I am looking into replacing my hob with an quick, induction type electric hob, but they stipulate that the the cookware must be ferrous. I have decent cookware, but how do I know if it is correct?
If a magnet sticks to it, it's ferrous.
I'd like to give a more elaborate answer, but there isn't anything more to it.
I have a pressure cooker made (or clad) in stainless steel. Please note that many types of stainless steel are only weakly magnetic. For stainless to be completely non-magnetic, however, it needs to be in an annealed state. Not likely with cookware.
Thus, I can tell between something that's weakly magnetic if you use a neodymium magnet. These are significantly stronger than your typical fridge magnet. Frequently they are sold online with the caution to not allow skin to get between two of these magnets as they can snap together forcefully and deliver a painful blood blister.
BTW, ferrous = made of, or contains iron, (all types of steel are ferrous).