Permittivity values in conductors

[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

 

[Hassan2]

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

High ksnf3000,

electric current density :

$J=σE$

displacement current density :

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

for a steady stead sinusoidal field,

$J_{d}=jωD=jωεE$

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.

 

[ksnf3000]

Thanks for your reply Hassan2.

The negative sign indicates the loss the imaginary part suffers, right??

 

[Hassan2]

Thanks for your reply Hassan2.

The negative sign indicates the loss the imaginary part suffers, right??

that j is not supposed to be there. The parameters are real, so, the right hand side must be real too. When comparing their magnitudes, j and also -1 becomes 1.