A lot of pots have a double-wall bottom. Inside this double wall is magnetic material. Mine is like that. The pot itself isn’t magnetic but the bottom is.
My kettle doesn't have the tri-ply bottom. It's just your common-variety, non-magnetic stainless. I didn't think about how I was going to heat the wort. I figgered on my gas stove would be good enough. Then it came out that gas stoves are going to kill us all within the next fifteen minutes. It's so windy and so dusty where I live that I fear an open-top boil outside will end with dust and dry leaves in my wort, so a propane burner is out. I guess I can use my stove. I'm thinking I'll boil two-thirds of my fermentable volume (4.67 gallons in the kettle for a total of seven gallons to ferment); that should be watery enough to prevent scorching during the sixty-minute boil. 7000 BTU ought to do that, don'cha think?
Will still keep looking for a hot plate having a single cast-iron burner in the 1800-watt category.