萧锋晨
春芽
共回答了16个问题采纳率:81.3% 举报
R1电阻为100欧时,电路中的电流I=U/R=U/(R2+100欧)
此时电阻R2消耗的电功率P2=I² R2=U² R2/(R2+100欧)²
R1电阻为20欧时,电路中的电流I'=U/R'=U/(R2+20欧)
此时电阻R2消耗的电功率P2'=I'² R2=U² R2/(R2+20欧)²
∵P2'=4P2
∴U² R2/(R2+20欧)² =4U² R2/(R2+100欧)²
∴1/(R2+20欧)² =4/(R2+100欧)²
∴1/(R2+20欧)=2/(R2+100欧)
∴R2+100欧=2(R2+20欧)
∴R2=60欧.
答:R2的阻值为60欧.
1年前
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zexwhy
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“1/(R2+20欧)² =4/(R2+100欧)²”是怎么到 "1/(R2+20欧)=2/(R2+100欧)"和 “R2+100欧=2(R2+20欧)"的?
举报
萧锋晨
“1/(R2+20欧)² =4/(R2+100欧)²”开根号到"1/(R2+20欧)=2/(R2+100欧)" "1/(R2+20欧)=2/(R2+100欧)"十字交叉相乘到“R2+100欧=2(R2+20欧)"