Bruce Farquhar wrote:
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?

They used to make jug elements like that