I have two samples in the same nature (same material) with different thickness, the one is 1mm and the other is 4mm. I applied on theses two levels of voltage: 100V and 400V so the field is the same (100V/mm).
Although the permittivities of both are the same, the loss in case of 400V is higher than the last in all range of frequency, the look of loss index is similar and is like conduction cause (straight line increase in lower frequency). I tried to find a theory in order to explain that but always in fail. The theory of Lampert on the influence of space charge in conduction current seems not work because i found the relation
I ~ V^2/L^3.
Can you suggest me an another theory on this, knowing that both sample contains an amount similar of water.
Thanks a lot
The newbie of dielectric