# Drawing graph with unknown constant [closed]

Q=VC(1-e^\frac{-t}{RC}) Is it possible to plot this function, Q-t graph? V and C are unknown constants.

• That should be a series of curves (Q-t graph). V does not matter here in terms of shape (so you may even normalize the value of Q by VC). Resistor and capacity values do matter so you may choose a series of parameters and draw them on the same figure. That will show how the charging works with respect to parameters R and C. (For example, the smaller R is, the faster the charging goes). Nov 7, 2022 at 5:15

Like this:

\documentclass[tikz,border=1cm]{standalone}
\begin{document}
\begin{tikzpicture}
\draw[very thin,color=gray!15,step=1] (0,0) grid (12,4);
\draw[-latex] (-0.2,0) -- (13,0) node[right] () {$t {(\sec)}$};
\draw[-latex] (0,-.3) -- (0,4) node[above] {$Q (\times 10^{-5}$ C)};
\foreach \i in {0,4,...,13}
\draw[gray!65] (\i,.1)--(\i,-.1) node[below] {$\i$};
\foreach \i in {0,1,...,4}
\draw[gray!65] (.1,\i)--(-.1,\i) node[left] {$\i$};
\draw[cyan,line width=3pt,domain=0:13] plot(\x,{3.75*(1-exp(-\x/3))}) ;
\draw[red,dashed,line width=.5pt] (13,3.75)--(0,3.75) node[left] () {3.75};
\end{tikzpicture}
\end{document}


Output:

The plot is done with this assumptions: R = 2.0 MΩ, C = 1.5 μF, V0 = 25 V.