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Electric Flux Density Theory

Electric Flux Density Theory

Electric Flux Density Theory

It is my understand that the electric flux decreases as the permittivity of a medium increases.  This makes since, because permittivity is the resistance of a medium to an electric field.  However, this seems to contradict the formula

D = (permittivity)E

where D is the electric flux and E is the electric field intensity.  Base on this formula it seems that the electric flux increases as permittivity increases.

What am I missing?

RE: Electric Flux Density Theory

You have to define what is changing and what is constant, in other words what is the circuit you are thinking about.

If you fix the applied voltage and distance between electrodes, then (under parallel plate type / uniform field assumptions), E  = V / distance is constant.   Increasing  Epsilon would increase D for this given fixed E.

If you fix the free charge, then D is constant.  Increasing Epsilon would decrease E.  The physical situation would be two floating electrodes with charge... insert different dielectrics between those electrodes and measure voltage.

(2B)+(2B)'  ?

RE: Electric Flux Density Theory

Thanks for the response.  I realized that my initial misunderstanding was due to mixing resistance with impedance.  A medium with a higher permittivity value ε (farads per meter) will have a lower impedance value, because Z = 1/jωC.

Mathematically this makes sense, because as impedance Z decreases permittivity ε increases as does electric flux D given a fixed electric field intensity E according to D = εE .

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