On 2014-11-28 06:51, drlegendre . wrote:
On Thu, Nov 27, 2014 at 2:11 PM, Chuck Guzis <cclist at sydex.com> wrote:
This goes counter to my experience. Any utensil that passes the "magnet
test" will work; any that don't, don't.
I've never found an exception to this.
In retrospect, my comments may have been a bit pedantic - as you have
found, the 'magnet test' is more than likely an effective method for
selecting compatible cookware.
The point of my post, was that it's not actually the presence or lack of
ferromagnetic characteristics which are responsible for the compatibility
or incompatibility of the given cookware. Let me see if I can explain this
without further muddying the waters:
I think we all understand that induction heating is the result of eddy
current propagation within the cookware - this is one of the reasons that
it's more efficient than traditional contact-coupled resistive elements
operated off AC mains power. But like any _resistive_ heating element, the
cookware must offer sufficient _resistance_ to the impressed currents to
produce any heating effects - that's just I^2*R.
In the case of most copper, antimagnetic stainless or aluminum vessels, the
eddy currents actually propagate a bit too well - that is, the effective
resistance of the imposed current path is too low for any useful ohmic
heating to take place. In other words, the currents flow, but the voltage
drops are inconsequential.
Or that's how I understand it. As ever, I await my ongoing education.. ;-)
That sounds a bit weird, as I would expect the current resistance in
iron should be pretty low as well. Or is it really way higher than in
copper or aluminium?
The magnetic properties seems to be the common factor in my experience
as well. Not sure how they relate to electric resistance...
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