Electrochemistry: Liquid Power Resistor for 2000VAC

Why not experiment with it since you already have the setup? Try putting a

100k res in series and measure the voltage. Sweep up to 200VAC and see if the volage devates from 100VAC at the divider.

I imagine if the liquid gets hot the resistance will change so you might try an ice bath. You could then try with and without the ice bath and find the deviation to get some temperature dependence relation.

Trying out another "natural selection" experiment ?:-) ...Jim Thompson

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Copper will be electrolyzed into solution and the resistance will drop. And bubbles will form on the electrodes and resistance will increase!

Neither happens fast at low currents.

But the dissipation is only 40 watts for 5 seconds. A string of, say, ten or so 2-watt carbon film resistors would work fine.

John

lol :)

No, but the resistance at the electrode/liquid interface may vary even over a few seconds.

Put it in series with a known resistor and put a scope HV probe on it. Check the divider ratio with various voltages over the 5 second time.

--
Virg Wall

Yup. I don't have any but odds are better that the surplus store will have 2W power resistors as opposed to a single power resistor. It'll probably be better if I run out and get the resistor/s. groan :( ..

Not at AC faster than the diffusion rate of the liquid. Even a pokey 60Hz modulation is notorious for having terrible electrolysis capacity.

Tim

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I might. I do have a isolated variable transformer and a single 2W 100k resistor. And I could try graphite electrodes. I found a pencil.

I'm just wobbling between curiosity /laziness vs practicality. To set up an experiment or... forget about that and run off to the surplus store and get some real resistors. mmm

If it's just for an experiment then why not put the resistor in an ice bath? I'm not sure how well this will help out but it should easily allow a 1/4W resistor to last 5 seconds? I imagine the resistor may last 5 seconds without the bath. The main issue is, of course, that the resistance may change drastically but you could try it and see.

Use the 2W 100k resistor in an ice bath and you should be fine. You could put 200 liquid containers in series or parallel if you really wanted to have fun ;)

I'll do that. Will report later if the 2W 100K with 2000VAC across it failed in cold bath.

If you can, monitor the current or use a voltage divider to record the voltage and see how long it takes to change... or record the temperature of the bath.

I've seen big (as in 50' high, 12 megavolt) Marx generators that used water-filled clear plastic pipes, about like a garden hose, as the capacitor charging resistors. They were blue inside, copper sulphate solution I think.

John

That must be Lenin generator.

VLV

I came up with a neat isolated DC-DC converter circuit. I showed it to Phil Hobbs and he called it the Groucho Marx Generator.

John

You might want to insulate the wiring too, just to be on the safe side.

Yes. Everything associated with Marx is infallible by definition. However, if you mentioned Marx, you absolutely must mention Lenin unless you are speaking in pure historical context :-)

VLV

try

I do have CuSO4.

'The following cations have lower electrode potential than H+ and are therefore suitable for use as electrolyte cations: Li+, Rb+, K+, Cs+, Ba2+, Sr2+, Ca2+, Na+, and Mg2+. Sodium and lithium are frequently used, as they form inexpensive, soluble salts.'

Those are all group 1 and 2 elements.. So I suppose I should use CuSO4 to prevent H2 and O2 bubbles creating resistance error on the electrodes.

btw.. I barely know electrochemistry.

EBG do a nice range. You could for example put 5 560k SSP52 in parallel:

Mark.

I might track down where I can get one.