Question regarding conduction current

AI Thread Summary
The discussion centers on the behavior of conduction and displacement currents in a capacitor filled with a conductive dielectric when connected to a DC voltage source. It highlights that while the displacement current and conduction current in the wire are zero in a DC scenario, the conduction current density in the dielectric remains non-zero due to its conductivity. The conversation also touches on the concept of DC leakage current, which continuously flows through both the wire and dielectric, necessitating a supply from the wire. Additionally, it suggests that the equation I=CdV/dt does not account for this leakage, proposing that the actual conduction current should include both leakage and displacement components. The practical modeling of a capacitor incorporates resistances to reflect these behaviors accurately.
yykcw
Messages
12
Reaction score
0
Assume a voltage source connected to a capacitor which filled with a dielectric material having non zero conductivity, then,
displacement current=conduction current of the wire=CdV/dt
while conduction current density of the dielectric=σE=σV/d
But considering dc source,
displacement current=conduction current of the wire=0,
while conduction current density of the dielectric=σV/d and not equals to zero
Why there will be a contradiction?
 
Last edited:
Physics news on Phys.org
yykcw said:
Assume a voltage source connected to a capacitor which filled with a dielectric material having non zero conductivity, then,
displacement current=conduction current of the wire=CdV/dt
while conduction current density of the dielectric=σE=σV/d
But considering dc source,
displacement current=conduction current of the wire=0,
while conduction current density of the dielectric=σV/d and not equals to zero
Why there will be a contradiction?

Welcome to the PF.

The DC leakage current is continuous through the wire and the dielectric. If there is leakage current in the capacitor, it has to be supplied by the wire.
 
berkeman said:
Welcome to the PF.

The DC leakage current is continuous through the wire and the dielectric. If there is leakage current in the capacitor, it has to be supplied by the wire.

So the equation I=CdV/dt has not considered the dc leakage? the actual conduction current in the wire is=∫σEdS?
How about at other frequency? Is the actual conduction current inside the wire equals to CdV/dt+∫σEdS(σ is the conductivity of the dielectric) but not just CdV/dt?
 
A practical capacitor can be modeled as an ideal capacitor with two resistances, one in series and the other in parallel.
 
I was using the Smith chart to determine the input impedance of a transmission line that has a reflection from the load. One can do this if one knows the characteristic impedance Zo, the degree of mismatch of the load ZL and the length of the transmission line in wavelengths. However, my question is: Consider the input impedance of a wave which appears back at the source after reflection from the load and has traveled for some fraction of a wavelength. The impedance of this wave as it...
Back
Top