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问题 实验题

在交流电路中，如果电源电动势的最大值不变，频率可以改变，在右图所示电路的a、b两点间依次将图中的电路元件（1）（2）（3）单独接入，当使交变电流频率增加时，可以观察到A1读数__________________，A2读数__________________，A3读数_______________.（以上各空填“不变”“增大”或“减小”）

答案

增大 不变 减小

接入（1）时，电容对交变电流有阻碍作用，而容抗随交流电的频率增加而减小，故A1读数增大；接入（2）时，电阻对交变电流有阻碍作用，且电阻的大小与交变电流的频率无关，故交变电流的频率增加时，A2读数不变；接入（3）时，电感对交变电流有阻碍作用，感抗随交变电流频率的增加而增大，故当交变电流的频率增加时，A3的读数减小.

选择题

生态城市建设让人与自然更趋和谐。目前苏州正在创建国家生态城市，为了进一步加强城市生态环境建设，以下措施不合理的是                                （         ）

A．要做到生态良性循环

B．要做到经济、环境与社会的和谐进步

C．要进一步做好城市绿化工作

D．可先加快工业化进程以促进经济发展，到一定阶段再保护环境
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单项选择题

There is virtually no limit to how one can serve community interests, from spending a few hours a week with some charitable organization to practically full-time work for a social agency. Just as there are opportunities for voluntary service (1) (VSO) for young people before they take up full-time employment, (2) there are opportunities for overseas service for (3) technicians in developing countries. Some people, (4) those who retire early, (5) their technical and business skills in countries (6) there is a special need.

So in considering voluntary or (7) community service, there are more opportunities than there (8) were when one first began work. Most voluntary organizations have only a small full-time

(9) and depend very much on volunteers and part-timers. This means that working relationships are different from those in commercial organizations, and values may be different. (10) some ways they may seem more casual and less efficient, but one should not (11) them by commercial criteria. The people who work with them do so for different reasons and with different (12) , both personal and (13) . One should not join them (14) to arm them with professional experience; they must be joined with commitment to the (15) , not business efficiency. Because salaries are (16) or non-existent many voluntary bodies offer modest expense. But many retired people take part in community service for (17) , simply because they enjoy the work.

Many community activities possible (18) retirement were also possible during one’s working life but they are to be undertaken (19) seriously for that. Retired people who are just looking for something different or unusual to do should not consider (20) community service.

4（）

A.partially

B.partly

C.particularly

D.passionately
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