（7分）小明和小华同学为了探究“电流通过导体产生的热量与电阻

问题实验题

（7分）小明和小华同学为了探究“电流通过导体产生的热量与电阻的关系”，设计了如图所示的实验电路。两个烧瓶A、B中盛有质量、初温相等的煤油，R_A与R_B是阻值不同的电热丝。

（1）R_A与R_B采用串联的连接方式，其目的是为了控制通电时间、相等。

（2）小明同学为比较R_A与R_B阻值的大小，用电压表分别测出R_A与R_B两端电压大小，发现U_A<U_B，则R_A R_B（选填“>”、“<”或“=”）。

（3）在相同时间内，可通过观察来比较电流通过电热丝产生的热量多少；为了升温较快，实验液体选用煤油而不选用水，主要是水的比热容比煤油。

（4）小华想改装实验装置用来“测量煤油的比热容大小”，则他们应将烧瓶A中煤油换成与其（选填“质量”或“体积”）相等的水，并将电热丝R_A换成的电热丝。测量时，水和煤油的初温均为t₀，通电一段时间后，水和煤油的末温分别为t_水、t_煤油，请写出煤油比热容的表达式：c_煤油= 。（已知水的比热容为c_水）

答案

（1）通过R_A与R_B的电流（2）< （3）温度计上升的示数快慢（或温度计变化的示数多少）大（4）质量与R_B阻值相等、c_水（t_水-t₀）/（t_煤油-t₀）

题目分析：（1）串联电路电流相等，要研究电流通过导体产生的热量与电阻的关系，控制电流相等使用串联电路来控制电流相等。

（2）在串联电路中电压的分配和电阻成正比，用电压表分别测出R_A与R_B两端电压大小，发现U_A<U_B说明电阻R_A<R_B。

（3）在相同时间内，可通过观察温度计变化的示数多少，来比较电流通过电热丝产生的热量多少；为了升温较快，实验液体选用煤油而不选用水，主要是水的比热容比煤油大。

（4）小华想改装实验装置用来“测量煤油的比热容大小”，要控制产生热量的多少相同，就得使电阻相同，水和煤油的质量相等。根据水的比热容已知，求出煤油的比热容。

完形填空。
Traditional Chinese doctors believe we need a balance of yin and yang to __1__. For example, are you often weak and tired? Maybe you have __2__ yin. You should eat hot yang foods, like beef. Eating Dangshen and Huangqi herbs __3__ also good __4__ this. But people who are too __5__ and angry may have too much yang. Chinese doctors believe that they should eat __6__ yin foods like tofu. Chinese medicine is now popular in many __7__. It's easy __8__ a healthy lifestyle, and it's __9__ to eat a balanced diet. As for me, I exercise every day, usually when I come home from school. My __10__ habits are pretty good, I try to eat a lot of vegetables. I eat fruit and drink milk every day. I never drink __11__. Of course, I love junk food too, but I try to eat it only __12__. Oh, and I sleep __13__. So you see, I look after my health. And my healthy lifestyle __14__. Good food and __15__ help me to study better.
( )1. A. be health ( )2. A. too many ( )3. A. be ( )4. A. for ( )5. A. q uiet ( )6. A. little ( )7. A. places ( )8. A. have ( )9. A. difficult ( )10. A. eating ( )11. A. orange juice ( )12. A. one time a week ( )13. A. nine hour every night ( )14. A. help me get good grades ( )15. A. exercise	B. be healthy B. too much B. is B. at B. outgoing B. much B. cities B. to have B. important B. to eat B. coffee B. once a week B. nine hours every night B. helps me get good grades B. exercises	C. in healthy C. many too C. am C. with C. active C. more C. western countrie C. having C. easy C. eat C. apple juice C. one time for a week C. nine hours every nights C. help me to get good grades C. exercising	D. in health D. much too D. are D. in D. stressed out D. less D. towns D. has D. interesting D. eating D. hot water D. once for a week D. nine hour every night D. helps me getting good grades D. to exercise