How did the scientist measure the dielectric constant? Does the dielectric constant relate to an alignment with the electric field?

Question

I heard that the dielectric constant of water is around 78. When we think about the way we get the $\kappa$ of water,

Can we get the $\kappa_{water}$ by putting the water molecules on the $\vec{E}_{free}$ and comparing with the $\vec{E}_\text{net}$? If not, how did the scientist measure the magnitude?

From the equation $$ \vec{E}_\text{net} = \frac{\vec{E}_\text{free}}{\kappa}, $$ I thought a material itself can easily make induced charges if its $\kappa$ is relatively large. However, I was curious about the relationship between the magnitude of $\kappa$ and the tendency of aligning on the electric field. The $\kappa$ between a water molecule and ethanol, $$ \kappa_{ethanol} < \kappa_{water} $$

Then, can we say water molecules are easier to align with $\vec{E}_\text{free}$ compare to ethanol because the water can make more induced charges?

Thanks.

Answer 1

dc or low frequency permittivity measurements are usually capacitance measurements in a bridge, see. At a higher frequency, microwaves and beyond, it is usually done in some form of cavity for its resonance shift or in a closed or open waveguide through direct reflectivity, if money is no problem, although the instrumentation method is getting cheaper and cheaper, and using this kind of equipment.