Strange effect!

[tinu]

Actually, if you suspend the electrodes of the cell in the water by the power cables themselves (hanging from vertical), so that none of the cell?s parts is in physical contact with the walls of the glass or with its bottom (but electrodes still completely submerged), then those effects due to the cables should be at least significantly minimized. If the cable length from the ?hanging point? to the water level is short enough, I hope that the consequences of wire dilatation will fall under the available weighting resolution.
   
It may very well be due to thermal effects after all, judging by the second graph. Almost linear increase (a good approximation for dilatation) followed by an exponential decrease, due to the cooling (caloric exchange with the environment).
My initial hypothesis (magnetic interaction) is clearly not of prime importance. That?s obvious. If it was, that exponential fall after cutting power off wouldn?t be there. Thermal effects fit the picture much better. (And I apologize for questioning it, as you clearly dismissed magnetism at the end of the first post; at a first glance, without zooming in, the fall seemed pretty instantaneous to me, as seen on the first graph)

Hope it helps.
If not, please post more, eventually about the cell itself as well as others details of the setup, as you may consider relevant.

Tx,
Tinu

P.S. Using a full ?on the balance setup? is actually not a bad idea at all. Not because the source may not be good enough but because it would eliminate from start the main thermal dilatation effects. A small rechargeable 9V may provide for a short time enough voltage (although at low current) at a relatively small added weight. It would not be much of an issue that voltage and current will remain un-recorded. (Both can be measured in advance and their exact value is not of concern here). But the small pain in the ? (technically speaking) would be, imho, to switch the cell on-off remotely, without really disturbing the balance.
Assume that, indeed, a weight increase will be felt in the above case. Now, that would be meaning one hard& long head scratching! Almost can?t wait the final outcome.

[HTwoGo]

My original plan was to run the sealed cell (with a small water air lock) to evolve a set mass of water/gas and then look at the power absorbed, to get a look at the efficiency. Sealed to mitigate evaporation, (I can easily see evaporation of water on the balance on an uncovered vessel) air lock to trap the mist of, probably hydrogen filled water bubbles, again to mitigate unknown losses. To have the electrodes dipping into the electrolyte adds the following problem as I see it, the electrode will have perceived flotation in the electrolyte proportional to the volume of displaced electrolyte, this will vary as the gas is evolved and the density of the liquid changes, the electrodes will see some buoyancy from bubble adhesion, and the changing volume will add further unknowns, to add a gaiter or other diaphragm to contain the unknown electrolyte losses with dipping electrodes, the gaiter must see no pressure differential or the errors will be massive.

The fully autonomous cell is beyond my budgets at the moment but I can?t see how I would get the power resolution I need for in my tiny cell, to date most of the rig has been existing kit.
I will post some existing and propose pictures tomorrow.

When you talk of thermal dilatation effects I assume this is the whole conductor over current thing with gross degradation of the wire?

Best, HTwoGo

[tinu]

Well, floatation is the second candidate to the strange effect after thermal. I?ll explain myself, mainly for all readers; I assume you are familiar with it, HTwoGo.

Contrarily to any common sense, floatation of electrodes might lead to an increase in the weight of the cell.
Here it is a simple experiment in supporting the above, experiment that can be checked with almost any balance. Take a glass with some water. It will weight one value. Put your finger in the water, without touching the glass. You?ll see then the glass weights more. Why? Because due to floatation (Archimedes), your finger is pushed up. But due to Pascal and Newton 2nd, this force is transmitted through the water to the bottom of the glass, being felt as a supplementary pressure, measured by the balance as a supplementary weight.

I come back: Assuming that part of the electrodes weight is supported by the power cables and, through them, further supported by /transferred to the external setup, this part of the weight is not initially recorded by the balance. When electrolysis begins, due to the bubbles attached to the electrodes, a fraction of that part of the weight is no longer supported by the wires (and by the external setup) but is supported by the bubbles and further transferred to the balance, as per above-paragraph explanation. Hence, bubbles start to form -> balance starts indicating a weight increase.

I still have to figure out how to overcome this without all on-the-balance setup. I also can?t be 100% sure of the above, never done that except the first experiment with a common balance, but at least that?s physics say it should happen.

Pls comment,

Tinu

P.S. Also, I apologize for my limited English. If I was confusing, please indicate in which part.

[tinu]

I forgot to respond to:

When you talk of thermal dilatation effects I assume this is the whole conductor over current thing with gross degradation of the wire?

I understand that wires are relatively thin and flexible.
By thermal dilatation effects, I had in mind the following:
- a slight increase in length, linear with increase in temperature, both for the metal inside (cooper, I assume) and for the insulator;
- a decrease in stiffness (a relaxation) with an increase in temperature, probably more pronounced for the insulator (but I don?t know how this can be mathematically described). Also here can be included a tendency of the wires to curve themselves (a memory effect) in the absence of outside forces but when the temperature increases.

The above should manifest over the entire length of the cables, although only partially will be felt by the balance.
I don?t understand well ?gross degradation?. If necessary, please detail. What I can tell is that I assume the thermal effects are pretty much reversible and they do not permanently affect the wires.

I assume that the second line above may affect some experiments significantly more than the first.
Anyway, stiffness is to be manifested only if the wires are curved and, if by modification of their curvature, they will transmit supplementary forces to the balance. Therefore, in the ?hanging-by-wires? setup I proposed, stiffness should not be a concern.
And I assume also that because of the insulator, the increase in length with temperature is very small. Also this would be an advantage for the proposed hanging setup.

The other factor of main concern in the hanging setup would remain floatation. If effects are close to zero - > thermal is the cause. If effects are even more pronounced - > floatation is the candidate.

Tinu

[HTwoGo]

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