5.
η=R/(R+r)<=>ηR+ηr=R<=>R(1-η)=ηr=>R=ηr/(1-η)=0,8r/(1-0,8)=0,8r/0,2=4r
R=4r
b)
S ||
a) Rp=R₂R₃/(R₂+R₃)=6*3/(6+3)=18/9=2 Ω
Re=R₁+Rp=7+2=9 Ω
b)U₂=U₃=>I₂R₂=I₃R₃<=>6I₂=3I₃=>I₃=2I₂
I=I₂+I₃<=>1,2=I₂+2I₂<=>1,2=3I₂=>I₂=1,2/3=0,4 A
c) E=I(R₁+r)+I₂R₂<=>12=1,2(7+r)+0,4*6<=>12-2,4=1,2(7+r)<=>8=7+r=>r=8-7=1 Ω
d) U₂=I₂R₂=0,4*6=2,4 V
