RC Circuits

Given the formula for time constant delay defined in RC Formulation, we can model the voltage in a RC circuit as an exponential curve:

5 tau rule

As a rule, we consider $V(t)$ to be zero after 5$\tau$, even if this is not mathematically true. This is also true for charging instead of discharging – something is fully charged after $5\tau$.

The whole point of this is that the curve behaves the same for any $\tau$, but you can pick and choose the $\tau$ value by choosing values for $R$ and $C$.