The electromotive force is
, where
is capacitance in farads,
is resistance in ohms,
is charge in coulombs.
Substitute
in
.

Substitute
and
.






Apply integral on each side.
\


.
The initial condition is
when
.
Substitute
and
in
.

.
Substitute
in
.
.
The limiting value of charge is
.



.
The limiting value of the charge is
.
.
The limiting value of the charge is
.