How To Draw Equipotential Line In Latex

The electric field lines and equipotential surfaces of a indicate charge.
Edit and compile if you like:
% Author: Izaak Neutelings (July 2018) % page 8 https://archive.org/details/StaticAndDynamicElectricity % https://tex.stackexchange.com/questions/56353/excerpt-x-y-coordinate-of-an-capricious-point-on-curve-in-tikz % https://tex.stackexchange.com/questions/412899/tikz-calculate-and-store-the-euclidian-altitude-between-two-coordinates  \documentclass[border=3pt,tikz]{standalone} \usepackage{physics,bm} \usepackage{tikz,pgfplots} \tikzset{>=latex} % for LaTeX arrow caput \pgfplotsset{compat=1.xiii} \usetikzlibrary{decorations.markings,intersections,calc} \usepackage[outline]{contour} % glow effectually text \usetikzlibrary{angles,quotes} % for moving-picture show (angle labels) \usepackage{xcolor} \colorlet{Ecol}{orange!90!black} \colorlet{EcolFL}{orange!eighty!blackness} \colorlet{Bcol}{blue!xc!black} \tikzstyle{EcolEP}=[blue!80!white] \colorlet{veccol}{green!45!blackness} \tikzstyle{charge+}=[very thin,top color=scarlet!50,bottom colour=red!xc!black,shading bending=20] \tikzstyle{charge-}=[very thin,height color=blue!fifty,bottom color=blueish!80,shading bending=20] \tikzstyle{vector}=[->,thick,veccol] \tikzset{EFieldLineArrow/.fashion={EcolFL,decoration={markings,marking=at position #1 with {\arrow{latex}}},                                  postaction={decorate}},          EFieldLineArrow/.default=0.5} \def\R{1.eight} \def\NE{8} \def\NV{4} \contourlength{1.6pt}    \brainstorm{document}   % POINT Charge +i \begin{tikzpicture}   \foreach \i [evaluate={\angle=(\i-1)*360/\NE;}] in {1,...,\NE}{     \draw[EFieldLineArrow={0.half dozen}] (0,0) -- (\bending:\R);   }   \draw[accuse+] (0,0) circle (7pt) node[black,calibration=0.viii] {$+q$}; \finish{tikzpicture}   % POINT CHARGE -1 \brainstorm{tikzpicture}   \foreach \i [evaluate={\bending=(\i-1)*360/\NE;}] in {1,...,\NE}{     \draw[EFieldLineArrow={0.five}] (\angle:\R) -- (0:0);   }   \draw[charge-] (0,0) circumvolve (7pt) node[black,scale=0.8] {$-q$}; \end{tikzpicture}   % Indicate Charge +1 - equipotential \begin{tikzpicture}   \foreach \i [evaluate={\angle=(\i-one)*360/\NE;}] in {ane,...,\NE}{     \describe[EFieldLineArrow={0.65}] (0,0) -- (\angle:\R);   }   \foreach \i [evaluate={\r=0.9*\R/\i;}] in {1,...,\NV}{     \draw[EcolEP] (0,0) circle (\r);   }   \draw[charge+] (0,0) circle (7pt) node[black,calibration=0.8] {$+q$}; \end{tikzpicture}   % POINT CHARGE -i - equipotential \brainstorm{tikzpicture}   \foreach \i [evaluate={\angle=(\i-1)*360/\NE;}] in {ane,...,\NE}{     \depict[EFieldLineArrow={0.45}] (\bending:\R) -- (0,0);   }   \foreach \i [evaluate={\r=0.ix*\R/\i;}] in {1,...,\NV}{     \draw[EcolEP] (0,0) circle (\r);   }   \draw[accuse-] (0,0) circle (7pt) node[black,scale=0.8] {$-q$}; \end{tikzpicture}   % Signal CHARGE +one - integration \begin{tikzpicture}[scale=1.3]   \def\NE{7}   \def\R{2.0}   \def\a{1.half dozen}   \def\b{i.iv}   \coordinate (O) at (0,0);   \coordinate (P) at (45:0.ix*\R);   \coordinate (L) at ($(P)+(-10:0.twenty*\R)$);   \coordinate (E) at ($(P)+(42:0.four*\R)$);   \foreach \i [evaluate={\ang=15+(\i-1)*360/\NE;}] in {1,...,\NE}{     \draw[EFieldLineArrow={0.65},line width=0.6] (0,0) -- ({0.3*\R+\a*cos(\ang)},{0.25*\R+\b*sin(\ang)});   }   \draw[->] (O) -- (80:1.0*\R) coordinate (A) node[midway,fill=white,inner sep=i] {$r_a$};   \draw[->] (O) -- (5:i.1*\R) coordinate (B) node[midway,fill up=white,inner sep=1] {$r_b$};   \describe[thin,dashed] (A) to[out=ten,in=160] (P) to[out=-10,in=xc] (B);   \draw[vector] (O) -- (P) node[midway,right=nine,beneath=-half-dozen] {$\vb{r}$};   \draw moving-picture show[->,"$\theta$",draw=black,angle radius=11,angle eccentricity=1.5] {angle = 50--P--East};   \describe[vector] (P) -- (L) node[above=2,left=6,below=one,scale=0.9] {$\dd{\bm{\ell}}$};   \draw[vector,Ecol] (P) -- (E) node[above] {$\vb{Eastward}$};   \depict[charge+] (O) circle (five.5pt) node[blackness,scale=0.8] {$+q$}; \terminate{tikzpicture}   % POINT CHARGE +1 - potential \def\NE{seven} \def\a{0.04*\R} \def\R{1.8} \begin{tikzpicture}[scale=one.iii]   \foreach \i [evaluate={\bending=xv+(\i-1)*360/\NE;}] in {1,...,\NE}{     \depict[EFieldLineArrow={0.65},line width=0.6] (0,0) -- (\bending:\R);   }   \draw[accuse+] (0,0) circle (5.5pt) node[black,scale=0.8] {$+q$};   \draw[thin] (90:0.88*\R) coordinate (A) --++ (\a,0) --++ (-two*\a,0) node[above=2,left=-i] {$a$};   \depict[sparse] (90:0.36*\R) coordinate (B) --++ (\a,0) --++ (-2*\a,0) node[in a higher place=iv,left=-one] {$b$};   \draw[->] (A) -- (B) node[midway,above=-5] {\profile{white}{$h$}}; \end{tikzpicture}   % POINT CHARGE -1 - potential \begin{tikzpicture}[scale=1.iii]   \foreach \i [evaluate={\angle=15+(\i-1)*360/\NE;}] in {1,...,\NE}{     \describe[EFieldLineArrow={0.65},line width=0.6] (0,0) -- (\angle:\R);   }   \draw[charge-] (0,0) circle (v.5pt) node[black,scale=0.8] {$-q$};   \draw[sparse] (90:0.88*\R) coordinate (A) --++ (\a,0) --++ (-2*\a,0) node[in a higher place=two,left=-1] {$a$};   \draw[thin] (ninety:0.36*\R) coordinate (B) --++ (\a,0) --++ (-2*\a,0) node[above=4,left=-1] {$b$};   \draw[->] (A) -- (B) node[midway,above=-5] {\contour{white}{$h$}}; \end{tikzpicture}   \end{document}
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