At t = 0, the switch is at Position 1.

We note that $q(0)=0.$

MATH

MATH

MATH

Using SNB to solve this differential equation, we have:

MATH


NOTE: By differentiating, this gives us:

MATH

We need to find $\tau $:

MATH.

Now, at $t=0.00025$, the charge will be:

MATH


At $t=\tau $, switch at Position 2:

Applying the formula MATH again:

MATH

NOTE: The negative voltage is because the current will flow in the opposite direction through the resistor and capacitor.

Once again, we solve using Scientific Notebook:

MATH

Exact solution is:

MATH

So the current transient will be:

MATH

MATH

This expression assumes that time starts at $t=0$. However, we moved the switch to Position 2 at $t=0.00025$, so we need:

MATH

So the complete current transient is:

MATHfor MATH

MATHfor $t>0.00025$

The graph is very interesting:

6_RCex3__27.png