\(R=R1+\left(\dfrac{R2.R3}{R2+R3}\right)=15+\left(\dfrac{30.30}{30+30}\right)=30\Omega\)
\(U23=U3=U2=R2.I2=30.0,50=15V\)(R2//R3)
\(\Rightarrow I=I1=I23=U23:R23=15:\left(\dfrac{30.30}{30+30}\right)=1A\)(R1ntR23)
\(\Rightarrow U=R.I=30.1=30V\)
Chọn A
\(R_{23}=\dfrac{R_2.R_3}{R_2+R_3}=\dfrac{30.30}{30+30}=15\left(\Omega\right)\)
\(U_{23}=U_2=U_3=I_2.R_2=0,5.30=15\left(V\right)\)
\(R_{tđ}=R_1+R_{23}=15+15=30\left(\Omega\right)\)
\(I=I_1=I_{23}=\dfrac{U_{23}}{R_{23}}=\dfrac{15}{15}=1\left(A\right)\)
\(U_{AB}=I.R_{tđ}=1.30=30\left(V\right)\)