a, R1 nt [(R2 nt R3) // (R4 nt R5)] => RAB=\(R_1+\dfrac{\left(R_2+R_3\right)\left(R_4+R_5\right)}{R_2+R_3+R_4+R_5}=18\left(\Omega\right)\)
IAB=UAB/RAB=24/18=4/3(A)
Ta có: \(\dfrac{I_{23}}{I_{45}}=\dfrac{R_{45}}{R_{23}}=\dfrac{R_4+R_5}{R_2+R_3}=1,5\left(A\right)\Rightarrow\dfrac{I_{23}}{3}=\dfrac{I_{45}}{2}=\dfrac{I_{AB}}{5}=\dfrac{4}{15}\left(A\right)\Rightarrow\left\{{}\begin{matrix}I_{23}=0,8\left(A\right)\\I_{45}=\dfrac{8}{15}\left(A\right)\end{matrix}\right.\)
R2 nt R3 => I2 = I3 = I23 = 0,8A
R4 nt R5 => I4 = I5 = I45 = 8/15 ≃ 0,53A
R1 nt [(R2 nt R3) // (R4 nt R5)] => I1 = IAB = 4/3 ≃ 1,33A
b, UAN=U1 + U4 = I1.R1 + I4.R4 = 19,2V
UMN=UMB+UBN=U3-U5=I3.R3-I5.R5=0
