What's Wrong with the Water circuit analogy?

Since a water circuit involves common visible phenomena, the analogy with a water circuit can give some quick perspective about the behavior of a simple DC electric circuit. There are many clear-cut parallels in behavior, particularly from an energy perspective. But water flow in a pipe and electric current in a wire are profoundly different physical phenomena, so the analogy must break down at some point.

For some applications, the water analogy is actively discouraged as being misleading. Thane Heins relates the advice of a professor "Our Motors and Generators Concepts professor in college always warned us students to stay away from the 'water' analogy which tends to lead us astray because it fails to take into account the magnetic field energy produced around all current bearing wires and especially the work this energy does when producing the counter-electromotive-torque/work produced inside all electric generators and the change in kinetic energy of the system this work performs when generators are placed on-load." In his critique of the water analogy, he points out several situations where an application of the water analogy would be misleading.

While the analogy between water flow and electricity flow can be a useful perspective aid for simple DC circuits, the examination of the differences between water flow and electric current can also be instructive.

Voltage-Pressure Analogy

A battery is analogous to a pump in a water circuit. A pump takes in water at low pressure and does work on it, ejecting it at high pressure. A battery takes in charge at low voltage, does work on it and ejects it at high voltage.