I'm in EE and I've taken a fair bit of both circuit theory and EM theory, but I've always struggled a little bit with connecting the two. I think my main issue is that textbooks are usually very clear about how they've defined resistance, capacitance and inductance, but then they're not so clear about justifying those definitions, except in very simple cases. In particular, it seems that they're justified separately from one another (e.g., the definition of capacitance is justified only when there aren't any resistive or inductive effects present) but then we use them all simultaneously. I end up feeling like we calculate a bunch of values by dividing integrals by other integrals, and we call those things "inductance" or "capacitance" or "resistance," and then plug them into a circuit accordingly, but I've never really seen a clear justification that the network of resistors, capacitors, and inductors I end up with is actually a good approximation of the full field/source analysis. Are there any books that go through a thorough analysis of this sort of thing? Something that really "bridges the gap" between Maxwell's equations and the circuits that we use to approximate them? Thanks.