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Is there an electron 'water hammer' effect?

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Full Member level 3
Sep 25, 2005
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electric water hammer

I frequently see relationships in electronics explained as water in a plumbing system and was wondering; is there an effect with electric currents similiar to the water hammer effect in a plumbing system?

To explain; all mass has inertia. If water is flowing in a pipe the water has a certain inertial moment behind it depending on how much water is moving, and how long the pipe is. If the tap is suddenly closed very fast the energy from the inertia that mass had is transfered as various waves of dramatically increased presure inside the system. The only equivilent electrical effect I can relate this to would be inductance, such as the large voltage inductive loads can generate when the current stops (magnetic field collapses)

Can anyone shed more light on this comparison between molecular and atomic systems? Just from what I've discussed so far I see an almost direct correlation between a molecules's inertial gravitic moment compared to an electron's inertial magnetic moment.

The more I learn about electronics and how they actually work the more I'm curious about the links they have with larger scale systems and their inter-relation. I would like to know more of what the users of this forum think and have to add to what I've said from the wisdom they've collected over the years.

P.S. Please keep the hard math out of this thread. I would like users thoughts and words in an intuative sense, not a purely mathmatical one. Meaning, please only relate words to constants, never to equations, especially derived ones.

hammering effect on gas field

The water to electron analogy falls apart when you look at what really happens on the atomic level.

First - electrons don't really 'flow' like water molecules. If you could paint an electron red and watch it, you would see that it meanders in a rather irregular path through the crystal structure of the conductor. The 'current' in an electrical circuit is really the influence of one electron upon another - it is the EFFECT of the electron that moves through the circuit. Look at it as a bunch of people standing closely together in a line - if you shove the one in front of you, he bumps into the guy in front of him, who then bumps into the guy in front of him, and so on. Finally, the guy in the front of the line gets bumped - everybody is still in the same place in line, but the last guy in line caused the first guy in line to spill his beer by shoving.

What 'flows' in an electic circuit is the field effect of one electron upon another. The energy isn't transfered by electron mass, but by electron fields. It is that bit of physics that allows electrical current to 'flow' at near light speed in our circuits - energy, not mass, is what is moving. It is true that electrons come and go from the ends of a conductor connected to a battery; however, any given electron doesn't make the whole trip in a straight line, and some don't make the trip at all (they just shove from their place in the line) - the field effect of the electron is what makes the straight end-to-end trip. There is no inertia of the electron field 'flow' (it isn't mass) - hence, no 'electron hammer'. You can cut off the 'flow' of electric current as rapidly as you like, and the wire will never burst from the kinetic energy and inertia of the electron 'flow' - there isn't any.

current reports of the water hammer effect

What is the electron flow analogy of the brawl that ensues following the spilt beer?


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kinetic energy electron circuit physics forums

An electron has mass, very small but it has one, so it must follow all the laws that a mass has.
I never said the energy was the flow of matter itself, just it's magnetic/gravitic moment equivilent. On a molecular level a 400 foot pipe might have an equivilant effect as a Henries worth of current flow in a conductor. There is most definitly a direct relation. As you say people bumping into each other is more like how electrons move, however this is exactly how presure waves in molecular (water) system move.

electricity effect in hammer

Remember that velocity is a vector quantity - it has direction and magnitude. The direction is the key here.

What you are missing is that the water molecules actually are moving at the flow velocity in the direction of the pipe plane. If you put dye in the water, it actually moves at flow velocity from one end of the pipe to the other. This is not a field effect - it is actual movement of molecules in a given direction at a specific speed.

Electrons are not moving at the velocity of the electric current in the wire plane. The electrons move in all directions throughout the crystaline structure of the metal - the movement has been described as a 'swarm' or 'cloud'. It is that movement in virtually all planes that gives the electons, as a collective mass, a zero group velocity when averaged through the entire circuit - at most you could consider it as a drift, rather than a flow of mass. The electron "flow" is really the movement of a massless electromagnetic field in the vector direction of the wire. It is the group velocity of the electromagetic field that defines the electric "current" - not the group velocity of the mass of electrons.

water hammer inductance

I built a pulsed power supply a few years ago for Plasma Ion Implantation.

The pulses were 60kV at about 1400 Amps. The leads to the plasma chamber
were 20 parallel conductors, triple 0 gauge. The leads were about ten feet
long, and suspended above the floor.

The system rep rate was 16 PPS, and the cables danced around like a snake
having sex!

If that isn't the 'water hammer effect', I don't know what is!

At 1400amps with parallel cables, I would expect some very strong magnetic field interactions between the cables - and with any ferrous building materials within several feet. The dancing was undoubtedly due to the intense magnetic fields you created.

Remember - it is the di/dt that gives rise to the fields, and you were pulsing some impressive current through those conductors.

