Question

明早要用的!,电压表与R2并联,R2与R1串联,电流表测R1的.

Answer 1

(U-4.5)/4.5=R1/R2

(U-3)/3=R1/(R2/2)

二式相比,得:(U-4.5)/(U-3)=3/4

可解得,电源电压为:U=9V

则由(U-4.5)/4.5=R1/R2,得

R2=R1*4.5/(U-4.5)=3*4.5/(9-4.5)=3欧

P在R2的最大电阻处时,I=4.5/R2=4.5/3=1.5A

P在R2的中点时,I'=(U-U2')/R1=(9-3)/3=2A