Talk:Hydraulic analogy

Lack of References
There are no references on the page. I am an amauteur user but even I can see this must be addressed

I would like to add that this article is missleading. Don't use it. Examples: 1. The proper analogy is between voltage and hydraulic head - not pressure (both represent the potential energy) 2. The proper analogy is between capacitors and tanks. 3. The proper analogy is between Resistors and Pipes althogh ohm's law is not linear. 4. The proper analogy is between "Ground" and "Sea level" as reference. 3. The proper analogy is between a transistor and a valve. etc.

The main differences are: 1. There is no concept symetric to pressure in electric circuits. 2. The concept of loops is different. Water may not return to the source. 89.138.203.18 (talk) 21:58, 13 April 2009 (UTC)


 * I disagree that there's a good analogy between capacitors and tanks. In a capacitor, extra charge is added to one side and subtracted from the other side. In a tank, water is added to the tank but not subtracted from anywhere. In other words, water can flow into a tank with no outlet, but that does not work for a capacitor, which needs a wire with current flowing in AND a different wire with current flowing out. I think the rubber diaphragm in a steel pipe works much better.
 * I edited a bit to mention that hydraulic head was better, but pressure is OK as long as the water is flowing horizontally. --Steve (talk) 20:25, 27 April 2012 (UTC)

Goal
This site says: "Many writers eventually resort to some kind of water analogy to try to explain how electricity works. I have yet to see what I thought was a really good water analogy. If you want to explain electricity, talk about electricity. Hydraulics is another field entirely. Avoid this trap; it is already full."

Although I agree that most such analogies are done poorly, the potential exists for a perfectly accurate one, as they are both fluids flowing down conduits. I hope to make a page for the wikipedia that collects these ideas together into a coherent whole that the naysayers and nitpickers can then edit to perfection. - Omegatron

So I had this in my user space until it evolved into something vaguely encyclopedic, and then merged it with the pre-existing article which was just a table of related equations. Now that it is in the main article space it should evolve a lot faster. - Omegatron 02:48, July 12, 2005 (UTC)

Already I can see problems because the links are taken from websites that don't appear to be credible. If anything, they appear to be the incoherent jibberings of clueless amateurs. Take for example how pressure is equated with voltage. I'm afraid this doesn't make sense to me since pressure is what moves the liquid and so would be better equated with the electrical field since this moves charge. Secondly, unlike pressure, there is no such thing as voltage existing at a point. Voltage measures the energy gained or lost when charge moves between points and so is always referenced to two points. If you want a hydraulic analogy of voltage, then this will have to be equivalent to the energy lost or gained when a certain volume of water is transferred between two points. i.e. the change in (KE + PE). —Preceding unsigned comment added by 80.47.114.136 (talk • contribs)
 * You're only half-correct.  Potential (voltage) can be described two ways: joules per coulomb for transporting a test-charge, but Potential also is the line-integral of the e-field.  Because of the latter, electric fields can be described directly in terms of Potential, without referring to energy, as planes (shells) of equipotential.  In other words, voltage is simply a way to describe e-fields.  Volts/meter is fundamental, it's the field, while volts = joules/coulomb comes from the transport of a test-charge *through* a field, a field which is composed of volts/meter values.) 208.38.200.183 (talk) 14:33, 21 April 2014 (UTC)

Cdang's version

 * it helps a lot understanding the difference between potential and voltage:
 * potential &rarr; altitude, or pressure;
 * voltage &rarr; difference in height between the top and the bottom of the water circuit (height of the water column), or difference of pressure between upstream and downstream;
 * parallel components can be compared with communicating vessels (same voltage~same difference of pressure) and with a flow derivation (Kirchhoff's current law);
 * What do you mean by "communicating vessels"? - Omegatron
 * resistance can be compared with friction (loss of charge, pressure drop):
 * resistance of the wire &rarr; friction in the pipe;
 * resistor &rarr; sinuous pipe such as heat exchanger;
 * load of an active component (e.g. charging accumulator, motor, electrolysis) can be compared with a watermill or a turbine;
 * back electromotive force &rarr; force used to make the turbine turn.

Unfinished
Moving some things here so that I can turn this into a real article:


 * Transformer : like an AC piston that moves back and forth, connected externally to another such piston by a lever with a pivot in the middle. the amount of lever on each end determines the ratio, and it can only transfer AC.  (of course DC at that point in the circuit would change something? hmm... [No, it only works with AC, since a transformer pretty much works by one "inductor" affecting another]).  This is similar to a hydraulic transformer.  A "fluid coupling transmission"?

I hope to make a better version of this




 * Of course a transformer works with DC. Check out this flyback DC-DC converter.  That's pure DC running through the transformer.
 * I.e., a transformer hydraulic analogy isn't that complex. It's basically two water turbines (inductors) connected by different-sized gears.  The two water pipe systems are isolated, but when one turbine spins, it forces the other to spin at a ratio determined by the gears. -Dragonchild (12.27.39.105 (talk) 15:53, 28 November 2007 (UTC))
 * That analogy would work if a transformer could induce a constant DC output on its secondary if given a constant DC input on the primary. The various examples given here show the most basic operation, but they all leave out a critical step or in the general operation of a transformer.  Here's how I would do it:
 * [[Image:Isolated AC-only Fluid Transducer (transformer) TEST.png]]
 * Start with a simple cylinder with a thin "plate" piston in it.
 * Place a spring on each side between the piston and the facing cylinder wall, so that the piston's natural position is centered along the cylinder's length.
 * Connect a pipe to each end of the cylinder. As fluid pushes the piston from one end, fluid should be pushed out the other end.
 * Connect a bidirectional delay valve to a tee on each of the two pipes. "AC" current would move the piston around, but a constant "DC" current would force the valve to open and thus mostly bypassing the piston.
 * Attach a push rod to the piston and pass it out of the assembly, through a sealed hole.
 * Now, construct a second such apparatus, perhaps with a different-sized piston/cylinder.
 * Securely fasten the two assemblies to a base so that the push rods point at each other, and fasten the two push rods together.
 * The amount of delay in each bypass valve together with the size of the piston basically determine the resonant frequency of each side, while the relationship between the sizes of the two pistons of course determines the ratio of the transformer as a whole.Vanessaezekowitz (talk) 10:13, 26 March 2008 (UTC)

