Ro=10欧,若S在a时,电压表示数为3V.S在b时,电压表示数为4V,且R2=2R1,求电源电压U和R1,R2阻值.

(10 + R1) x (3 / R1) = U
(10 + R2) x (4 / R2) = U --> R2 = 2R1
(10 + 2R1) x (4 / 2R1) = U
(10 + R1) x (3 / R1) = U
------------------------ ---
(10 + 2R1) x (4 / 2R1) = U
(10 + R1) x 3
----------------- = 1
(10 + 2R1) x 2
30 + 3R1 = 20 + 4R1
R1 = 10 欧姆
R2 = 20 欧姆
U = (3 / 10) x (10+10) = 6V