Theo bài ra, ta có: Rtđ = R1 + R23 = R1 + R2.R3/R2+R3 = 8+ 20.30/20+30= 8+12=20 (ôm)
=> I = U/Rtđ = 40/20 = 2 (A)
Vì R1nt(R2//R3) nên, suy ra: I1=I2+I3=I=2 (A)
=> U23=I23.R23= 12.2=24 (V)
Vì R2//R3 nên, suy ra: U2=U3=U23= 24 (V)
=> I2=U2/R2= 24/20=1.2 A
I3=U3/R3= 24/30= 0,8 A