Original talk page
I have started this article independently. :-) They will be folded together when it is ready.  See User:Omegatron/water analogy - Omegatron 21:42, May 24, 2005 (UTC)

Should this be renamed Hydraulic analogy to electric circuits? - Omegatron 21:42, May 24, 2005 (UTC)


 * Oh I see there is a heat analogy, too. Hmmm...  - Omegatron 21:46, May 24, 2005 (UTC)

I look forward to seeing this article made more complete. The heat analogy is very important historically and I think it should remain in the article and linked to Caloric theory. That being said, I think the analogy for heat is less perfect--I don't know of a thermal equivalent of a transistor, for instance, so it makes sense to me to go into more detail with the hydraulic-electric pair. --Scentoni 06:32, 25 May 2005 (UTC)


 * So, the heat analogy intuitively replaces an invisible form of energy with. . . another invisible form of energy? If there's historical significance let's put it in there for completeness' sake, but I've never heard of someone successfully explaining electrodynamics in terms of heat.  Personally, I found thermodynamics HARDER to understand than electrodynamics. -Dragonchild (12.27.39.105 (talk) 15:58, 28 November 2007 (UTC))


 * Hmmm... maybe keep the article name "Hydraulic analogy", and have a section for electrical analogy and a small section for heat analogy at the end? - Omegatron 13:50, May 25, 2005 (UTC)

Botched merge
So I attempted to merge my userfied version with the actual version, but accidentally moved the talk page over top of the article instead of the talk page, undeleted the old history before I realized it, blah blah etc. Anyway, the end result is that some of the original article's history is now in the talk page history. Sorry. All the info's still there, but it is for the wrong page. - Omegatron 02:42, July 12, 2005 (UTC)

Rectilinear transformer
http://virtual.cvut.cz/dynlab/courseModeling/node42.html

Failures of the model
I've added a section about the limits of the analogy. (Useful analogies can lead to serious misconceptions when we don't know when to drop them, and instead use a better model.) — Preceding unsigned comment added by Wjbeaty (talk • contribs) 20:12, 4 April 2006 (UTC)

2D would be clearer
although the 3d images are nice, 2d would be much clearer. —Preceding unsigned comment added by Laplacian (talk • contribs) 02:03, 13 May 2008 (UTC)
 * 2D images might be a little easier to make sense of, perhaps. I've replaced those low-resolution 3D images I drew sometime back with nicely detailed SVG's, which should eliminate the clarity problem altogether.  Besides, 3D images just look better than 2D. Vanessaezekowitz (talk) 08:49, 22 July 2009 (UTC)

Inductors
Might it be better to describe inductance as a turbine instead, or in addition to, a paddle wheel? It seems easier to visualize a turbine as part of a closed hydraulic system as opposed to a paddle wheel, which really only works in a hydraulic analogy that includes gravity. —Preceding unsigned comment added by 128.118.147.10 (talk) 20:26, 30 May 2008 (UTC)
 * I have considered turbines as a model for inductors. Although I have done calculations and found certain models to be mathematically correct, creating a real world physical model of one would be tedious. You see, I reckon that for it to fully represent how an induction coil behaves, it would have to be a turbine such that water can only flow through it if the blades of the turbines move. Also, it would be ideal if the velocity of the blades of the turbine always match that of the water.--Jocajo 22:18, 28 november 2011 (UTC+1)

So I've created this picture of a model for an inductor. It basically already fits the description in the article. Being the quantity that relates applied pressure to acceleration of the current, it can be shown that the inductance of this model equals I/(r*A)², where r is the radius of the middle of the blades to the centre of rotation, A the surface area of the blades and I the wheel's moment of inertia.--Jocajo (talk) 19:32, 8 February 2013 (UTC)


