> It doesn't even begin to explain to me what it measures or how it applies to an actual circuit. What components of a circuit have an impedance? If I increased

> It doesn't even begin to explain to me what it measures or how it applies to an actual circuit. What components of a circuit have an impedance? If I increased the impedance, what would happen? How would I even do that? That's all in his post: >>> We get it by taking the Laplace transform of the differential equation that defines the relationship between current and voltage in a capacitor or inductor. I = C dV/dt Laplace(dV/dt) = V*s I = C * V * s V / I = 1 / (C * s) V = L dI/dt Laplace(dI/dt) = I*s V / I = L * s Granted, he doesn't take the extra step to say that Z = V/I. Once you see that, you can see that impedance is proportional to inductance and frequency or inversely proportional to capacitance and frequency. (I feel that your participation in this discussion implies that you know what V, I, C, and L stand for.) > I know that anything that has resistance or reactance also has impedance, and something that has both has even more impedance, Everything has resistance and reactance. 0 is still a number. It also doesn't follow that two non-zero numbers are greater than one non-zero numbers. > but in a DC circuit where the frequency is zero you'd get some edge condition where a non-zero reactance would, let's see, act as infinite resistance, I think? There are incredibly few "DC" circuits. Most of what you'd think to call DC circuits are actually switched circuits, which have transient or AC properties. You're right that after settling, a capacitor acts as an open, however an inductor acts as a short. Your intuition failed you here.