How does dielectric heating actually work?

[Experience111]

Hi everyone,

I'm currently working on a research project about dielectric heating of some materials and I'm trying to understand the physics of this phenomenon before going any further. I'm especially trying to understand the concept of complex dielectric constant and loss factor. I'm completely lost because I keep coming across two contradictory explanations:

1. The dielectric heating is due to the movement of rotating dipoles (aligning with the alternating electric field) which creates heat
2. "As the frequency increases further a point is reached where the reorientation polarization fails to follow the applied field and contributes less to the total polarization. The fall of the effective polarization manifests itself as a fall in the [real part of the] dielectric constant and a rise of the loss factor. Energy is now drawn from the system and dissipated as heat into the material"

So on one hand I'm told that it is the movement of the dipoles that causes heat, and on the other hand I'm told that it is the failure of the dipoles to follow the electric field that causes heat which doesn't make much sense to me.

Could somebody be kind enough to help me make sens of it all ? Thank you :)

 

[Charles Link]

It appears you are basically referring to how "microwave ovens" do their heating. I'm not entirely sure of this, but I believe there is often a resonant frequency of a particular contribution to the dielectric component just before that component drops out. According to Kittel's solid state physics, there are 3 contributions to the dielectric constant: dipolar, ionic, and electronic. On p.411 of his book, he shows a graph of the polarizability as a function of frequency: The dipolar contribution drops off and he shows no resonance in the dropoff, but with the ionic and electronic contributions, there is a sharp temporary increase in the polarizability with frequency, (most likely due to a resonance) before it drops off.