 * Can this work? If water is forced in one pipe would the wheel turn? Adx (talk) 00:05, 18 May 2022 (UTC)
 * I'd better be clearer: The pictured Hydraulic inductor model blocks the flow completely so can't work, so shouldn't really be used as an example in the article. The principle is good, but is physically unrealisable, guessing this was the source of the original poster's question. Adx (talk) 23:27, 8 November 2022 (UTC)
 * As @Adx mentioned, the image you created was good at getting the point across, but it wouldn't have worked. Incoming water would push on both sides of the paddle wheel, making it not turn at all. I replaced it with a rotary vane pump gif and modified the surrounding text to reflect the change. Pgboswell (talk) 20:35, 3 August 2023 (UTC)
 * I don't think a rotary vane PUMP does the job here. A pump adds energy to the system, making the pressure at the outlet higher than that at the inlet. The TURBINE does the job here, as it will dampen high frequency pressure oscillations (due to the inertia of rotating parts) and reduce pressure at the outlet (depending on the load, which should be small in the analogy in order to represent some parasitic resistance in electricity). I love the new animation of the moving vanes (it can represent both a pump and a turbine), but the text saying that a pump would do the analogy seems wrong to me, only a turbine would. Nicolaufg (talk) 09:46, 26 October 2023 (UTC)
 * @Nicolaufg: Actually, an inductor acts as both a turbine and a pump. When it's being energized, it acts like a turbine, but when it's releasing its energy, it acts as a pump. Many types of turbines cannot act as pumps, but the rotary vane pump can act as both a turbine (spinning up when there is an outside force creating a pressure difference across it) and a pump (using its own energy to create a pressure difference across itself). I agree that "pump" isn't the right word to use here, but I'm not sure what a word would be for something that is intended to act as both a pump and a turbine. Any ideas? Pgboswell (talk) 14:11, 26 October 2023 (UTC)
 * @Pgboswell I still believe it is "just" a turbine what best works here. When you explain a pump here, you mention "using its own energy to create a pressure difference across itself". But equipment known as "pumps" in industry, do not use their "own" energy, they get it from a driver through the shaft. On the other hand, it is common to assume that spinning turbines have inertia and thus they will take some time to spin down. While doing that, the energy they transfer to the fluid is NOT coming from the outside (like in pumps), instead, it was stolen from the fluid when the turbine was spinning up, and it has been temporarily stored as rotating kinetic energy (it is indeed "its own energy"). I think I would simply replace the word "pump" and use "turbine" instead. It is already mentioned that it needs to have a heavy rotor, which is what holds the kinetic energy (inertia), and from an industrial equipment point of view (my field), it makes total sense. Nicolaufg (talk) 16:08, 26 October 2023 (UTC)
 * @Nicolaufg: Ok you've convinced me. I think you're right that turbine is a better word. What image should be shown? The rotary vane pump is a pretty simple image to get the point across. I feel like a picture of a turbine is more difficult to understand. Can you keep the same picture, but instead call it a "rotary vane turbine"? Pgboswell (talk) 17:00, 26 October 2023 (UTC)

Implementation
Has anyone ever tried to implement some logical circuitry with pipes and valves? Just for fun? A hydraulic calculator... --dab (𒁳) 12:44, 4 September 2008 (UTC)


 * I've seen a single hydraulic control valve implement several extremely simple logic gates.
 * I've heard rumors that it is possible to implement any logic gate using fluidics, without any moving parts -- not even hydraulic control valves.
 * I would be fascinated to see a more complex hydraulic device, with the output of one "gate" feeding into the input of the next "gate" ...
 * The closest I've seen so far:


 * MONIAC Computer: apparently worked great.
 * "Heath Robinson Rube Goldberg Computer" "a beast that combines multiple technologies (relays, vacuum tubes, transistors, silicon chips, fluidic, etc.)". Currently under construction?
 * "a CPU fountain": "With a few hundred fluid relays, it’s theoretically possible to construct a simple CPU". theoretical.
 * "The Water-Computer": "a fully-functional, programmable, digital computer that works with a fluid like water, instead of electricity." theoretical.
 * --68.0.124.33 (talk) 05:07, 3 October 2008 (UTC)

drain-pipe theory' by Oliver Heaviside
hydraulic analogy (derisively referred to as the drain-pipe theory by Oliver Heaviside)

hard to beleve a scientist/ mathematician would make this statement.refs rq.Wdl1961 (talk) 15:24, 15 April 2010 (UTC)
 * Heaviside wasn't afraid to call them as he saw them. Paul Nahin wrote a biography of Heaviside that outlined his conflicts with just about everyone. They were a colorful bunch, those 19th century electricians. If I can find my old edition, there may even be that very quotation in it. --Wtshymanski (talk) 21:20, 17 December 2010 (UTC)


 * It needs a reliable source, I've added a citation needed tag. --George100 (talk) 17:35, 23 December 2013 (UTC)
 * Found enough of the Nahin book on Google to see that it was Oliver Lodge, not Heaviside, that called it "drain pipe". Found enough of "Electrical Papers" on line to show that Heaviside was a careful user of hydraulical analogies in very specific cases. --Wtshymanski (talk) 15:54, 12 March 2014 (UTC)


 * I have moved it to a separate second para in the article head. It is off-topic to be the first sentence and may be non-NPOV as phrased. I provided a new first sentence using Mechanical–electrical_analogies as the model, which is terse and to the point.Rick Jelliffe (talk) 03:00, 18 June 2023 (UTC)

Capacitors and rubber walled tank
The analogy for capacitors uses a rubber tank with a rubber diaphragm. What is the rubber lining for? Does the capacator-analogy expand as water enters it when the membrane is totally on one side? It doesn't say that it should be filled with water even when it is "uncharged." The "chargeness" or voltage across it is only how close the membrane is to one side. Slothman32 (talk) 02:19, 20 April 2010 (UTC)


 * use an airfilled steel tank, that will satisfy the differential eq.Wdl1961 (talk) 02:33, 20 April 2010 (UTC)

Only the diaphragm should be rubber. Making the sides rubber implies that the amount of charge (water) in the capacitor changes when it is charged, which is incorrect. Capacitors store pressure/voltage, not charge.
 * Interjection: Capacitors are frequently described as storing charge, as in Q=CV. This is not in conflict with storing energy, just as an elevated tank or dam stores both water and the potential energy of the elevated water.Gwideman (talk) 02:08, 27 September 2011 (UTC)
 * Capacitors are described as storing charge if they're modeled as a simple single electrode, while the second electrode is connected to ground and ignored. If we wish to fully model a capacitor (or employ it in coupling circuits and high-pass filters,) we model it as a two-electrode component where the Q in Q=CV is the time integral of current, i.e. the amount of charge driven into one terminal and out the other. The same is true of batteries regarding ampere-hours, where the charge moves through the battery while none builds up inside. 208.38.200.183 (talk) 15:41, 21 April 2014 (UTC)

