Drift velocity and charging a capacitor.

[jhammin]

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?

 

[drummin]

Yes, the drift velocity is quite slow but there are a lot of electrons in the "electron gas" of the metal conductor.

 

[jhammin]

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.

 

[jhammin]

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.

 

[sardar]

The charging time of a capacitor is determined by various factors, including the capacitance of the circuit, the voltage applied, and the resistance in the circuit. It is not directly related to the drift velocity of electrons.

The drift velocity of electrons refers to the average speed at which electrons move through a conductor in response to an electric field. In a capacitive circuit, the electrons do not actually move from the conductors onto the metal plates of the capacitor. Instead, they accumulate on the plates, creating an electric field that stores energy.

The charging time of a capacitor can be calculated using the formula τ = RC, where τ is the time constant, R is the resistance in the circuit, and C is the capacitance. This formula can be derived using the principles of circuit analysis and does not involve the drift velocity of electrons.

In summary, while the drift velocity of electrons plays a role in the behavior of a capacitive circuit, it is not directly related to the charging time of a capacitor. The charging time is determined by other factors and can be calculated using the appropriate formula.