初二物理题：两个定值电阻R1，R2，R1=2R2，先并联在电压为U的电路中，功率分别为
\u4e24\u4e2a\u5b9a\u503c\u7535\u963bR1\u548cR2\uff0c\u4e14R1\uff1eR2\uff0e\u82e5\u5c06\u5b83\u4eec\u4e32\u8054\u540e\u63a5\u5728\u7535\u538b\u4e3aU\u7684\u7535\u8def\u4e0aR1\u548cR2\u6d88\u8017\u7684\u529f\u7387\u5206\u522b\u4e3aP1\u548cP2\uff1b\u82e5\u5c06\uff081\uff09\u5f53\u4e24\u4e2a\u5b9a\u503c\u7535\u963bR1\u548cR2\u4e32\u8054\u65f6\uff0c\u901a\u8fc7\u5b83\u4eec\u7684\u7535\u6d41\u76f8\u7b49\uff0c\u2235R1\uff1eR2\uff0c\u2234\u6839\u636eP=I2R\u53ef\u77e5\uff0cP1\uff1eP2\uff1b\uff082\uff09\u5f53\u4e24\u7535\u963b\u5e76\u8054\u65f6\uff0c\u4e24\u7535\u963b\u4e24\u7aef\u7684\u7535\u538b\u76f8\u7b49\uff0c\u2235R1\uff1eR2\uff0c\u2234\u6839\u636eP=U2R\u53ef\u77e5\uff0cP1\u2032\uff1cP2\u2032\uff1b\uff083\uff09\u6839\u636e\u4e32\u8054\u7535\u8def\u7535\u963b\u7684\u5206\u538b\u7279\u70b9\u53ef\u77e5\uff0cR1\u5e76\u8054\u65f6\u4e24\u7aef\u7684\u7535\u538b\u6bd4\u4e32\u8054\u65f6\u4e24\u7aef\u7684\u7535\u538b\u5927\uff0c\u6839\u636eP=U2R\u53ef\u77e5\uff0cP1\uff1cP1\u2032\uff0c\u2234P2\uff1cP1\uff1cP1\u2032\uff1cP2\u2032\uff0e\u7ed3\u5408\u9009\u9879\u53ef\u77e5\uff0cABC\u5747\u4e0d\u6b63\u786e\uff0cD\u6b63\u786e\uff0e\u6545\u9009D\uff0e
\uff081\uff09\u7535\u963b\u4e32\u8054\u7535\u8def\uff1a\u7535\u6d41\u76f8\u7b49
\u6839\u636e\u7535\u529f\u7387\u516c\u5f0fP\uff1dI\uff3e2*R\u53ef\u77e5
P1\uff1dI\uff3e2*R1\uff1d0.02*0.02*250\uff1d0.1\uff08W\uff09
P2\uff1dI\uff3e2*R2\uff1d0.02*0.02*500\uff1d0.2\uff08W\uff09
\u6240\u4ee5P1\uff1aP2\uff1d1\uff1a2
\uff082\uff09\u9009\u62e9B
\u7535\u963b\u5e76\u8054\u7535\u8def\uff1a\u7535\u538b\u76f8\u7b49\uff0c\u7535\u6d41\u76f8\u52a0
\u6839\u636e\u6b27\u59c6\u5b9a\u5f8bI\uff1dU/R\u53ef\u77e5
\u7535\u6e90\u7684\u7535\u538bU\uff1dI1*R1\uff1d0.3*10\uff1d3\uff08V\uff09
\u6545C\u662f\u9519\u8bef\u7684
\u901a\u8fc7\u7535\u963bR2\u7684\u7535\u6d41I2\uff1dI-I1\uff1d0.5-0.3\uff1d0.2\uff08A\uff09
\u6545A\u662f\u9519\u8bef\u7684
\u6839\u636e\u6b27\u59c6\u5b9a\u5f8bI\uff1dU/R\u53ef\u77e5
\u7535\u963bR2\u7684\u963b\u503cR2\uff1dU/I2\uff1d3/0.2\uff1d15\uff08\u6b27\u59c6\uff09
\u6545B\u662f\u6b63\u786e\u7684
\u6839\u636e\u7535\u529f\u7387\u516c\u5f0fP\uff1dU\uff3e2/R\u53ef\u77e5
P1\uff1dU\uff3e2/R1\uff1d3*3/10\uff1d0.9\uff08W\uff09
\u6545D\u662f\u9519\u8bef\u7684
P2\uff1dU\uff3e2/R1\uff1d3*3/15\uff1d0.6\uff08W\uff09
\u6240\u4ee5P1\uff1aP2\uff1d3\uff1a2
P1＝U^2/R1
P2＝U^2/0.5R1
串联时，电压之比等于电阻之比：
P3＝（2U/3）^2/R1
P4＝（U/3）^2/0.5R1
所以：P1：P2：P3：P4＝9：18：4：2
并联：P＝U^2/R1＋U^2/0.5R1
串联：P‘＝U^2/(R1＋0.5R1）
所以：P：P'＝9：2
不明追问。
先是并联，U相同，P1=U的平方/R1，P2=U的平方/R2=2*U的平方/R1,
后是串联，I==U/(R1+R2)相同，P3=I的平方*R1,P4=I的平方*R2=2*I的平方*R1
所以：P1：P2：P3：P4＝9：18：4：2
望采纳！！！
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