I Why induction requires a magnetic material to produce a current

[Wille]

TL;DR Summary

I wish to understand (on quantum/atom level) how the magnetic properties of atoms/molecules are creating electron movement (current) when placed in a magnetic field. For instance, a copper (a non magnetic metal) pot will not work on an induction stove even tough it is a very good electrical conductor.

I can create a fairly strong magnetic field by leading current through a copper coil. However, I cannot then with that magnetic field create a current (not a useful one at least) in an object made out of copper. I understand that this is because copper lacks of magnetic properties. For instance, a copper pot will not work on an induction stove even tough copper is a very good electrical conductor. The magnetic field however is created from an alternating current moving through a copper coil.

How do the magnetic properties of the atoms/molecules create a current when placed in an magnetic field? What makes electrons, in this case, start to move from atom to atom (i.e. a current)? Why will a non magnetic material placed in an magnetic will not produce a current?

Thanks.

 

[trurle]

a copper (a non magnetic metal) pot will not work on an induction stove even tough it is a very good electrical conductor.

You misundestood. Copper is fine for induction oven.

How do the magnetic properties of the atoms/molecules create a current when placed in an magnetic field?

Magnetic field do not create a current. Rather, magnetic field redirects current. To produce current, you need changing magnetic field. See "Lenz Law".

What makes electrons, in this case, start to move from atom to atom (i.e. a current)? Why will a non magnetic material placed in an magnetic will not produce a current?

Very low activation barrier against electron movement (free Fermi surface) make electrons mobile under electric or changing magnetic field. See "Electronic band structure".

 

[Dr_Nate]

Exactly because copper is good conductor is the reason it is not the best for an induction stove. You need resistance to create heat.

Electrons do not jump from atom to atom.

 

[scottdave]

This question has intrigued me to read more about it. From what I've come across, so far, it is not the current and resistance which causes most of the heat in the pan, but the little magnetic dipoles in the iron moving back and forth, causing heat due to friction.

 

[Dr_Nate]

@Wille and @scottdave appear to be correct! Magnetic materials are easier to heat by induction because of the hysteresis effect and their higher magnetic permeability. You must do work to overcome the residual magnetization.

https://dw-inductionheater.com/induction-heating-principle.html

 

[Wille]

This question has intrigued me to read more about it. From what I've come across, so far, it is not the current and resistance which causes most of the heat in the pan, but the little magnetic dipoles in the iron moving back and forth, causing heat due to friction.

@scottdave Thanks! Great answer! That make sense and explains why the metal has to be magnetic and why it is not enough with a metal being a good electrical conductor. It is foremost not a matter of moving electrons.

Many sites say that it is a matter of current and resistance though, for instance Wikipedia:
https://en.wikipedia.org/wiki/Induction_cooking
Here it is explained that the poor magnetic properties of copper makes it harder to get a concentrated current which in term makes it harder to produce heat...

 

[Wille]

Electrons do not jump from atom to atom.

@Dr_Nate Ok I thought that that is how electrons move. I.e. a current is free electrons moving from atom to atom. As the electrons collide with atoms, the kinetic energy of those atoms increases, i.e. heat is created.

 

[Dr_Nate]

@Dr_Nate Ok I thought that that is how electrons move. I.e. a current is free electrons moving from atom to atom. As the electrons collide with atoms, the kinetic energy of those atoms increases, i.e. heat is created.

Some models picture electrons in metals as tiny little tennis balls. Quantum mechanical solutions have the wave function of electron as plane waves spread out through the whole metal. Imperfections and other things do cause the electron to scatter and create heat.