As we know,
for simple systems C ＝(εA) / l where C ＝ capacitance, ε ＝permeability A ＝cross-sectional area and l ＝thickness of membrane
for complex systems C ＝((εA) / l) - j(1 / R*ω) and ε ＝((C*l) / A) - j(1 / ρ*ω)
My question is, in a porous membrane, increasing amount of water contents cause an increase in relative permitivity which results decrease in capacitance.
Physically, it is logical but the above relation does not provei t.
my problem with this view is that in biological membrane Capacitance IS NOT A CONSTANT because the membrane field electrical potential and shape or structure chenge with potential.
Hi, Ali,
As the porous membrane absorbs water, not only the "new material" permittivity is increased, but also the membrane thickness may also be increased. As you observed a higher capacitance, that means the thickness has presented an increase higher than the observed for your "water+membrane" permittivity. The higher the thickness, the lower the final capacitance will be.
One way to be sure about the analysis I have made is to measure the thickness of the membrane before and after water absorption.
I hope this can help you,
Miguel
Dear Ali,
You wrote:
My question is, in a porous membrane, increasing amount of water contents cause an increase in relative permitivity which results decrease in capacitance.
The increase in the water content for sure increases the effective dielectric consatnt at lower frequency because water has much higher dielectric consatnt that the organic materials. So the capacitance increases not decreases!!
So, there is a conflict with your statement. You need to clarify your point of view.
Best wishes
Please read my book
The American University Laboratories For Electrical Engineering Part 2
I hope you find
a good example .
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