某同学在实验室要测定一未知电阻Rx的阻值(1)他首先用多用电表粗略测定该电阻阻值,步骤如下,请你按题
\u67d0\u540c\u5b66\u5728\u5b9e\u9a8c\u5ba4\u8981\u6d4b\u5b9a\u4e00\u672a\u77e5\u7535\u963bR x \u7684\u963b\u503c\u3002\uff081\uff09\u4ed6\u9996\u5148\u7528\u591a\u7528\u7535\u8868\u7c97\u7565\u6d4b\u5b9a\u8be5\u7535\u963b\u963b\u503c\uff0c\u6b65\u9aa4\u5982\u4e0b\uff0c\u8bf7\u4f60\uff081\uff09\u2461\u5c06\u7ea2\u9ed1\u4e24\u8868\u7b14\u77ed\u63a5\uff0c\u6b27\u59c6\u8c03\u96f6\uff0c\u53f3\uff0c\u24627000\uff0c\uff082\uff09B \u8bd5\u9898\u5206\u6790\uff1a\uff081\uff09\u6b27\u59c6\u8868\u8c03\u96f6\u7684\u8fc7\u7a0b\u4e3a\uff1a\u5c06\u7ea2\u9ed1\u4e24\u8868\u7b14\u77ed\u63a5\uff0c\u8c03\u8282\u6b27\u59c6\u8c03\u96f6\u65cb\u94ae\uff0c\u4f7f\u7535\u6d41\u8868\u7684\u6307\u9488\u8fbe\u5230\u6ee1\u523b\u5ea6\uff0c\u5373\u523b\u5ea6\u76d8\u53f3\u4fa7\u201c0\u201d\u523b\u7ebf\u5904\uff1b\u6b27\u59c6\u8868\u7684\u8bfb\u6570\u4e3a7.0\u03a9\uff0c\u5728\u4e58\u4ee5\u500d\u73871k\uff0c\u6545\u6b27\u59c6\u8868\u7684\u8bfb\u6570\u4e3a7000\u03a9\uff1b\uff082\uff09\u8981\u66f4\u7cbe\u786e\u5730\u6d4b\u51fa\u8be5\u7535\u963b\u7684\u963b\u503c\uff0c\u5219\u9700\u8981\u591a\u6d4b\u51e0\u7ec4\u6570\u636e\uff0c\u6545\u9009\u62e9\u5206\u538b\u7535\u8def\uff0c\u53c8\u7531\u4e8eR x =7000\u03a9\uff0c\u5c5e\u4e8e\u5927\u7535\u963b\uff0c\u7528\u5b89\u57f9\u8868\u7684\u5185\u63a5\u6cd5\uff0c\u6545\u9009\u62e9B\u7535\u8def\u3002
\u5f53S1\u3001S2\u90fd\u95ed\u5408\u65f6\uff0cRx\u88abS1\u77ed\u8def\uff0c\u7531\u4e8e\u6b64\u65f6\u7535\u8def\u4e2d\u53ea\u6709\u6ed1\u52a8\u53d8\u963b\u5668\uff0c\u90a3\u4e48\u5b83\u4e24\u7aef\u7684\u7535\u538b\u5c31\u7b49\u4e8e\u7535\u6e90\u7535\u538b\uff0c\u8fd9\u4e00\u6b65\u5c31\u7b49\u4e8e\u6d4b\u51fa\u4e86\u7535\u6e90\u7535\u538b\u4e3aU1
\u7136\u540e\u987a\u4fbf\u7b97\u51fa\u6ed1\u52a8\u53d8\u963b\u5668\u6b64\u65f6\u7684\u963b\u503cR\u6ed1=U1/I1\u3002\u56e0\u4e3a\u4e0b\u4e00\u6b65\u4fdd\u6301\u6ed1\u52a8\u53d8\u963b\u5668\u63a5\u5165\u7535\u8def\u4e2d\u7684\u7535\u963b\u503c\u4e0d\u53d8\uff0c\u6240\u4ee5\u7b97\u51fa\u7559\u4e0b\u4e00\u6b65\u5f85\u7528\u3002
\u5f53\u65ad\u5f00S2\u65f6\uff0c\u6ed1\u52a8\u53d8\u963b\u5668\u548cRx\u4e32\u8054\uff0c\u6b64\u65f6\u7535\u538b\u8868\u6d4b\u7684\u662f\u6ed1\u52a8\u53d8\u963b\u5668\u4e24\u7aef\u7684\u5206\u538b\u3002\u5927\u5c0f\u4e3aU2\uff0c\u7531\u4e8e\u7535\u6e90\u7535\u538b\u6052\u5b9a\uff0c\u4ecd\u4e3aU1\uff0c\u53ef\u63a8\u51faRx\u4e24\u7aef\u7535\u538b\u4e3aU1-U2
\u73b0\u5728\u4e07\u4e8b\u5177\u5907\u4e86\uff0c\u7528\u4e00\u4e0b\u4e32\u8054\u7535\u8def\u7684\u5206\u538b\u516c\u5f0f\uff1aU1/U2=R1/R2\u5c31\u884c\u4e86
\u4ee3\u4eba\u6570\u636e\u5f97\uff1a(U1-U2)/U2=Rx/R\u6ed1 \u6ce8\u610f\u5176\u4e2dR\u6ed1=U1/I1\u5df2\u5728\u4e0a\u9762\u7b97\u51fa
\u89e3Rx=\u3014(U1-U2)/U2\u3015\u00d7\uff08U1/I1\uff09
\u89e3\u7b54\u5b8c\u6bd5
所测电阻值为:7×1K=7000Ω;
(2)为更精确的测出电阻的阻值,滑动变阻器采用分压接法,被测电阻阻值较大,故采用电流表内接,所以电路图选:B;
(3)从电源的正极出发,依次连接如图.
故答案为:(1)红黑两表笔短接,欧姆调零,右,7000,(2)B.(3)如图.
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