某同学利用电压表和电流表测量电阻Rx的阻值，所用的电源由两节新干电池组成，选用的滑动变阻器上标有

\u67d0\u540c\u5b66\u5229\u7528\u7535\u538b\u8868\u548c\u7535\u6d41\u8868\u6d4b\u91cf\u7535\u963bRx\u7684\u963b\u503c\uff0c\u6240\u7528\u7684\u7535\u6e90\u7531\u4e24\u8282\u65b0\u5e72\u7535\u6c60\u7ec4\u6210\uff0c\u9009\u7528\u7684\u6ed1\u52a8\u53d8\u963b\u5668\u4e0a\u6807\u6709\u201c20

\uff081\uff09\u7535\u538b\u8868\u65e0\u793a\u6570\uff0c\u5219\u8bf4\u660e\u7535\u963bRx\u4e24\u7aef\u65e0\u7535\u538b\uff0c\u5219\u53ef\u80fd\u662f\u7535\u963bRx\u77ed\u8def\u6216\u6ed1\u52a8\u53d8\u963b\u5668\u65ad\u8def\uff1b\uff082\uff09\u82e5\u539f\u56e0\u662fRx\u77ed\u8def\uff0c\u5219\u63a5\u5165\u5bfc\u7ebf\u540e\uff0c\u60c5\u51b5\u4e0d\u53d8\uff0c\u7535\u538b\u8868\u793a\u6570\u4ecd\u4e3a\u96f6\uff0c\u7535\u6d41\u8868\u6709\u793a\u6570\uff1b\u82e5\u539f\u56e0\u662f\u6ed1\u52a8\u53d8\u963b\u5668\u65ad\u8def\uff0c\u5219\u63a5\u5165\u5bfc\u7ebf\u540e\uff0c\u60c5\u51b5\u4e0d\u53d8\uff0c\u7535\u8def\u4e2d\u4ecd\u65e0\u7535\u6d41\uff0c\u7535\u6d41\u8868\u793a\u6570\u4e3a\u96f6\uff0c\u7535\u538b\u8868\u793a\u6570\u4e5f\u4e3a\u96f6\uff1b\uff083\uff09\uff08a\uff09\u7531\u9898\u610f\u77e5\uff0c\u7535\u538b\u8868\u7684\u91cf\u7a0b\u4e3a0\uff5e3V\uff0c\u5206\u5ea6\u503c\u4e3a0.1V\uff0c\u793a\u6570\u4e3a1V\uff1b\u7535\u6d41\u8868\u7684\u91cf\u7a0b\u4e3a0\uff5e0.6A\uff0c\u5206\u5ea6\u503c\u4e3a0.02A\uff0c\u793a\u6570\u4e3a0.1A\uff0c\u5219Rx=UI=1V0.1A=10\u03a9\uff1b\uff08b\uff09\u5b9e\u9a8c\u4e2d\u53ea\u6d4b\u91cf\u4e86\u4e00\u7ec4\u6570\u636e\uff0c\u6ca1\u6709\u591a\u6b21\u6d4b\u91cf\u6c42\u5e73\u5747\u503c\uff0c\u6240\u4ee5\u5b9e\u9a8c\u8bef\u5dee\u8f83\u5927\uff0c\u5b9e\u9a8c\u7ed3\u679c\u4e0d\u5408\u7406\uff0e\u6545\u7b54\u6848\u4e3a\uff1a\uff081\uff09R\u65ad\u8def\uff08\u6216Rx\u77ed\u8def\uff09\uff1b\uff082\uff09\u7535\u538b\u8868\u65e0\u793a\u6570\uff0c\u7535\u6d41\u8868\u65e0\u793a\u6570\uff08\u6216\u7535\u538b\u8868\u65e0\u793a\u6570\uff0c\u7535\u6d41\u8868\u6709\u793a\u6570\uff09\uff1b\uff083\uff09\uff08a\uff0910\uff1b\uff08b\uff09\u4e0d\u5408\u7406\uff0c\u6ca1\u6709\u591a\u6b21\u6d4b\u91cf\u53d6\u5e73\u5747\u503c\uff0e

\u6839\u636e\u5b9e\u7269\u56fe\u53ef\u77e5\uff0c\u7535\u538b\u8868\u6d4b\u91cf\u5b9a\u503c\u7535\u963b\u548c\u6ed1\u52a8\u53d8\u963b\u5668\u4e24\u7aef\u7684\u603b\u7535\u538b\uff0c\u56e0\u6b64\u7535\u538b\u8868\u7684\u6b63\u63a5\u7ebf\u67f1\u4e0e\u6ed1\u52a8\u53d8\u963b\u5668\u7684\u76f8\u8fde\u7684\u5bfc\u7ebf\u6539\u63a5\u5230\u88ab\u6d4b\u7535\u963b\u7684\u53f3\u63a5\u7ebf\u67f1\uff0c\u6b63\u786e\u8fde\u63a5\u65b9\u6cd5\u5982\u4e0b\uff1a

你考虑到的这一点不无道理，按照你的想法，答案应是Rx断路或R断路。但对于这道题来说，题目明确地说了电路中只有一处出现故障，所以你的答案显然不符合题意。我觉得这道题答案应该是R断路，我想出题人本意也是R断路，只是出这道题的时候逻辑性不够严密。可以反过来想，如果Rx断路，他为什么不说电压表的示数始终为零！

(via  菁优网)

（1）“略”（2）断开 a （3）4.5 （4）“略” （5） 12.3 “略” （6）定值电阻断路 （7）变阻器阻值无法再调大。

没有图……

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