ClearAll["Global`*"]  (* Multiple Examples, Class 15 *)
;
answers=DSolve[{i1[0]==0,v0-v1[t]==i1[t] R, v1[t]== L  i1'[t]},{v1[t],i1[t]},t][[1]];
v1[t_]=v1[t]/.answers//Expand;
Print["(Subscript[V, 1])(t) = ",v1[t]]

ClearAll["Global`*"]
R1=200.0;R2=50.0;c=25*(10^(-3));v0=10.0;
;
answers=DSolve[{v0-v1[t]==R1 i1[t],-va[t]==2 v0,v1[t]-va[t]==R2 i2[t],i3[t]==c v1'[t],i1[t]==i2[t]+i3[t],v1[0]==v0},{v1[t],i1[t],i2[t],i3[t],va[t]},t][[1]];
v1[t_]=v1[t]/.answers//Expand;
Print["(Subscript[V, 1])(t) = ",v1[t]]

ClearAll["Global`*"]
;
answers=DSolve[{36.0-v3[t]==2 i1[t],v3[t]==4 i3[t],v1[t]-v2[t]== 6 i2[t],-v2[t]==2 i3[t],i1[t]==i2[t]+i3[t],v3[t]-v1[t]==3 i2'[t],i2[0]==3.0},{v1[t],v2[t],v3[t],i1[t],i2[t],i3[t]},t][[1]];
i2[t_]=i2[t]/.answers//Expand;
Print["(Subscript[i, 2])(t) = ",i2[t]]

ClearAll["Global`*"]
;
c=100*(10^(-6));R1=6000.0;R2=4000.0;R3=8000.0;v0=9.0;
v2a[t_]=0.0;answersB=DSolve[{v0-v1[t]==R1 i1[t],v1[t]-v2[t]==R2 i3[t],v2[t]==R3 i3[t],i2[t]==c v1'[t], i1[t]==i2[t]+i3[t],v2[0]==0},{v1[t],v2[t],i1[t],i2[t],i3[t]},t][[1]];
v2b[t_]=v2[t]/.answersB//Expand;
Print["(Subscript[v, 2  B])(t) = ",v2b[t]]
v0=0.0; (* Voltage is now switched off! *)
(* start a new "clock" t2 = t - 0.3 *)
answersC=DSolve[{v0-v1[t2]==R1 i1[t2],v1[t2]-v2[t2]==R2 i3[t2],v2[t2]==R3 i3[t2],i2[t2]==c v1'[t2], i1[t2]==i2[t2]+i3[t2],v2[0]==v2b[0.3]},{v1[t2],v2[t2],i1[t2],i2[t2],i3[t2]},t2][[1]];
v2c[t2_]=v2[t2]/.answersC//Expand;
Print["(Subscript[v, 2  C])(t) = ",v2c[t2]]
Plot[Piecewise[{{v2a[t],t<0},{v2b[t],0<t<0.3},{v2c[t-0.3],t>0.3}}],{t,-1,2},PlotRange-> {{-1,2},{0,4}}]

ClearAll["Global`*"]
;
R=100.0;c=4*(10^(-3)); L = 5.0; v0 = 20.0;
answers=DSolve[{v0-v1[t]==R i1[t],i1[t]==c v2'[t],v1[t]-v2[t]== L i1'[t],i1[0]==0,v2[0]==10.0},{i1[t],v1[t],v2[t]},t][[1]];
i1[t_]=i1[t]/.answers//Expand;
Print["(Subscript[i, 1])(t) = ",i1[t]]