[tex]R=1.5r\Rightarrow r=\frac{R}{1.5}=\frac{2}{3}R[/tex]
Aplicam legile lui Kirchoff pe intregul circuit
[tex]E=I*(R+r)=I*(R+\frac{2}{3}R)=I*R*\frac{5}{3}[/tex]
Tensiunea electrica U are formula
[tex]U=I*R[/tex]:Atunci
[tex]E=\frac{5}{3}*U\Rightarrow U=\frac{3}{5}*E=9/5=1.8V[/tex]
