there is the opinion__14__there is no real excuse for begging. One might be poor, but that is no reason for losing one's sense of __15__ and self-dependence. Related to this is the opinion that the problem should be handled by the government __16__ordinary people. Some people think beggars should go to the local government department and __17__ help. It is hard to come to any final conclusion: there are various __18__and we must __19__ them differently. A few coins can save a life in some situations, and even if the money is wasted, that does not take away the moral goodness of the__20__. | ||||
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