Enon continues... The correct term for this piece of plumbing is "hydraulic accumulator" or "pressure accumulator" (though the plumbing ones usually use gas and/or springs). The analogy should not use gas because charge is not similarly compressible in conductors or insulators. Also the bit about polarized capacitors and valves that was in there seems to be nonsense.Enon (talk) 09:42, 24 December 2010 (UTC)
 * If you put enough epicycles in, you can make a geocentric view of the solar system work. But the hydraulic analogy stops being useful very early on; isn't it easier just to learn a few simple *electrical* concepts instead of trying to approximate anything with Rube Goldbert/Heath Robinson kludges? --Wtshymanski (talk) 05:30, 26 December 2010 (UTC)
 * This article is about the hydraulic analogy. Making the analogy more accurate yet less complex and at the same time better referenced in the literature has nothing to do with epicycles. The hydraulic analogy does break down in some circumstances, which are noted in the article, but it is actually very broadly applicable and valuable as a qualitative mental model. Math and "electrical concepts", while themselves valuable analogies, due to their more attenuated relation to physical experience do not provide the same quality of physical intuition of the hydraulic analogy. In other words, better to learn a 90% accurate analogy that can be understood 95% in a few minutes rather than a 95% accurate analogy (pretending to not be an analogy) that can only be understood 50% after 10s of hours (and even then has less explanatory power for such things as why current and voltage have the phase relationships they do in RLC components). Also, having the physical intuition provided by the hydraulic analogy greatly facilitates learning the more accurate and quantitative "electrical concepts" later.Enon (talk) 19:07, 1 February 2011 (UTC)
 * We study the wrong things because it's easier than studying the right things. I would like to read someone's assement of how mcuh the "hydraulic analogy" held back electrical engineering in the early days - you recall, there wsa quite a bit of "resistance" to introduction of alternating current,and I suspect one of the reasons is that by the time you build a hydraulic analogy that acounts for inductance, capacitance, induction, skin effect, and electromagnetic radiation, it's probably easier to just learn the physics and stop analogizing at all. Anyone who's sloooowly charged a fat capacitor through a resistance and watched the voltage creep up, or who's pulled the wires off a choke and watched the current trying to flow even through open space, has a much more accurate physical intuition than all the "drainpipes" can give. And of course when you read that the hydraulic head loss of a pipe is inversely proportional to the fifth power of its internal diameter, all "analogies" with electric circuits go out the window. --Wtshymanski (talk) 17:34, 3 February 2011 (UTC)
 * The hydraulic analogy is inevitably going to have its limits on how much it can demonstrate or explain. Physically intricate concepts, such as skin effect or electromagnetism, will be impossible to explain using the analogy (or very tedious in the least). However, the analogy definitely goes for concepts linking current flow, potential and energy. --Jocajo 19:35, 28 November 2011 (UTC+1)

I have been doing a lot of thinking recently on what would be an accurate model of a capacitor in the hydraulic analogy. Although the idea of a rubber diaphragm works, I do not find it to be very elegant. I myself have come up with two models that could replace it; one similar to the current model and one based on gravity rather than some form of elasticity. Both models, by the way, are mathematically accurate, in the sense that they both correctly predict the amount of energy stored in a capacitor as a function of voltage/pressure, and also how the impedance of a capacitor in an AC circuit is affected by the frequency. I shall post images of these models with calculations within the next few days. --Jocajo 19:44, 28 November 2011 (UTC+1)
 * This is an ok analogy for a capacitor when one terminal of the capacitor is grounded, such as when they're used to smooth voltage supplies. The water tank analog does not work for when a capacitor is used to block DC signals. Maybe the page can present both and explain how each works better for a particular use of capacitors.--98.168.239.210 (talk) 04:57, 21 April 2012 (UTC)

I sometimes think of a capacitor as a cup on a balance, and when there is enough water (electricity) in the cup (capacitor), the cup tips and spills (discharges) the water. — Preceding unsigned comment added by 76.84.16.16 (talk) 04:23, 12 April 2012 (UTC)
 * This would be a model of a relaxation oscillator, not a capacitor by itself. The cup is a capacitor, but the dumping action is not part of the capacitor.--98.168.239.210 (talk) 04:57, 21 April 2012 (UTC)

I hope my rubber diaphragm animation helps. To me it seems plenty a "elegant" analogue. It works on many levels--I wrote a bunch of text here. --Steve (talk) 20:25, 27 April 2012 (UTC)

