Induction cooktops (1 Viewer)

[undalay]

why must the pot be a ferromagnetic materials such as Iron, but cannot be a material such as copper or aluminum.

Eddy currents are produced in all conductors right?
So why do only Iron (or Iron alloy) pans work?

I get why glass pans don't work, thats because glass isn't a conductor.

 

[shanks27]

they don't have to be magnetic to work. The reason iron is often used as when alum. or coppper is used they will fly off. We foudn this in a first hand expierment. But copper and Alum. are better for cook tops as they have lower resistance and thus higher current so better heating. So the most common cookware used is a pan with an alum. or copper core, which heats up qucikly using eddy currents which is then surrounded by either stainless stell or iron which still heat up but also will stick or not fly off the stove top.

hope this helps

 

[undalay]

I don't undestand, why does one material coz the pot to fly off, but not the other?

and i'm pretty sure the the higher the resistance the higher the heating.

 

[minijumbuk]

I think it's because Copper has a very low resistance. Iron has a high resistance, so the higher resistance, the more current will be lost as heat energy. The more loss in current as heat makes Iron a suitable material for converting that electrical energy from the eddy currents into heat energy for cooking.

 

[undalay]

i just checked the dotpoint book and it says aluminium or copper-based saucepans will not work well as they have too low a resistance to generate the heat required.

However does ferromagnetic material affect eddy currents in anyway?
and how?

(maybe it magnifies the effect, but how)

 

[minijumbuk]

I think that ferromagnetic/non-ferromagnetic material does NOT affect the eddy currents, ie. changing it to higher/lower.

What I think is the logic is here that since ferromagnetic material has more resistance, then the eddy currents generated at the base will be lost as heat energy more than eddy currents lost as heat in the non-ferromagnetic material.

 

[shanks27]

we were speaking about this with our teacher the other day. And even the internet often says- higher resistance= more heating, that isn't right. As an AC current = change in flux= eddy currents made using P= I^2R,the less resistance= higher current, more power or high heating. The higher the current, the more heating.

The reason that Aluminum flies off a solinoid or electro magnet is to due with diagnetism repulsion -http://en.wikipedia.org/wiki/Diamagnetism and "
"Take a flat aluminum ring, put it over a strong
electromagnet and switch on the current. The disk will fly off the
solenoid with quite a speed. Starting with this principle of
DIAMAGNETIC REPULSION" from (http://keelynet.com/gravity/grav2.txt"

Try the expierment at school, get a solinoid and place an iron ring and aluminum ring onto it you will find that the Aluminium ring will fly off

hopefully this will help my explanation more clear. Dw my entire class did the normal- iron works best answer and our teacher gave us all
1 and 2s out of 8 and then explained why aluminium is the best metal to be used and why it flys off.

hope this helps again

 

[samwell]

I think the main reason ferromagnetic iron is used is because its the most efficient to use in terms of power and heat loss. Ferromagnetic materials usually intensify the magnetic field and this would increase the heat produced by an induction cooktop bcoz of the eddy currents produced. [not sure wat i just said but hope it helpz]

 

[minijumbuk]

we were speaking about this with our teacher the other day. And even the internet often says- higher resistance= more heating, that isn't right. As an AC current = change in flux= eddy currents made using P= I^2R,the less resistance= higher current, more power or high heating. The higher the current, the more heating.

The reason that Aluminum flies off a solinoid or electro magnet is to due with diagnetism repulsion -http://en.wikipedia.org/wiki/Diamagnetism and "
"Take a flat aluminum ring, put it over a strong
electromagnet and switch on the current. The disk will fly off the
solenoid with quite a speed. Starting with this principle of
DIAMAGNETIC REPULSION" from (http://keelynet.com/gravity/grav2.txt"

Try the expierment at school, get a solinoid and place an iron ring and aluminum ring onto it you will find that the Aluminium ring will fly off

hopefully this will help my explanation more clear. Dw my entire class did the normal- iron works best answer and our teacher gave us all
1 and 2s out of 8 and then explained why aluminium is the best metal to be used and why it flys off.

hope this helps again

Isn't the reason why current contributes to heat because of the RESISTANCE? Current itself doesn't just "break up" into heat energy...
So if you say P=I^2 R, and then say that LOWER resistance leads to HIGHER power... That's a pretty strange way to put it.
Seeing as I CAN BE set as constant (put it on 10 amps on the cooktop or something), then P will depend if R is high or low. If R is high, then change in energy is greater, and R is lower, then change in energy is less?