\draw (0, 0) to [V=$V_s$](0, 2)
to [R=$R_1$](2, 2)
to [R=$R_2$](4, 2)
to (4, 0) to (0, 0);
并联时，电流按电阻值比例进行奇怪的分流（分配电流）
\draw (0, 0) to [short, i=$I_{all}$](2, 0)
(2, 0) to (2, 1)
to [R=$R_1$](4, 1)
(2, 0) to (2, -1)
to [R=$R_2$](4, -1);
Just to be clear, all those things are based on ohm's law.