I hereby propose an alternative to the rubber wall, namely a solid disk seperating the two terminals moved held in place by springs. I have included a picture of it here. The reason I prefer this over the rubber wall model is because it can be used to show the amount of energy stored in a capacitor, and other quantities. This model is mathematically accurate. If we denote the pressure difference across the wall $$P$$, the cross section area of the wall/tank $$A$$ and the stiffness of the springs combined $$k$$ (Hooke's law), then it can now be shown in at least two ways that the "capacitance" equals to $$C=\frac{A^{2}}{k}$$:
 * Alternative for the rubber wall :
 * 1) Reasoning from the observation that, ignoring gravity, any potential energy stored in this system will be stored in the springs. From Hooke's law it is known that this energy is $$E=\frac{1}{2}kx^{2}$$, which can be rewritten as $$E=\frac{1}{2}(\frac{1}{k})F^{2}$$ if we make the substitution $$x=\frac{F}{k}$$ from Hooke's law. Using the definition of pressure, substituting $$F=PA$$ yields $$E=\frac{1}{2}(\frac{1}{k})(PA)^{2}=\frac{1}{2}\frac{A^{2}}{k}P^{2}$$. Considering that voltage corresponds to pressure difference, and that the energy stored in a capacitor is $$E=\frac{1}{2}CV^2$$, we can see that the quantity $$\frac{A^2}{k}$$ indeed corresponds with capacitance.
 * 2) Reasoning from the defining equation for capacitors $$Q=CV$$, where $$Q$$ is the net charge (coulombs) to have passed through the capacitor. Net charge corresponds to displaced volume of liquid, which we will denote $$V$$. We can see that the displaced volume equals the product of the cross section area and displacement in the springs, or $$V=Ax$$. From Hooke's law we have $$x=\frac{F}{k}$$, so $$V=A\frac{F}{k}$$, where $$F$$ is the force on the springs, and $$k$$ the Hooke stiffness of the springs. The force on the springs is created by the pressure difference acting on the plate, so $$F=PA$$, and thus we have $$V=A\frac{PA}{k}$$ or $$V=\frac{A^2}{k}P$$. We see again that the quantity $$\frac{A^2}{k}$$ assumes the same role as the capacitance in the capacitor equation.

What does the expression $$\frac{A^2}{k}$$ tell us? If we make the tank larger by enlarging its cross section area, we increase the capacitance. Also, the stiffer the springs, the smaller the capacitance. Is this what we expected? Yes, because it takes more pressure to push more water through, just like it takes more volts to put more coulombs through a smaller capacitor.

The model assumes the following ideal conditions:
 * The liquid has zero mass.
 * The liquid has an infinitely low viscosity.
 * The liquid is incompressible.
 * There is zero friction between the disk and the walls of the cylinder.
 * The springs stay in the linear operating range.
 * The wall dividing the two halves has zero mass.

The only problem here is that this might constitute 'Original Research', something Wikipedia is not fond of. However, this isn't research in the strict sense that it isn't a conclusion from some sort of data set, but immediately verifiable derivations.--Jocajo (talk) 04:06, 6 February 2013 (UTC)


 * I'm trying to understand the advantage of the springs compared to the rubber (at right).




 * If I understand correctly, you're saying that with the rubber diaphragm, you can't be sure that V=Q/C, i.e. the push-back force is directly proportional to the amount of water flow. Probably V is an increasing function of Q, but who knows if it's exactly linear, it depends on the mechanical properties of the rubber. With the spring, on the other hand, if we assume Hooke's law, V is directly proportional to Q, and even a high-school student can prove it. Is that a correct summary of why you prefer the spring to the rubber? (In my opinion these advantages are real but relatively minor; I think the strength of the hydraulic analogy centers on qualitative aspects, and by the time you're deriving the exact equations, you ought to have already moved on to discussing electrons and voltages ... but again, that's just my opinion) :D --Steve (talk) 03:50, 7 February 2013 (UTC)


 * The main advantage is indeed that, because there is a demonstrable linear proportionality between the push back force of the spring and the displaced volume, the model is true to the behaviour of real capacitors at a deeper level than just concept. The mathematical derivations were mainly to show that the hydraulic analogy goes further than just some superficial similarities, and adds to its mathematical validity as such.--Jocajo (talk) 12:20, 8 February 2013 (UTC)

It's interesting that in some situations, capacitors are analagous to pulsation dampeners (which contain some type of compressible bladder to smooth out flow fluctuations). For instance, a full wave rectifier with smoothing capacitor is a lot like a double-diaphragm pump with pulsation dampener, where the check valves are equivalent to diodes. Tara Zieminek (talk) 20:03, 7 April 2014 (UTC)


 * I like the proposal to replace the rubber barrier by the spring loaded system because it generates equations that teacher could either show students or assign as projects to develop. I wouldn't load down the article with the derivation, but a statement of the solution would be nice.  You could even "hide" the derivation using the template hidden as follows:

Latin nonsense courtesy of the template. You would instead write something like:

...this energy is $$E=\frac{1}{2}kx^{2}$$, which can be rewritten as $$E=\frac{1}{2}(\frac{1}{k})F^{2}$$ if we make the substitution $$x=\frac{F}{k}$$ from Hooke's law...


 * --guyvan52 (talk) 21:05, 7 April 2014 (UTC)

Hydraulic Analogy - Aerodynamics
The "Hydraulic Analogy" is also the name given to the concept of using water channel flows (through a nozzle) to approximate compressible gas (such as air) channel flows. Basically, it allows you to use a "water tunnel" as a cheap wind tunnel by relating the experimental water flow results to a gas flow.

This should probably have it's own page, but I don't know if I will be able to write it. There should definitely be a link to it on this page. I'll look into it, but someone else might want to give it a try. I've never written a wiki page before.

