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J.R. Buchanan


Transient response of a simple RC circuit

RC circuit here

The switch is closed at time=0. After the switch is closed, the voltage on the capacitor changes from its initial value to a value that aproaches Vb in an exponential manner.

The following equations describe the voltage change with regard to time.

Vc(t) = Vb + (Vc(0) - Vb)e^(-t/T)
T = RC


C     Is the value of the capacitor in farads.
e     is 2.718 (you knew that, right? :-) )(The base of the natural logrithm)
R     Is the value of the resistor in ohms.
t     Is the time in seconds after the switch is closed.
T     Is actually Tau, but that's not in ASCII (Which was all we could count
      on when this was posted)
      It is the time constant, the product of R and C
Vb    Is the voltage supplied by the voltage source.
      In this case, the battery symbol represents an ideal
      voltage source.
Vc(t) Is the voltage across the capacitor at the specified time.