Electric charge

Basics of electric charge: a silk piece of cloth and a glass rod; and inducing charge in a metal conductor with a ground.

Edit and compile if you like:

% Author: Izaak Neutelings (July 2018)
\documentclass[border=3pt,tikz]{standalone}
\usepackage{tikz}
\tikzset{>=latex} % for LaTeX arrow head
\usepackage{xcolor}
\colorlet{charge+}{red!90!white}
\colorlet{charge-}{blue!80!white}
%\colorlet{metal}{black!5}
%\colorlet{silk}{blue!40!red!10}
%\colorlet{plastic}{yellow!70!red!20}
%\colorlet{glas}{blue!4}
%\usetikzlibrary{positioning,calc}
\def\L{4.5}
\def\W{0.5}
\def\N{8}
\def\angle{45}

\def\chargedRod{
\foreach \i [evaluate={\x=\i*\L/(\N+1);}] in {1,...,\N}{
\path[rotate=\angle] (0,\W/2) --++(\x,0) node[charge+] {+};
}
}

\def\ground{
\foreach \i [evaluate={\y=-0.12*(\i-1); \w=1.1-0.25*\i); \x=-\w/2;}] in {1,...,4}{
\draw[thick] (G) ++ (\x,\y) --++ (\w,0);
}
}

\begin{document}
\Large

% CHARGED INSULATORS BY RUBBING B
\begin{tikzpicture}[scale=0.4]
\def\angle{120}
\def\L{12}
\def\W{1.6}
\def\N{7}

%\draw[very thin,color=gray] (-2,-2) grid (10,10);
\coordinate (SW)  at (   0,  0   ); % SOUTH WEST
\coordinate (WC1) at (   1,  2   );
\coordinate (W1)  at (   1,  4   );
\coordinate (WC2) at (   1,  6   );
\coordinate (W2)  at (   2,  7   );
\coordinate (WC3) at (   3,  8   );
\coordinate (NW)  at (   4, 10   ); % NORTH WEST
\coordinate (NC1) at ( 5.4, 10   );
\coordinate (N1)  at (   6,  9   );
\coordinate (NC2) at ( 6.6,  8   );
\coordinate (N2)  at (   7,  8   );
\coordinate (NC3) at (   8,  8   );
\coordinate (NE)  at (   9,  7   ); % NORTH EAST
\coordinate (EC1) at (   8,  5   );
\coordinate (E1)  at (   8,  4   );
\coordinate (EC2) at ( 8.2,  2   );
\coordinate (E2)  at (   7, -0.5 );
\coordinate (EC3) at ( 6.8, -1.1 );
\coordinate (SE)  at (   6, -1   ); % SOUTH EAST
\coordinate (SC1) at (   5, -0.8 );
\coordinate (S1)  at (   4, -1   );
\coordinate (SC2) at ( 2.7, -1.1 );
\coordinate (S2)  at (   2, -0.5 );
\coordinate (SC3) at ( 1.3,  0   );

% SILK
\draw[silk]
(SW) .. controls (WC1) .. (W1) % SOUTH WEST
.. controls (WC2) .. (W2)
.. controls (WC3) .. (NW) % NORTH WEST
.. controls (NC1) .. (N1)
.. controls (NC2) .. (N2)
.. controls (NC3) .. (NE) % NORTH EAST
.. controls (EC1) .. (E1)
.. controls (EC2) .. (E2)
.. controls (EC3) .. (SE) % SOUTH EAST
.. controls (SC1) .. (S1)
.. controls (SC2) .. (S2)
.. controls (SC3) .. cycle;

% ROD
\coordinate (O) at (15,0);
\draw[glas,rotate around={\angle:(O)}] (O) rectangle ++(\L,\W);

%  \draw[dashed,very thin]
%    (SW) -- (WC1) -- (W1) -- (WC2) -- (W2) -- (WC3) --
%    (NW) -- (NC1) -- (N1) -- (NC2) -- (N2) -- (NC3) --
%    (NE) -- (EC1) -- (E1) -- (EC2) -- (E2) -- (EC3) --
%    (SE) -- (SC1) -- (S1) -- (SC2) -- (S2) -- (SC3) -- cycle;
%
%  \foreach \p in {(SW), (WC1), (W1), (WC2), (W2), (WC3),
%                  (NW), (NC1), (N1), (NC2), (N2), (NC3),
%                  (NE), (EC1), (E1), (EC2), (E2), (EC3),
%                  (SE), (SC1), (S1), (SC2), (S2), (SC3)}{
%    \fill \p circle (2pt) node[above,scale=0.3] {\p};
%  }
\end{tikzpicture}

% CHARGED INSULATORS BY RUBBING B
\begin{tikzpicture}[scale=0.4]
\def\angle{120}
\def\L{12}
\def\W{1.6}
\def\N{7}