Some references to get started: Buchanan, A., Macartney, R., Thompson, M.C., Brocher, E. & Hourigan, K. (2007) Hydraulic Analogy Study of Supersonic Rectangular-Jet Screech Control with Cylinders, AIAA Journal, 45(7), 1539–1545.

http://www.flair.monash.edu.au/publications/pdfs/BucMacThoBroHou2007_aiaaj.pdf

http://www.mubeta.monash.edu.au/publications/content/PIV09-Kumar.pdf

http://www-personal.umich.edu/~mswool/publications/quantitative_flow_visualization.pdf

Water table design for aero research using he hydraulic analogy: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740003970_1974003970.pdf

http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0658669

Crossalchemist (talk) 00:52, 26 August 2010 (UTC)


 * I have added a confuse tag with a link to the Aircraft Flight Dynamics section. If anyone can find a better reference in Wikipedia, they might add that as well. I have also updated the Analogy_(disambiguation) page. Rick Jelliffe (talk) 03:13, 18 June 2023 (UTC)

Why Lightning is so surprising
It's just occured to me that perhaps the reason properties of lightning are so surprising is the (subconcious or otherwise) attempt to use the hydraulic analogy for electricity - which is particularly misleading when it comes to conceptualizing how lighting travels. Wish I could find a reference for this, because it illustrates a pretty critical limiation of the hydraulic analogy. --Wtshymanski (talk) 21:13, 17 December 2010 (UTC)
 * Lightning is not so surprising if we properly view it as a *change* in conductivity, where insulator (a fluid barrier) is converted into conductor (a circuit path.) The hydraulic analogy would be the growth of a fracture through a very thick pipe wall, i.e. the solid being converted from a barrier to a passage.  And fractures in solids even display the dendritic branching behavior of lightning.  Of course to be complete, the fracture would have to convert some of the substance of the pipe into a liquid, as if the tip of a growing fracture in a block of ice could produce some meltwater which fills the fracture. 208.38.200.183 (talk) 15:05, 21 April 2014 (UTC)

Leaking pipes
I largely rewrote this paragraph. The possibility of "if a hole is made, the water can pour out" has nothing to do with inapplicability of Kirchhoff's current law (I guessed it was that the original author tried to explain). First of all, the analogy relies on volume (because pressure=energy/volume), not mass or other conserving quantity. An analogy to the Kirchhoff's current law should imply that the volume of the liquid is constant, even locally constant. This is possible with some clauses, but IMHO has little practical importance. First, the liquid must be incompressible. Second, the system should be enclosed in a hard envelope, such that its volume become constant. Third, this volume must be entirely filled with incompressible liquid. Then we may have the Kirchhoff's current law. And this does not mean that there are no leaks. This means that there are no exchange of substances with the outer environment, either by leaks or by moving parts such as pistons. Because this explanation is quite long, I wrote in short, why Kirchhoff's current law does not hold and removed all irrelevant reasonings. Incnis Mrsi (talk) 18:55, 19 February 2012 (UTC)


 * There is no need to say that Kirchhoff's laws hold always in every hydraulic circumstance, or don't. I think the purpose of the article is served by showing just one hydraulic situation in which it holds, so that people can understand why it might be true for circuits. Therefore I put an example in the article with a picture of a copper tee and a description of how water flows equally into and out of it. --Steve (talk) 20:25, 27 April 2012 (UTC)

Hydraulics vs Pneumatics
I have the feeling that pneumatics may be a better analogy because acoustics are more pronounced. Altho the analogy is still flawed, acoustics remind me of how potential travels through electric cirquits. It is usefull for explaining stuff like reflections on signal lines and decoupling capacitors. — Preceding unsigned comment added by 83.87.238.229 (talk) 16:03, 12 March 2013 (UTC)

I like this article
After seeing all the complaints about this article, I would like to endorse it. Analogies are not only useful for understanding electricity, but also for analyzing similar systems (such as sound waves in a muffler). It is not important which analogy is used, once the reader understands that analogies are possible, it all becomes quite transparent. I like the way editors have placed alternatives in the talk page, instead of cluttering the main article with an endless list of analogies. One reason it's hard to find literature that supports analogies is that the concept is a bit "shallow" for publication. They are useful for an electrical engineer who wishes to dabble with acoustics. If this dabbling leads to anything publishable, it is easy to translate the analog equations into proper physics equations using conventional variables (e.g,, pressure instead of "pseudovoltage").--guyvan52 (talk) 16:20, 11 March 2014 (UTC)
 * In my effort to reformat, I had to use two galleries because a rather large laptop screen failed to display five images side by side. I also condensed the discussion of the voltage source/ current source into one section because the previous version went a bit too far into the different types of hydraulic pumps.  Also, I experimented with putting all the images to the right in the conventional way, but the result was a large gap after the prose ended and the images did not line up with the prose.  I am not sure what the best practices for multiple images in situations like this, but if there is a policy I would be happy to implement.--guyvan52 (talk) 15:44, 12 March 2014 (UTC)
 * I do like the article too. I am a Chemical and Process Engineer and now interested in Electronics as a hobby (home automation, simple robotics, etc). My brain works with hydraulics, and I had a bit of a hard time to "intuitively see" the effect of placing a capacitor or an inductor in a line. This article really made it clear to me. Nicolaufg (talk) 09:57, 26 October 2023 (UTC)

Duplicate figure?


