Drift velocity and charging a capacitor.

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Discussion Overview

The discussion revolves around the charging time of a capacitor and its relationship to drift velocity of electrons in a conductive material. Participants explore the concepts of charge movement, energy absorption in capacitive circuits, and the behavior of electrons in conductors.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions whether the charging time of a capacitor can be derived from the drift velocity of electrons and if charges move from conductors to the capacitor plates.
  • Another participant notes that while drift velocity is slow, the high density of electrons in the conductor contributes to charge movement.
  • A different participant suggests that the charging time is related to the energy absorption of the capacitor, indicating a possible self-resolution of their initial confusion regarding electron movement in wires.
  • Some participants express uncertainty about the concept of electrons entering or leaving a wire, with one acknowledging a misunderstanding related to the dispersion region in diodes and the availability of excess charges.

Areas of Agreement / Disagreement

The discussion contains multiple viewpoints regarding the relationship between drift velocity and charging time, and participants express varying degrees of understanding about electron movement in conductors. No consensus is reached on these points.

Contextual Notes

Participants mention assumptions about electron behavior and the influence of Coulomb forces, but these aspects remain unresolved within the discussion.

Who May Find This Useful

Individuals interested in electrical engineering, physics, or those studying capacitive circuits may find this discussion relevant.

jhammin
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I'm having trouble understanding where the charging time in a capacitor actually comes from. Is it possible to derive the \tau of a capacitive circuit from the drift velocity of the electrons? Are charges literally moving from the conductors onto the metal plates of the capacitor?
 
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Yes, the drift velocity is quite slow but there are a lot of electrons in the "electron gas" of the metal conductor.
 
The charging time of capacitor depends on its energy absorption, which can be used directly to get the drift velocity. Looks like I answered my own question.

I was caught up in the notion that electrons never actually enter or leave a wire. I'm not sure how i reached that idea because obviously the dispersion region in a diode depends on how many excess charges are available to be shared across the junction.
 
drummin said:
Yes, the drift velocity is quite slow but there are a lot of electrons in the "electron gas" of the metal conductor.

Ya, I was thrown off by the shear number of electrons. I was also thinking too much about the individual Coulomb forces between each electron.
 

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