Those cheap Chinese water heaters which are simply two plates of metal, one on live and one on neutral, how can they work? Because the resistivity of tap water apparently varies from 2 to 200 ohm metres. That's a range of 100 fold in possible power output. I assume the resistivity changes due to impurities like lime in hard water areas?
It does not seem practical. what are the plates, I suppose AC would limit electrochemical effects, but it does not sound practical.
As far as the resistance goes, I suppose with a mineral concentration the resistance would fall with temperature, but at 100C the bubbles would provide negative feedback.
Proof could be obtained by measuring the temperature. I would guess it never goes over 100C :-)
AB
They do seem to work - check out bigclive's videos on youtube.
I've not measured different waters as I only have access to Scottish tapwater and de-ionised water. It would be interesting for people around the world to measure the resistivity of their own tapwater.
Yes bubbling does make the current fall.
They used to make jug elements like that
They work best with Chinese water which is full of crap:-)
Mike
When I was a kid, we had a vaporizer that used 2 carbon rods, which were in a Bakelite tube, with the whole thing submerged in a large water bowl. It worked, but, even though we had city water (Chicago area), the carbon rods would get coated with minerals and would have to be cleaned from time to time. Otherwise, the output would be very low.
Big Clive did a review of these a couple of years ago
incorrect statements.
I can't believe I sat through that and nothing went bang.
Yes, explosions are much more fun.
But since the designer has no idea of the mineral composition of the water you're going to use, the output power could vary by a factor of 100. So you might buy one that's capable of 2kW and find you get a measly and utterly useless 20W.
And then the health and softy folk ruined it all.
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