Is the figure to the left a unnecessary duplicate of the one to the right?--guyvan52 (talk) 22:12, 12 March 2014 (UTC)

O. Heaviside derision?
Might the opening sentence be a bit misleading? We could instead find a quote from a promoter rather than a detractor. Heaviside, Fitzgerald, Hertz and Lodge worked together on and off during 1878-1902 to flesh out JC Maxwell's work. Lodge developed many mechanical and fluid analogies of currents and fields for use in his electrical lectures. He originated most of today's hydraulic analogy, building on JC Maxwell's concept of conductors containing a charge-fluid which was incompressible. For example, see his capacitor analogy, a water-filled sphere divided by a thin rubber membrane (a balloon,) 0. Lodge "Modern views of electricity" p178 London:MacMillan 1889, described in "The Maxwellians", BJ Hunt 1991 Cornell U. Press. — Preceding unsigned comment added by 208.38.200.183 (talk) 15:19, 21 April 2014 (UTC)

Historical reason
Electricity was thought to be a liquid, when was first discovered, and was described as such for years later. Perhaps it is the historical reason behind this analogy, besides the intuition, for understanding the behaviour of something invisible. The same goes for the glossery used for electricity - the word "current" (flow) comes from the analogy to water. Galzigler (talk) 14:47, 23 September 2016 (UTC)

Attracting electrons?
I have the impression this sentence is wrong: "Also, an accelerating electron will drag its neighbors along while attracting them, both because of magnetic forces."

Shouldn't it be: "Also, an accelerating electron will push its neighbors along while repelling them, both because of magnetic forces"? --91.34.131.163 (talk) 18:29, 20 October 2016 (UTC)


 * No, I think that is right. Two like charges travelling in the same parallel direction will have magnetic fields that cause attraction perpendicular to the direction of travel.  Each moving electron behaves as a small magnetic dipole.  The effect of an accelerating charge starting an acceleration is other nearby charges is the electromagnetic equivalent of linear frame dragging from general relativity and is in the same direction. It would be nice to have a source reference for that though. SpinningSpark 19:15, 20 October 2016 (UTC)

Original Research template tag
I've have removed the original research warning template, it being 5-years-old and seems not reflective of the current article. If it is really important to you, object below. Nuvigil (talk) 14:40, 13 June 2017 (UTC)

Lede out of specs. + Tone
Please bring up to specs, see: MOS:LEAD: "The lead serves both as an introduction to the article and as a summary of its most important aspects.  The lead should be able to stand alone as a concise overview of the article. It should define the topic, establish context, explain why the subject is interesting or notable, and summarize the most important points—including any prominent controversies. The emphasis given to material in the lead should roughly reflect its importance to the topic," My emphasis.

Further, the lead, in tone, seems destructive to the analogy by starting with derision and warnings. ...Is starting negatively a good way to teach a complex concept? I think somebody needs to actually try to fully communicate this highly useful heuristic first. Also I don't think the assumption that this is "THE hydrolic analogy" can be supported. There must be hundreds.  — Preceding unsigned comment added by 2602:306:CFCE:1EE0:E454:D78D:E92F:E1E6 (talk) 05:19, 30 April 2019 (UTC)


 * Changed lede to analogies. Electrical-Mechanical has uses the plural too. Rick Jelliffe (talk) 04:11, 18 June 2023 (UTC)

Proposed new Lede section
I think the lede section is so far off base it needs a major re-write. See: MOS:LEAD

"The lead section (also known as the introduction, lead, or lede of a Wikipedia article is the section before the table of contents and the first heading. The lead serves both as an introduction to the article and as a summary of its most important aspects.

"The lead should be able to stand alone as a concise overview of the article.  It should define the topic, establish context, explain why the subject is interesting or notable, and summarize the most important points...."

It's notable as an extremely useful and unique introductory electronics teaching aid. Perhaps the main use of these analogies are to give Joe Average a basic feel for electricity, like what's the difference between voltage and current? What's current? And there is no "one" or two analogies as implied, there must be hundreds, invented on the spot by technicians every time she is asked...hundreds, all in agreement with those here. This is not the stiff rocket science this article implies. For example, take this quote: "the various electronic components are represented by hydraulic equivalents," as if the user now needs to memorize which "hydraulic equivalents" match "THE various electronic components." No. Loosen up, to: "many various electronic components can be represented by hydraulic equivalents." For example voltage, current, induction, work, resistor, some Ohm's law, can also be illustrated with just a garden faucet, hose & nozzle. These are analogies, learning aids, not rules.

And this opinion? "As with all analogies, it demands an intuitive and competent understanding of the baseline paradigms (electronics and hydraulics)." 1.: Oh really? 2.:"paradigms?" Just what Joe Average needs, a long education in philosophy of science. Lets just hope he doesn't follow that link to get an idea what current and voltage are.

So if Joe Briefcase comes here asking; "What's current? (I have 5 - 10 minutes.)" this article is utterly counterproductive. He may as well take a class.

More technically; I also complain that here we seem to have a mere model, and a case of "misplaced concreteness," as if the analogy or model was actually a real thing. "The fallacy of misplaced concreteness...refers to the error of mistaking the abstract for the concrete." If carried to extreme, the model (since it aint the real actual thing) ends up with more patches and mental gymnastics than useful theory or model. (Economists will know EXACTLY what I'm talking about.)

I propose we treat this analogy primarily like a highly valuable (a RARE thing!) teaching tool that Wikipedia show-offs can ruin. Once that has been explained, perhaps in the lede, for the "general user," more confusing advanced electronics and detail such as our derisive Victorian Oliver Lodge, can be explained. (But seriously, what would somebody with advanced electronic knowledge be doing here?)

The article says: The electronic–hydraulic analogy (derisively referred to as the drain-pipe theory by Oliver Lodge) is the most widely used analogy for "electron fluid" in a metal conductor. Since electric current is invisible and the processes at play in electronics are often difficult to demonstrate, the various electronic components are represented by hydraulic equivalents. Electricity (as well as heat) was originally understood to be a kind of fluid, and the names of certain electric quantities (such as current) are derived from hydraulic equivalents. As with all analogies, it demands an intuitive and competent understanding of the baseline paradigms (electronics and hydraulics).

