在并联电路中,为什么总电阻比各支路的电阻小?
\u5e76\u8054\u7535\u8def\u4e2d\u603b\u7535\u963b\u548c\u5404\u652f\u8def\u7684\u7535\u963b\u6709\u4ec0\u4e48\u5173\u7cfb?\u603b\u7535\u963b\u5c0f\u4e8e\u5404\u652f\u8def\u7684\u7535\u963b\uff0c\u5e76\u8054\u7535\u8def\u4e2d\uff1a1/R\u603b=1/R1+1/R2+1/R3+\u2026\u20261/RN\u3002
\u5e76\u8054\u662f\u5143\u4ef6\u4e4b\u95f4\u7684\u4e00\u79cd\u8fde\u63a5\u65b9\u5f0f\uff0c\u5176\u7279\u70b9\u662f\u5c062\u4e2a\u540c\u7c7b\u6216\u4e0d\u540c\u7c7b\u7684\u5143\u4ef6\u3001\u5668\u4ef6\u7b49\u9996\u9996\u76f8\u63a5\uff0c\u540c\u65f6\u5c3e\u5c3e\u4ea6\u76f8\u8fde\u7684\u4e00\u79cd\u8fde\u63a5\u65b9\u5f0f\u3002\u901a\u5e38\u662f\u7528\u6765\u6307\u7535\u8def\u4e2d\u7535\u5b50\u5143\u4ef6\u7684\u8fde\u63a5\u65b9\u5f0f\uff0c\u5373\u5e76\u8054\u7535\u8def\u3002
\u6269\u5c55\u8d44\u6599
\u5e76\u8054\u7535\u8def\u7684\u7279\u70b9:
1\u3001\u5e76\u8054\u7535\u8def\u4e2d\u5404\u652f\u8def\u7684\u7535\u538b\u90fd\u76f8\u7b49\uff0c\u5e76\u4e14\u7b49\u4e8e\u7535\u6e90\u7535\u538b\uff1aU=U1=U2
2\u3001\u5e76\u8054\u7535\u8def\u4e2d\u7684\u5e72\u8def\u7535\u6d41(\u6216\u8bf4\u603b\u7535\u6d41)\u7b49\u4e8e\u5404\u652f\u8def\u7535\u6d41\u4e4b\u548c\uff1aI=I1+I2
3\u3001\u5e76\u8054\u7535\u8def\u4e2d\u7684\u603b\u7535\u963b\u7684\u5012\u6570\u7b49\u4e8e\u5404\u652f\u8def\u7535\u963b\u7684\u5012\u6570\u548c\uff1a1/R=1/R1+1/R2\u6216\u5199\u4e3a\uff1aR=(R1+R2)/R1xR2
4\u3001\u5e76\u8054\u7535\u8def\u4e2d\u7684\u5404\u652f\u8def\u7535\u6d41\u4e4b\u6bd4\u7b49\u4e8e\u5404\u652f\u8def\u7535\u963b\u7684\u53cd\u6bd4\uff1aI1/I2=R2/R1
5\u3001\u5e76\u8054\u7535\u8def\u4e2d\u5404\u652f\u8def\u7684\u529f\u7387\u4e4b\u6bd4\u7b49\u4e8e\u5404\u652f\u8def\u7535\u963b\u7684\u53cd\u6bd4\uff1aP1/P2=R2/R1
\u9664\u6b64\u5916\uff0c\u57fa\u672c\u516c\u5f0f\u6709\u6b27\u59c6\u5b9a\u5f8b\uff1aI=U/R
\u5e76\u8054\u7535\u8def\u4e2d\uff0c\u4efb\u4f55\u4e00\u4e2a\u5206\u7535\u963b\u90fd\u5927\u4e8e\u603b\u7535\u963b
\u7406\u7531\u5982\u4e0b\uff1a
\u7531\u4e8e\u5e76\u8054\u7535\u8def\u4e2d\uff0c\u7535\u538b\u4e00\u5b9a\uff0c\u5404\u5206\u7535\u6d41\u4e4b\u548c\u7b49\u4e8e\u603b\u7535\u6d41\uff0c\u636eI=U/R\u53d8\u5f62\u4e3aR=U/I R\u603b=U\u603b/I\u603b
R1=U\u603b/I1
\u56e0\u4e3a I1\u3008 I\u603b
\u6240\u4ee5 R1 \u3009R\u603b
而电阻都可以理解为导线做成的,串联就相当于导线的长度增加了,所以总电阻会比里面的每个电阻都大
而并联则相当于增加了导线的截面积,就算是并联支路最小的电阻的截面积也增加了,所以总电阻会比每个电阻都小。
并联电路:
1/R=1/R1+1/R2+...+1/Rn > 1/Ri(i=1,2...n)
1/R> 1/Ri
R < Ri
并联电路中,电压固定,电流i总=i1+i2+i3+i4+......,电阻R=u/i,电流越大,电阻越小。
等于是导体的横截面积变大了
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