Question regarding conduction current

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    Conduction Current
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Discussion Overview

The discussion revolves around the behavior of conduction current in a capacitor filled with a dielectric material that has non-zero conductivity, particularly in the context of a DC voltage source. Participants explore the implications of displacement current and conduction current under different conditions, including the presence of leakage current.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that under a DC voltage source, the displacement current and conduction current of the wire are both zero, while the conduction current density in the dielectric remains non-zero due to its conductivity.
  • Others propose that the DC leakage current is continuous through both the wire and the dielectric, suggesting that any leakage current in the capacitor must be supplied by the wire.
  • A participant questions whether the equation I=CdV/dt accounts for DC leakage, proposing that the actual conduction current in the wire may be the sum of the displacement current and the conduction current density integrated over the dielectric.
  • Another participant introduces the idea that a practical capacitor can be modeled as an ideal capacitor with additional resistances, indicating a more complex behavior than initially considered.

Areas of Agreement / Disagreement

Participants express differing views on the treatment of leakage current and its implications for the equations governing conduction and displacement currents. The discussion remains unresolved, with multiple competing perspectives on the nature of the currents involved.

Contextual Notes

Participants highlight potential limitations in the equations used, particularly regarding the treatment of leakage current and the assumptions made about the behavior of the capacitor under DC conditions.

yykcw
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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?
 
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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.
 

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