We have just started to look at transmission lines/coaxial cables in one of my classes. This uses the concept of having 2 wires close together causing an impedance/capacitance that allows/controls propagation. However I have never really considered how electricity propagates in the first place. Surely electricity could propagate over 1 lead if the respective terminals where connected to ground? In these models that would be impossible. How does electricity propagate typically? Is it affected by the inductance/capacitance between two leads? Or is the transmission line theory just for high frequency signal propagation?