luckyjuan
春芽
共回答了24个问题采纳率:95.8% 举报
P在b端时,则有:U=3v/R1(R1+R2+R3)-----①
P在a端时,则有:
U=9V/R1(R1+R2)------②
因为U不变,所以:
R1+R2+R3=3(R1+R2),即R3=2(R1+R2)----③
P在中点时,则有:
U=0.45A×(R1+R2+12R3)----④
③代入④式得:
U=0.45A×(R1+R2+R1+R2)=0.9A×(R1+R2)--⑤
因电源的电压不变,
所以由②⑤两式可得:
9VR1(R1+R2)=0.9A×(R1+R2),即9VR1=0.9A,
解得:R1=10Ω;
R3=2(R1+R2)=2×(10Ω+20Ω)=60Ω;
U=9V10Ω×(10Ω+20Ω)=27V.
答:(1)电阻R1的阻值为10Ω;
(2)滑动变阻器R3的最大阻值为60Ω;
(3)电源电压为27V.
1年前
10