# Query regarding a published description of a mechanical hydraulic system analogous to $V = IR$ in an electrical system The screenshot is taken from the wikipedia article for a resistor - https://en.wikipedia.org/wiki/Resistor

I understand that a larger head results in greater hydrostatic pressure, therefore a greater pressure gradient (analogous to potential difference).

I take it that a clogged sink increases the "resistance" to flow due to less cross-sectional area for the fluid to move through, like how the cross-sectional area of a wire is inversely proportional to electrical resistance.

But what I don't understand is, in the hydraulic analogy, what they actually mean by "flow".

"When the pipe is clogged, it takes a larger pressure to achieve the same flow of water”.. - What does "flow" actually mean in this context?

I'm assuming it's not flow rate as I believe, in accordance with the continuity equation, that that quantity remains constant for the given system regardless of any area increase/decrease. And it can't be flow velocity as, for the clogged sink, that will surely increase. So how does the flow actually decrease?

• If you have difficulties with the hydraulic system, what is the point in using it to model the electric phenomena? The fluid mechanics is at least as complicated as electrical circuits phenomena. If not more complicated.
– nasu
Sep 10, 2021 at 20:32

• Equations mostly just express the things we have already proved. Does it matter whether I say $A_1v_1=A_2v_2$ or whether I say "all cross-sections of a system have the same flow rate as each other"? Because how do you know what $A_1$ and $A_2$ are? I'd have to explain it in words anyway. Sep 10, 2021 at 15:36