\coordinate (SW)  at (   0,  0   ); % SOUTH WEST
\coordinate (WC1) at (   1,  2   );
\coordinate (W1)  at (   1,  4   );
\coordinate (WC2) at (   1,  6   );
\coordinate (W2)  at (   2,  7   );
\coordinate (WC3) at (   3,  8   );
\coordinate (NW)  at (   4, 10   ); % NORTH WEST
\coordinate (NC1) at ( 5.4, 10   );
\coordinate (N1)  at (   6,  9   );
\coordinate (NC2) at ( 6.6,  8   );
\coordinate (N2)  at (   7,  8   );
\coordinate (NC3) at (   8,  8   );
\coordinate (NE)  at (   9,  7   ); % NORTH EAST
\coordinate (EC1) at (   8,  5   );
\coordinate (E1)  at (   8,  4   );
\coordinate (EC2) at ( 8.2,  2   );
\coordinate (E2)  at (   7, -0.5 );
\coordinate (EC3) at ( 6.8, -1.1 );
\coordinate (SE)  at (   6, -1   ); % SOUTH EAST
\coordinate (SC1) at (   5, -0.8 );
\coordinate (S1)  at (   4, -1   );
\coordinate (SC2) at ( 2.7, -1.1 );
\coordinate (S2)  at (   2, -0.5 );
\coordinate (SC3) at ( 1.3,  0   );

% SILK
\draw[silk]
(SW) .. controls (WC1) .. (W1) % SOUTH WEST
.. controls (WC2) .. (W2)
.. controls (WC3) .. (NW) % NORTH WEST
.. controls (NC1) .. (N1)
.. controls (NC2) .. (N2)
.. controls (NC3) .. (NE) % NORTH EAST
.. controls (EC1) .. (E1)
.. controls (EC2) .. (E2)
.. controls (EC3) .. (SE) % SOUTH EAST
.. controls (SC1) .. (S1)
.. controls (SC2) .. (S2)
.. controls (SC3) .. cycle;
\foreach \p in {(4.7,8.4), (6.6,6.8),
(4.1,6.6), (5.8,4.8),
(2.8,5.0), (4.2,3.2), (6.3,2.2),
(2.2,2.6), (3.4,1.0), (5.7,0.0)}{
\node[charge-] at \p {$-$};
}

% ROD
\coordinate (O) at (17,0);
\draw[glas,rotate around={\angle:(O)}] (O) rectangle ++(\L,\W);
\foreach \i [evaluate={\x=\i*\L/(\N+1);}] in {1,...,\N}{
\path[rotate around={\angle:(O)}] (O) ++ (0,\W/2) --++(\x,0) node[charge+] {+};
}

\end{tikzpicture}

% CHARGE BY CONDUCTION A
\begin{tikzpicture}
\draw[rod] (0,0) rectangle ++(\L,\W) node[charge+,midway] {$+\,+\,+\,+\,+\,+\,+\,\,+$};
\draw[rod] (\L+4,0) rectangle ++(\L,\W);
\end{tikzpicture}

% CHARGE BY CONDUCTION B
\begin{tikzpicture}
\draw[rod] (0,0) rectangle ++(\L,\W) node[charge+,midway] {$+\quad\, +\quad\, +\quad\,\, +$};
\draw[rod] (\L,0) rectangle ++(\L,\W) node[charge+,midway] {$+\quad\, +\quad\, +\quad\,\, +$};
\end{tikzpicture}

% CHARGE BY CONDUCTION C
\begin{tikzpicture}
\draw[rod] (0,0) rectangle ++(\L,\W) node[charge+,midway] {$+\quad\, +\quad\, +\quad\,\, +$};
\draw[rod] (\L+4,0) rectangle ++(\L,\W) node[charge+,midway] {$+\quad\, +\quad\, +\quad\,\, +$};
\end{tikzpicture}

% CHARGE BY INDUCTION A
\begin{tikzpicture}
\def\R{0.3*\L}
\coordinate (A) at (0,0);
\coordinate (B) at (2*\R,0);
\draw[metal] (A) circle (\R);
\draw[metal] (B) circle (\R);
\end{tikzpicture}

% CHARGE BY INDUCTION B
\begin{tikzpicture}
\def\R{0.3*\L}
\def\N{6}
\coordinate (A) at ({1.01*\R+\L*cos(\angle)},{0.6*\L*sin(\angle)});
\coordinate (B) at ({3.01*\R+\L*cos(\angle)},{0.6*\L*sin(\angle)});
\chargedRod
\draw[metal] (A) circle (\R);
\draw[metal] (B) circle (\R);
\foreach \i [evaluate={\a=170-30*(\N-1)/2+30*(\i-1);}] in {1,...,\N}{
\path (A) --++ (\a:0.8*\R) node[charge-] {$-$};
\path (B) --++ (\a-180:0.8*\R) node[charge+] {$+$};
}
\end{tikzpicture}

% CHARGE BY INDUCTION C
\begin{tikzpicture}
\def\R{0.3*\L}
\def\N{6}
\coordinate (A) at ({1.01*\R+\L*cos(\angle)},{0.6*\L*sin(\angle)});
\coordinate (B) at ({3.21*\R+\L*cos(\angle)},{0.6*\L*sin(\angle)});
\chargedRod
\draw[metal] (A) circle (\R);
\draw[metal] (B) circle (\R);
\foreach \i [evaluate={\a=170-30*(\N-1)/2+30*(\i-1);}] in {1,...,\N}{
\path (A) --++ (\a:0.8*\R) node[charge-] {$-$};
\path (B) --++ (\a-180:0.8*\R) node[charge+] {$+$};
}
\end{tikzpicture}

