Permittivity values in conductors

1. Mar 3, 2012

ksnf3000

Hello All,

I am a masters student in electronics engg and reading technical electrodynamics. Please let me know when the electric current density becomes more than the displacement current (for a conductor ) why is the value of ε≈-jσ/ω

Quick replies will be highly appreciated!!

Thanks and Regards,

ksnf3000

2. Mar 3, 2012

Hassan2

High ksnf3000,

electric current density :

$J=σE$

displacement current density :

$J_{d}=\frac{\partial D}{\partial t}$

$J_{d}=jωD=jωεE$

the ratio is $\frac{ωε}{σ}$

when $ωε=σ$, the magnitudes become the same. Considering typical values of the parameters, this happen at very high frequencies.

I hope that helps.

3. Mar 3, 2012