The graphical analysis method of pulses on a transmission line with mismatched and nonlinear nodes uses the same procedure as water hammer analysis. In fact, the method is named after Bergeron who devised the graphical method for hydraulics.

flatulent said:
The graphical analysis method of pulses on a transmission line with mismatched and nonlinear nodes uses the same procedure as water hammer analysis. In fact, the method is named after Bergeron who devised the graphical method for hydraulics.


It is only a mathematical method for evaluating non-linear circuits that happens to work well in both worlds. There is no similarity in the physics, only a similarity in the mathematics.

If there's a similarity in mathmatics then that means the physical systems must be related in some manner. I don't mean directly IE molecule for electron or any other such direct connection. But it does say a lot when you can use the same equations for two fundamentally different systems and they both produce useable results.

Sceadwian said:
If there's a similarity in mathmatics then that means the physical systems must be related in some manner. I don't mean directly IE molecule for electron or any other such direct connection. But it does say a lot when you can use the same equations for two fundamentally different systems and they both produce useable results.

How in the world can you make a logical leap like that?

Using your logic would mean there is a physical relationship between sound waves in a membrane, nuclear particle diffusion at the boundaries of a nuclear reactor, and electromagnetic fields in a circular waveguide because they all can be described with Bessel Functions.

Simply because a mathematical technique can be applied to solve the variables in a problem does not imply in any way that the things being analyzed have the same, or similar, physical properties. What it does say, is that we tend to use the mathematical models that are familiar to us in describing the world.

Just because a dog has four legs and a chair has four legs does not mean there is any physical relationship between the two. (Except, perhaps, that the dog is always in my favorite chair when I want to use it.)

Actually there is a direct relationship between a dog and a chair. They're both excelent designs for stablity, that's why they both have four legs. The function the legs on a dog have and the legs on a chair have are fundamentally the same, that's all I'm saying, not a direct physical relationship but definitly a functional one.

In most of cases the analogy of water hammer efect and effect of an electron in a solid is not valid. Most of time the average speed of electron in a solid is omparable to mm/s or cm/s. At a speed of that range the effect of termal motion of electrons is the dominant one, and the current flow is just a drift of electrons that flow chaoticaly inside of metal.

But (there is allways a but in some explaination), in cases of extremely fast switching devices, as it is case with the modern semiconductors in a computer parts or high current high energy switching devices, the effects are drastic. In very fast switching transistors, the leads at the source drain and gate of the transistors are verry small (because of minimization of parasitic capacitance and so on...). A frend of mine is in a field of solid state physics, and I have seen the SEM images of the gates. Even at so low voltages (2.5V - 3.3V) because of the fast switching rate and als large electric fields, the electrons are accelerated to a very large energies comparable with approx 257K [room temperature]. If we consider that the voltage diference between the source and drain is 2.5V and the method of producing such transistors is to implant several atoms as a gate, it is easy to imagine that on such small distances electron woud have only several colision in the path -> energy of an electron is comparable with 1eV => 11500 K. So single electrons have a large energies and they could make a verry large impact on the electrode.

On the other hand, in the case of gas discharge, the mean average energy of the electron is very large. For a normal plasma discharge temperatures, also the electron energies are comparable with 1eV or in case of some more hotter plasmas it coud be realy experimentaly achieved even several dozens, and in few places on earth several hundreds of eV. I hope that if You have finishe anny course of gas discharge physics or electronics, You coud rememger the effect of sputtering of the cathode. It is related to the high electron energies. As a most extreme discharge device, that is used as a extremley fast high voltage switch, lets imagine that we have to swith the capacitor of 1uF on 10kV => 10^-2 Coulombs = 10mC, and a pseudospark is designed to have the distance between the main electrodes much smaller than the free path of an electron in a buffer gas. It means that, in average, every electron that flows thru that device poses the impact energy insignificantly smaller than the charge of electron multiplied by the voltage on electrodes. That means thet first group of electron have the enrgy of 10keV = 10000eV, while the las ones have couple tens of electron volts at which the process stops.

So there exist thje efect of "electron hammer" but not in normal conductors at normal conditions (even several kA).

Sincerely Your

Nenad Sakan

Just another thought - Water hammer effect occurs as the fluid flow gets a sudden change. Any slower change d/dt reduces the hammer effect.
In electronics, nature does not allow us/anything to stop the electron motion in a way we stop water flow from the bathroom shower - the natural phenomena well described in Physics as inductance of any conducting path which resists and d/dt change in current value - there is nothing in nature having finite conductivity but zero inductance.

Maybe one more thing, that we watch inside microchip interconnects especially with Al processes - "ELECTROMIGRATION" - where electrons, with their finite mass - behaves somewhat like fluid movement - and they move metal atoms in their direction - it will be good research topic to study "Water hammer Effect" with "Electromigration" together.

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