Khi K mở:
\(R_3nt\left[\left(R_1ntR_2\right)//R_4\right]\)
\(R_{12}=R_1+R_2=8+4=12\Omega\)
\(R_{124}=\dfrac{R_{12}\cdot R_4}{R_{12}+R_4}=\dfrac{12\cdot6}{12+6}=4\Omega\)
\(R_{tđ}=R_3+R_{124}=4+4=8\Omega\)
\(I_A=I_m=\dfrac{U}{R}=\dfrac{6}{8}=0,75A\)
Khi K đóng:
\(R_1//\left[R_4nt\left(R_2//R_3\right)\right]\)
\(R_{23}=\dfrac{R_2\cdot R_3}{R_2+R_3}=\dfrac{4\cdot4}{4+4}=2\Omega\)
\(R_{234}=R_4+R_{23}=6+2=8\Omega\)
\(R_{tđ}=\dfrac{R_1\cdot R_{234}}{R_1+R_{234}}=\dfrac{8\cdot8}{8+8}=4\Omega\)
\(I_{234}=\dfrac{U_{234}}{R_{234}}=\dfrac{U}{R_{234}}=\dfrac{6}{8}=0,75A\)
\(U_4=I_4\cdot R_4=I_{234}\cdot R_4=0,75\cdot6=4,5A\)
\(U_{23}=U-U_4=6-4,5=1,5V\)
\(I_A=I_3=\dfrac{U_3}{R_3}=\dfrac{U_{23}}{R_3}=\dfrac{1,5}{4}=0,375A\)
