Question

giải giúp minh với

Answer 1

\(a,R2ntR1\\ R_{td}=R_1+R_2=30\Omega\\ I=\dfrac{U}{R_{td}}=\dfrac{54}{30}=1,8A\\ b,U_{MP}=I_2R_2=I_3R_3\\ \Rightarrow\dfrac{I_2}{I_3}=\dfrac{R_3}{R_2}=\dfrac{1}{2}\\ \Rightarrow R_3=\dfrac{R_2}{2}=9\Omega\\ R_{td}=\left(R_2//R_3\right)ntR_1=\dfrac{R_2R_3}{R_2+R_3}+R_1=\dfrac{18.9}{18+9}+12=18\Omega\)  

\(I'=\dfrac{U}{R_{td}}=\dfrac{54}{18}=3A\)