Hello. Resistive Ohm's law is famously known as V = IR. We can derive its microscopic version as being followed. V = El, where E and l are, respectively, an electric field and a resistive load length over which a voltage drop V is developed. I = JS, J and S are a current density and a cross-sectional area of the load (uniform cross-section is assumed). Substituting these expressions into the Ohm's law gives El = JSR → J = σE where σ = l/(SR) or R = l/(σS). It is very obvious that J = σE is the microscopic version of the Ohm's law of V = IR. It looks that J = σE is only true for resistive load and DC. I would like to know if there is any microscopic version of generalized Ohm's law of V = IZ where Z is an impedance. Could we find this?