There were two threads in short succession in this forum about basic electric circuitry (RC circuit, RL circuit), and it struck me that over the years I've been surprised that the "water circuit" analogy isn't used more than it is. That is, in a system with a circular pipe that contains water: Electrons = Water molecules Battery = Pump Voltage = Water pressure Current = Water flow Resistor = Narrow pipe Now, what would the equivalents of the capacitor and the coil be? That's what I've been wondering. EDIT: Ooh, a coil could be imagined as a heavy flywheel that is moved by the water current. It will oppose any change in flow through it.