I am NOT trying to solve this as a homework problem, I'm just trying to dig out basic concepts that I'm missing when using this battery+resistance diode model. I'm having trouble seeing why, when solving for current, KCL equation does NOT work out as: 1) I= (0-Va)/rd 2) I=(Va-(-5))/R where Va is the voltage at node a, rd is the diode resistance, and Vd0 is the diode voltage drop. I understand that the resistors are in series, and there is only one current, so the correct Kirchoff's equation should be: I=(0-Vd0)/(rd+R) But each resistor is responsible for a (different) voltage drop. The position of the resistors, even if they are in series, is specific. We can see this by measuring voltages before and after a resistor. Hopefully somebody can provide a fullproof explanation for this.