\(R_{12}=\dfrac{R_1R_2}{R_1+R_2}=\dfrac{4\cdot4}{4+4}=2\left(\Omega\right)\)

\(R_{34}=R_3+R_4=3+5=8\left(\Omega\right)\)

\(R_{345}=\dfrac{R_5R_{34}}{R_5+R_{34}}=\dfrac{8\cdot8}{8+8}=4\left(\Omega\right)\)

\(R_{tđ}=R_{12}+R_{345}=2+4=6\left(\Omega\right)\)

\(I_{12}=I_{345}=I=\dfrac{U}{R_{tđ}}=\dfrac{12}{6}=2\left(A\right)\)

\(U_1=U_2=U_{12}=I_{12}\cdot R_{12}=2\cdot2=4\left(V\right)\)

\(U_5=U_{34}=U_{345}=I_{345}\cdot R_{345}=2\cdot4=8\left(V\right)\)

\(I_1=\dfrac{U_1}{R_1}=\dfrac{4}{4}=1\left(A\right)\)

\(I_2=\dfrac{U_2}{R_2}=\dfrac{4}{4}=1\left(A\right)\)

\(I_3=I_4=I_{34}=\dfrac{U_{34}}{R_{34}}=\dfrac{8}{8}=1\left(A\right)\)

\(I_5=\dfrac{U_5}{R_5}=\dfrac{8}{8}=1\left(A\right)\)

Những điện trở này nối tiếp hết đúng ko bạn?

Bạn cần ghi rõ đề là nó được mắc nối tiếp hay song song nha bạn!

\(R_{12}=\dfrac{R_1\cdot R_2}{R_1+R_2}=\dfrac{12\cdot6}{12+6}=4\Omega\)

\(R_{34}=R_{tđ}-R_{12}=10-4=6\Omega\)

\(\dfrac{1}{R_{34}}=\dfrac{1}{R_3}+\dfrac{1}{R_4}=\dfrac{1}{24}+\dfrac{1}{R_4}=\dfrac{1}{6}\)

\(\Rightarrow R_4=8\Omega\)

không thể tìm được bạn ạ :D

U đâu mà tìm

\(=>R4//\left[R1nt\left(R2//R3\right)\right]\)

\(=>U4=U123=U=120V\)

\(=>I4=\dfrac{U4}{R4}=\dfrac{120}{20}=6A\)

\(=>I123=\dfrac{U123}{R123}=\dfrac{120}{R1+\dfrac{R2.R3}{R2+R3}}=\dfrac{120}{20+\dfrac{20.20}{20+20}}=4A=I23\)

\(=>U23=I23.R23=4.\dfrac{20.20}{20+20}=40V=U3\)

\(=>I3=\dfrac{U3}{R3}=\dfrac{40}{20}=2A\)

\(=>Ia=I4+I3=2+6=8A\)