ELEC 242 Lab
Background
The solution to a first order circuit with constant
excitation is completely
determined by three parameters:
the time constant, the initial value, and the final value.
The form of this solution is shown
graphically in
the following figure.
With constant sources
we can generally find the initial and final values
by inspection or by solving simple resistive circuits.
We may express the general solution in terms of these values
We can also use Thevenin's theorem to find the equivalent
resistance, 
as seen by the capacitor or inductor, and
thereby determine the time constant as 
or 
.