[Physics] What will happen if we place salt water on a induction cooker

everyday-lifeinduction

As we know that induction cooker works on the principal of induction of current in a conducting plate. So I just wanted to know what will happen if we place salt water in a plastic container on the induction cooker will it get hot as it is also a conductor or nothing will happen?

Best Answer

Being a conductor is not enough, you also have to have some magnetic properties in order to induce current in some material. That's why not all pan "work" on an induction cooker.

Addendum

Bobby Bennett's answer show me that I have been a bit too concise in my previous answer. Here is a more complete one:

  • As stated by Bobby Bennet, magnetic field can induce current in any material even slightly conductive due to the electromotive force given by the Lenz-Faraday law: $e=-\frac{d\Phi}{dt}$ where $\Phi$ is the magnetic flux through the system.
  • The transmitted power will be proportional to $e^2/\rho$ (due to Joule's law) where $\rho$ is the resistivity of the medium so that it's easier to heat good conductors which have low resistivity.
  • the electromotive force $e$ is higher when
    1. the magnetic field is varying rapidly: its frequency of variation has to be high (20 to 50kHz usually)
    2. the magnetic field in the medium is strong, which is where ferromagnetism enters in consideration. The magnetic field "felt" inside a medium is proportional to the exterior magnetic field with a factor given by the relative magnetic permeability of the medium $\mu_r=1+\chi$ where $\chi$ is the magnetic susceptibility. Susceptibily of iron is about $200$ when the one from aluminum is around $2.10^{-5}$, which explains why you have to have a much more special set up in this video: the current used to produce the magnetic field have to be 200 higher than the one that would have been needed to transmit the same power to iron.

In conclusion, you can for sure induce current in your salted water and increased it when increasing it's conductivity with ions but without the "doping" due to ferromagnetic properties, you would not be able to heat it with a usual "kitchen" induction system.