Is water an ohmic conductor?

[effectivedragon]

In recent days I have done a few experiments measuring the current of water as it goes up from 9 volts up to 36 volts, and following Ohms law to convert it to resistance. And I discovered a very interesting trend. In between 9 and 18 volts, there is a massive drop in resistance (by around a 40% reduction) but then as I go up to 27 volts, its a 5% reduction, and is even less of a reduction when reaching 36 volts. I've done this experiment a few times and this has continued to happen. This is it visualised on a graph;

I am curious to know why this happens, why there seems to be a reduction as I go from 9 to 18 volts, yet the reduction seems to reduce at 27 volts and reduce further at 36. Is there a reason that? And as I go further up the voltages (don't want to test with higher), does this continue with the reduction in resistance continuously reducing, and if not at what voltage does it change?

Specifically am asking why this is happening and what happens when the voltage gets higher. I kinda want to know what resistance can I expect at around 240 volts

In the following video, a YouTuber does this experiment through a plastic pipe and tested AC through water (and also did DC in another video) and the results other than the early voltages (which lends credence to my theory about it being calculations) is quite linear and approximately ohmic.

I did calculations based on his readings and got these results.

Does this mean water is mostly ohmic whenever a current goes through it and if the probes were close together would it be the same level of ohmicness? How much does the electrochemistry reduce the resistance?

[studiot]

+1 for having a go, but realising the safety implications of higher voltages.

 

A few points about you results.

You are calculating resistance, whereas it is more usual to use conductance with liquids. Yes this is just the reciprocal of resistance but standard tables of values are all in conductances or conductivities.

Do you understand the correspondence between resistance and resistivity   v  conductance and conductivity ?

Also you have not put units to you 'resistances' I have multiplied my conductances in this graph by 10,000.

 

By the way Desmos.com/calculator is a useful free simple online graphing tool.

Looking at my graph which has only plotted the points, you are not justified in drawing the two straight lines as you have wiht only 4 points.

The graph 'turns over' to become asymptotic to somewhere around 4.5 conductance units.

 

Two other notes about your setup.

Yes there is an ohmic aspect to conductivity of water.
As the voltage and therefore the current rises some ohmic heating will inevitably occur raising the water temperature.
This is the basis for certain types of water heater.

The conductivity or resistivity of water, both pure and contianing impurities (eg tap water) is quite heavily temperature dependent.

[Sensei]

44 minutes ago, studiot said:

By the way Desmos.com/calculator is a useful free simple online graphing tool.

Thanks for sharing. Very useful. +1