2017-08-04 09:10:09 UTC
"The Formation of the Floating Water Bridge including electric breakdowns"
"Taking some more time to watch the bridge in action, one is stupefied by the complexity. The water movement is bidirectional, i.e., it simultaneously flows in both directions..."
"One thing that the researchers did notice is that the water in the bridge tends to get quite hot as the bridge forms – in some cases exceeding 50 degrees Celsius (122 degrees Fahrenheit). According to Benmore, there have been cases in which boiling floating water bridges have formed."
Floating water bridge / thermography
The floating water bridge is a relatively complicated system - it would be difficult to extract the underlying fundamental physics from it. Fortunately, the same fundamental physics is present in the much simpler capacitor-in-dielectric-liquid system.
In the electric field between two capacitor plates (or, generally, two opposite electric charges) water develops a specific force (pressure) which, like other forces, can cause motion and produce work:
"However, in experiments in which a capacitor is submerged in a dielectric liquid the force per unit area exerted by one plate on another is observed to decrease... [...] This apparent paradox can be explained by taking into account the difference in liquid pressure in the field filled space between the plates and the field free region outside the capacitor."
Wolfgang K. H. Panofsky, Melba Phillips, Classical Electricity and Magnetism, pp.115-116: "Thus the decrease in force that is experienced between two charges when they are immersed in a dielectric liquid can be understood only by considering the effect of the PRESSURE OF THE LIQUID ON THE CHARGES themselves."
Tai Chow, Introduction to Electromagnetic Theory: A Modern Perspective, p. 267: "The strictly electric forces between charges on the conductors are not influenced by the presence of the dielectric medium. The medium is polarized, however, and the interaction of the electric field with the polarized medium results in an INCREASED FLUID PRESSURE ON THE CONDUCTORS that reduces the net forces acting on them."
Crucial questions are: If the pressure that emerges between the plates is allowed to produce work, what source of energy will be used? And what molecular mechanisms will be responsible for the work production? I tried to answer such questions in 2004 but the paper was not very well written:
Biased Thermal Motion and the Second Law of Thermodynamics (August 12, 2004)
Let me offer a clearer (I believe) explanation. Consider a constant-charge parallel-plate capacitor with a polarized SOLID dielectric between the plates:
Since the molecules of the dielectric material are polarized, they generate an electric field which counteracts the original field and so reduces the voltage between the plates. On the other hand, the attraction between the plates increases (the polarization obviously reinforces the original attraction).
If the dielectric is LIQUID and the plates are totally immersed in it, the attraction between the plates surprisingly decreases, due to the pressure that emerges in the space between the plates. We have a high pressure between the plates and a lower pressure outside the capacitor so if we punch a small hole in one of the plates, there will be an ETERNAL FLOW through the hole, from inside (between the plates) to outside. In other words, we will have a SYSTEM IN DYNAMIC EQUILIBRIUM. The eternal flow can be harnessed to do work, in violation of the second law of thermodynamics.
The system can violate the second law in a more traditional way. If the plates of the capacitor are only partially immersed, the pressure between them pushes the liquid upwards:
I. Brevik, Fluids in electric and magnetic fields: Pressure variation and stability, Can. J . Phys. (1982): "Fig. 1. Two charged condenser plates partly immersed in a dielectric liquid. [...] Fig. 2. The hydrostatic pressure variation from point 1 to point 5 in Fig. 1."
Rise in Liquid Level Between Plates of a Capacitor
Liquid Dielectric Capacitor
Chapter 11.6.2: Force on a liquid dielectric
But the rising dielectric liquid can do useful work, e.g. by lifting some floating weight, and here is the crucial question again: At the expense of what energy is the work done? Since, by switching the field on and off, we do no work on the system, the energy supplier can only be the ambient heat. That is, the system can cyclically lift floating weights at the expense of heat absorbed from the surroundings, in violation of the second law of thermodynamics.
What is the molecular mechanism behind the effect? Here is a schematic presentation of water dipoles in the electrical field:
If it were not for the indicated (with an arrow) dipole, other dipoles in the picture are perfectly polarized as if there were no thermal motion. Of course, this is an oversimplification – thermal motion is a factor which constantly disturbs the polarization order. However the crucial point is that, as can be inferred from the picture, any thermal disturbance contributes to the creation of a pressure between the plates. Consider the indicated dipole. It has just received a strong thermal stroke and undergone rotation. As a result, it pushes adjacent dipoles electrostatically, towards the plates. Macroscopically, the sum of all such disturbances is expressed as a pressure exerted on the plates. One can also say, somewhat roughly, that the indicated dipole has absorbed heat and now, by pushing adjacent dipoles, is trying to convert it into work.
In general terms, electric fields manage to channel the chaotic thermal motion into a macroscopically expressed force capable of doing macroscopic work. In 2002 I tried, for the first time, to call the attention of the scientific community to the effect (but failed):
"In the chemical example, dynamical equilibrium is established in the presence of catalysts that selectively favor either the forward or reverse reaction - a property that is by no means indisputable. (Rather, the denial of this property is an essential dogma in chemistry). Yet there is another example in which the principle of dynamical equilibrium is, in my view, obvious. [...] ...as two vertical constant-charge capacitor plates partially dip into a pool of a liquid dielectric (e.g. water), the liquid between them rises high above the surface of the rest of the liquid in the pool. Evidently, if one punches a macroscopic hole in one of the plates, nothing could prevent the liquid between the plates from leaking out through the hole and generating an eternal waterfall outside the capacitor. This hypothesis has been discussed on many occasions but so far no serious counter-argument has been raised." Pentcho Valev, The Law of Self-Acting Machines and Irreversible Processes with Reversible Replicas. http://adsabs.harvard.edu/abs/2002AIPC..643..430V
Other scientists have also seen the analogy between the capacitor-in-dielectric-liquid system and the floating water bridge:
A. Widom, Y.N. Srivastava, J. Swain, S. Sivasubramanian, Maxwell Tension Supports the Water Bridge https://arxiv.org/ftp/arxiv/papers/0812/0812.4845.pdf