Dunno, but I would guess yes, just the base, whatever ferromagnetic is.
I think my old pans (don't have one of those hobs anymore they did my head in!) only had the weird base, not the whole pan was detected. Because if I didn't have the pan just right, it'd pretend to boil my spuds and make me think my tea was nearly ready, but in fact the little blighters were stone cold and rock hard.
So I'm thinking just the pan, or at least on mine. I bet somebody has made better ones now. But it's put me off for life.
Can't beat fire when it comes to man-cooking eh?!
So I'm thinking just the pan, or at least on mine. I bet somebody has made better ones now. But it's put me off for life.
Can't beat fire when it comes to man-cooking eh?!
Just the base needs to be... but the best pans to used are cast iron ones... they work really well ! I have a few aluminium pans that have had like a ferro-magnetic matrix inserted into the base... they work well too...
Look for this marking: 
You can test the base of a pan with a magnet to see if it is ferromagnetic. Do not use pure copper, aluminium or tin pans. Using the wrong pan may damage the hob position.
There is actually quite a lot of interesting physics to 'optimise' for a pan to be good for an IH hob; frequency, skin depth, size, base thickness, permeability, hysteresis, eddy currents and their flux patterns, Joule heating, skin resistance........
If you are interested read this link or if busy just the 'cookware' section:
Induction cooking - Wikipedia - https://en.wikipedia.org/wiki/Induction_cooking
You can test the base of a pan with a magnet to see if it is ferromagnetic. Do not use pure copper, aluminium or tin pans. Using the wrong pan may damage the hob position.
There is actually quite a lot of interesting physics to 'optimise' for a pan to be good for an IH hob; frequency, skin depth, size, base thickness, permeability, hysteresis, eddy currents and their flux patterns, Joule heating, skin resistance........
If you are interested read this link or if busy just the 'cookware' section:
Induction cooking - Wikipedia - https://en.wikipedia.org/wiki/Induction_cooking
rupertcacatua
DIY
Super interesting. Basically paramagnetic metals (Al, Cu) offer less resistance to the induced current thus producing no/less heat whereas Fe based ferromagnetic materials are not great conductors and thus, offer great resistance, thereby heating up! Still, my question was specific about whether a fully magnetic vessel will heat up better than a base-only magnetic vessel. Can't find an answer to that...I guess fully magnetic will be better but not sure the IH plate "cares" about more than the base of the vessel...
Re#20 - fully magnetic pan or just magnetic base pan......
The majority of the magnetic interaction between the hob excitation coil and the pan is taking place in a thin surface layer at the bottom the pan's base. An alternating magnetic field does not penetrate far into a conductor and decreases in depth with increasing frequency of alternation.
The strength of the mutual coupling between the areas/regions on the pan and the hob coils reduces as they become farther apart so again the majority of coupling is to the base since it is flat and adjacent to the coils.
One can also visual that the base will 'shield' to some extent the upright sides of the pan thus reducing further mutual coupling.
Another consideration is that the regions in the sides into which are induced electromotive fields are shorter in dimensions or put crudely small circumference 'circles/bubbles of metal' ; the net electromotive force (emf) around such regions/paths is consequently of low value than in the longer paths/bigger regions of the flat base. Most of the magnetic/electric reaction then to the action of the exciting magnetic field is taking place in the base not the sides.
The large eddy current fluxes caused by the induced emf loops are in the base. And they flow in a thin skin region on the bottom surface. So because it is a thin conducting region the resistance to the electron flows/eddy currents is effectively higher than that of the bulk of the base; beyond the skin depth is in effect 'not used' for eddy current fluxes.
The base is then where the bulk of the interaction takes place between the alternating mag field and currents to flow in the skin layer. In the skin layer these current flows through the skin resistance produces Joule/Ohmic heating of the skin layer (IsquaredR). Thermal conduction of this heat through the pan and thence into its contents results in cooking.
I think the IH makers are working on even higher frequency excitation coils which would allow 'ordinary' copper, aluminium, non ferro stainless steel pans to be used.
The skin depth is approx given by :
What this tells us that the skin is thicker for materials with low permeability like copper and decreases in thickness with frequency. A thicker skin means lower R in IsquaredR so less Joule/Ohmic unless one can increase the size of the eddy currents by more powerful excitation fields.
Copper, Aluminium, non ferro stainless steel happen to be very good conductors and have very low permeability. To employ them usefully for IH cooking pans needs a higher frequency excitation field.
Skin depth in copper
Producing high power excitation fields at higher frequencies requires more expensive power electronics than using a lower frequency (20-40kHz) and demanding 'special' pans to be employed.
Briefly, ferromagnetism adds to a pan's goodness for IH because of hysteresis losses manifest as heat.
Or something like this - it gives you the gist of what is going on.
The majority of the magnetic interaction between the hob excitation coil and the pan is taking place in a thin surface layer at the bottom the pan's base. An alternating magnetic field does not penetrate far into a conductor and decreases in depth with increasing frequency of alternation.
The strength of the mutual coupling between the areas/regions on the pan and the hob coils reduces as they become farther apart so again the majority of coupling is to the base since it is flat and adjacent to the coils.
One can also visual that the base will 'shield' to some extent the upright sides of the pan thus reducing further mutual coupling.
Another consideration is that the regions in the sides into which are induced electromotive fields are shorter in dimensions or put crudely small circumference 'circles/bubbles of metal' ; the net electromotive force (emf) around such regions/paths is consequently of low value than in the longer paths/bigger regions of the flat base. Most of the magnetic/electric reaction then to the action of the exciting magnetic field is taking place in the base not the sides.
The large eddy current fluxes caused by the induced emf loops are in the base. And they flow in a thin skin region on the bottom surface. So because it is a thin conducting region the resistance to the electron flows/eddy currents is effectively higher than that of the bulk of the base; beyond the skin depth is in effect 'not used' for eddy current fluxes.
The base is then where the bulk of the interaction takes place between the alternating mag field and currents to flow in the skin layer. In the skin layer these current flows through the skin resistance produces Joule/Ohmic heating of the skin layer (IsquaredR). Thermal conduction of this heat through the pan and thence into its contents results in cooking.
I think the IH makers are working on even higher frequency excitation coils which would allow 'ordinary' copper, aluminium, non ferro stainless steel pans to be used.
The skin depth is approx given by :
What this tells us that the skin is thicker for materials with low permeability like copper and decreases in thickness with frequency. A thicker skin means lower R in IsquaredR so less Joule/Ohmic unless one can increase the size of the eddy currents by more powerful excitation fields.
Copper, Aluminium, non ferro stainless steel happen to be very good conductors and have very low permeability. To employ them usefully for IH cooking pans needs a higher frequency excitation field.
Skin depth in copper
| Frequency | Skin depth (μm) |
|---|---|
| 50 Hz | 9220 |
| 60 Hz | 8420 |
| 10 kHz | 652 |
| 100 kHz | 206 |
| 1 MHz | 65.2 |
| 10 MHz | 20.6 |
| 100 MHz | 6.52 |
| 1 GHz | 2.06 |
Briefly, ferromagnetism adds to a pan's goodness for IH because of hysteresis losses manifest as heat.
Or something like this - it gives you the gist of what is going on.
Last edited:
rupertcacatua
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