New Section: Paradigms  There is no unique paradigm for establishing this analogy. Two paradigms can be used to introduce the concept to students using pressure induced by gravity or by pumps.

In the version with pressure induced by gravity,...

Rather, I propose something like this: An electronic–hydraulic analogy (or an electricity-waterpipe metaphor) are very widely used analogies to quickly explain some basic concepts of electricity and basic electronics such as voltage, current (Amperes), resistance, and even more advanced concepts such as capacitors, inductance, and how transistors and amplifiers work. The analogy is a good one because an "electron fluid" or electric current flowing in a circuit often have strong similarities to a flowing water current in a hose or pipe. Since electric current is invisible and the processes at play in electronics are often difficult to demonstrate, the various electronic components are represented by hydraulic equivalents such as water nozzles, valves, water pumps, water towers, paddle wheels for doing work, and so forth. Indeed, electricity and heat were originally understood to be fluids, and the names of certain electric terms and concepts like current, are hydraulic.

New Section: Some Useful Specific Analogies  All working circuits (such as a flashlight or radio) have conductors, voltage, current, and resistance. By definition, a working circuit has flow. Think of water flow. Think of water pipes as the wires or conductors, pressure or pounds per square inch as voltage, think of quantity of flow such as gallons per minute as current (Amps), and a partially closed valve or friction acting as resistance (Ohms). To complete our circuit we need a source of power to pressurize and move our current. This might be pressure induced by gravity or by water pumps. In the version with pressure induced by gravity,...

[Now, not later we jump to relevance: how cool and elegant all this might be:]

In working electric circuits there are definite relationships among voltage, current, and resistance, such as the highly useful "Ohm's Law" formula. In working hydraulic circuits, there are similar relationships. In a garden hose, if you increase the resistance by closing the nozzle, the pressure in the hose goes up and the gallons per minute goes down. Same in our working electric circuit; if you increase the resistance (Ohms), then the voltage (volts) goes up, and the current (Amps) goes down IN EXACT PROPORTION to each other.

That's the idea. I think all of that and a little more would make a nice lede. The garden hose analogy is cool because we can get a meaty payoff without going into power source. (Slam the faucet open and shut and watch the coiled hose jump, analogy to inductive reactance, coils resisting current change.) KISS them first.

A common Wikipedia mistake is to still write for teacher who judges nice for 100% lack of error (NOT a worthy goal here) and trivial details (to prove you read the chapter,) rather than to educate curious Joe Lunchbox with a few minutes to spare, who only cares about getting an overview concept he'll find useful. I'd do it, but I'm not signed up. Feel free to copy paste.

Other than that basic easy-peasy stuff for the lede or intro for Average Joe, I'll not complain about the rest of the more formal article except to to give a definition: Definition of "equivalent" 1 : equal in force, amount, or value also : equal in area or volume but not superposable a square equivalent to a triangle 2a : like in signification or import b : having logical equivalence equivalent statements 3 : corresponding or virtually identical especially in effect or function

I think in some of its 22 usages, "similar to," "relates to," or "is analogous to," might be a more clear fit. 

Add electronic analogy of a waterfall
Mention what the electronic analogy of a waterfall is. Jidanni (talk) 00:27, 1 March 2020 (UTC)

Add the hydraulic analogy of a short circuit
Mention what would be the hydraulic analogy of a short circuit. Jidanni (talk) 00:45, 1 March 2020 (UTC)

Add lots of analogies
Perhaps go into various lists of hydrology features, finding ones to add electrical analogies of which to this article. Probably some don't have analogies, but probably many do. Jidanni (talk) 06:26, 1 March 2020 (UTC)
 * Flood, Dam, Confluence, Stream capture, Fluvial processes
 * Category:Hydrology
 * Category:Bodies of water
 * Category:Hydraulic structures
 * Category:Fluvial landforms

Darcy-Weisbach equation
It would be better for this article to remove the sloppy and nonsensical statement "Resistance in most electrical conductors is a linear function [maybe the anonymous author meant: "constant"?; 2012]: as current increases, voltage drop increases proportionally (Ohm's Law). Liquid resistance in pipes is not linear with volume, varying as the square of volumetric flow (see Darcy–Weisbach equation)." In contrast to what the statement suggests, the Darcy-Weisbach equation article says that the resistance is constant for laminar flow. It reduces to the Poiseuille equation. If there are no objections I would like to remove the statement within a few days. Ceinturion (talk) 09:59, 3 April 2021 (UTC)
 * Done Ceinturion (talk) 18:03, 6 April 2021 (UTC)

Where is the water pipe analogy ?
People come here looking for the water pipe analogy that most people are familiar with that explains current, voltage, etc. It's not here. The intro implies that it is. Derwos (talk) 22:36, 3 February 2022 (UTC)

Engineering Equations?
Obviously missing are the equations that model phenomenon. The differential equations from linear systems and the equations based on the Naperian constant 'e'.

Inductors, capacitors and filter networks common to electronic engineering circuits, especially direct current (d.c.) circuits are not presented.

The analogy with d.c. circuits is simplest and easiest to understand and use. 166.198.161.67 (talk) 17:52, 13 January 2023 (UTC)

This my post. I'm adding a mention of banging water pipes in plumbing Jimlynnjulian (talk) 18:13, 13 January 2023 (UTC)