(1)电流$I=\frac{U_{2}}{R_{2}}=\frac{6\ \text{V}}{60\ \Omega}=0.1\ \text{A}；$
(2)$R_{1}$两端电压$8\ \text{V}-6\ \text{V}=2\ \text{V}，$$R_{1}=\frac{2\ \text{V}}{0.1\ \text{A}}=20\ \Omega；$
(3)电流0.2 A时，总电阻$R_{\text{总}}=\frac{8\ \text{V}}{0.2\ \text{A}}=40\ \Omega，$$R_{2}=40\ \Omega-20\ \Omega=20\ \Omega，$电压表示数$U=0.2\ \text{A}\times20\ \Omega=4\ \text{V}。$