% CHARGE BY INDUCTION B
\begin{tikzpicture}
\def\R{0.3*\L}
\def\N{6}
\coordinate (A) at (0,0);
\coordinate (B) at (3.0*\R,0);
\draw[metal] (A) circle (\R);
\draw[metal] (B) circle (\R);
\foreach \i [evaluate={\a=-10+360*\i/\N;}] in {1,...,\N}{
\path (A) --++ (\a:0.75*\R) node[charge-] {$-$};
\path (B) --++ (\a:0.75*\R) node[charge+] {$+$};
}
\end{tikzpicture}

% CHARGE BY INDUCTION & GROUNDING A
\begin{tikzpicture}
\def\R{0.35*\L}
\draw[metal] (0,0) circle (\R);
\end{tikzpicture}

% CHARGE BY INDUCTION & GROUNDING B
\begin{tikzpicture}
\def\R{0.35*\L}
\def\N{6}
\def\h{0.6*\L*sin(\angle)}
\coordinate (O) at ({1.01*\R+\L*cos(\angle)},{\h});
\chargedRod
\draw[metal] (O) circle (\R);
\foreach \i [evaluate={\a=170-30*(\N-1)/2+30*(\i-1);}] in {1,...,\N}{
\path (O) --++ (\a:0.8*\R) node[charge-] {$-$};
\path (O) --++ (\a-180:0.8*\R) node[charge+] {$+$};
}
\end{tikzpicture}

% CHARGE BY INDUCTION & GROUNDING C
\begin{tikzpicture}
\def\R{0.35*\L}
\def\N{6}
\def\h{0.6*\L*sin(\angle)}
\coordinate (O) at ({1.01*\R+\L*cos(\angle)},{\h});

% ROD & SPHERE
\chargedRod
\draw[metal] (O) circle (\R);
\foreach \i [evaluate={\a=170-30*(\N-1)/2+30*(\i-1);}] in {1,...,\N}{
\path (O) --++ (\a:0.8*\R) node[charge-] {$-$};
\path (O) --++ (\a-180:0.8*\R) node[charge+] {$+$};
}

% GROUND
\draw[thick] (O) ++ (\R,0) --++ (0.2*\R,0) coordinate (P) --++ (0,{-\h}) coordinate (G);
\node[below=2,right=15] at (G) {ground};
\ground

% ELECTRONS
\draw[->,thick] (P) ++ (0.1*\R,-0.45*\R)
.. controls ++(0.01*\R,0.61*\R) .. ++(-0.2*\R,0.6*\R) node[charge-,right=4,above] {$-$};
\node[charge-,below=4,right=8,align=center] at (P) {$-$\\$-$\\$-$};

\end{tikzpicture}

% CHARGE BY INDUCTION & GROUNDING D
\begin{tikzpicture}
\def\R{0.35*\L}
\def\N{6}
\def\h{0.6*\L*sin(\angle)}
\coordinate (O) at ({1.01*\R+\L*cos(\angle)},{\h});

% ROD & SPHERE
\chargedRod
\draw[metal] (O) circle (\R);
\foreach \i [evaluate={\a=170-30*(\N-1)/2+30*(\i-1);}] in {1,...,\N}{
\path (O) --++ (\a:0.8*\R) node[charge-] {$-$};
}

% GROUND
\draw[thick] (O) ++ (\R,0) --++ (0.2*\R,0) --++ (0,{-\h}) coordinate (G);
\node[below=2,right=15] at (G) {ground};
\ground
\end{tikzpicture}

% CHARGE BY INDUCTION & GROUNDING E
\begin{tikzpicture}
\def\R{0.35*\L}
\def\N{6}
\def\h{0.6*\L*sin(\angle)}
\coordinate (O) at ({1.01*\R+\L*cos(\angle)},{\h});

% ROD & SPHERE
\chargedRod
\draw[metal] (O) circle (\R);
\foreach \i [evaluate={\a=170-30*(\N-1)/2+30*(\i-1);}] in {1,...,\N}{
\path (O) --++ (\a:0.8*\R) node[charge-] {$-$};
}

% GROUND
\draw[thick] (O) ++ (1.2*\R,0) --++ (0,{-\h}) coordinate (G);
\node[below=2,right=15] at (G) {ground};
\ground
\end{tikzpicture}

% CHARGE BY INDUCTION & GROUNDING F
\begin{tikzpicture}
\def\R{0.35*\L}
\def\N{6}
\def\h{0.6*\L*sin(\angle)}
\coordinate (O) at ({1.01*\R+\L*cos(\angle)},{\h});

% ROD & SPHERE
\draw[metal] (O) circle (\R);
\foreach \i [evaluate={\a=-10+360*\i/\N;}] in {1,...,\N}{
\path (O) --++ (\a:0.75*\R) node[charge-] {$-$};
}

\end{tikzpicture}

\end{document}