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Drift velocity and charging a capacitor.

  1. Jun 25, 2012 #1
    I'm having trouble understanding where the charging time in a capacitor actually comes from. Is it possible to derive the [itex]\tau[/itex] 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?
  2. jcsd
  3. Jun 25, 2012 #2
    Yes, the drift velocity is quite slow but there are a lot of electrons in the "electron gas" of the metal conductor.
  4. Jun 25, 2012 #3
    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.
  5. Jun 25, 2012 #4
    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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