\documentclass[11pt]{article}
\usepackage[a4paper,margin=18mm]{geometry}
\usepackage{tikzphysics}
\pagestyle{empty}
\begin{document}
\section*{Polar boundaries and the true area centroid}
\begin{center}
\begin{tikzpicture}[>=latex,font=\small]
 \node[polar element,element inner radius=3cm,element outer radius=3.2cm,
  element start angle=-15,element delta angle=30] (P) {};
 \foreach \p in {0,50,100}{
  \fill (P.outer-\p) circle (1.5pt);
  \draw (P.outer-\p)--++(.6,0) node[right] {\p};
 }
 \fill (P.centroid) circle (1.5pt);
 \draw[<-] (P.centroid)--++(-.8,.6) node[above left] {area centroid};
 \node[below=14pt] at (P.south) {Large radii: $r=3\,\mathrm{cm}$, $r+d\!r=3.2\,\mathrm{cm}$};
\end{tikzpicture}
\end{center}
The outer family follows the arc counterclockwise. The start and end families
run from the inner radius to the outer radius. A sector's placement centre is
the circle centre; its area centroid is a separate anchor.
\begin{center}
\begin{tikzpicture}[>=latex,font=\small]
 \node[polar element,element inner radius=1cm,element radial thickness=3mm,
  element start angle=-20,element delta angle=70,rotate=35] (R) {};
 \foreach \p/\x/\y in {0/.1/-.5,50/.9/-.75,100/1.7/-.5}{
  \fill (R.start-\p) circle (1.5pt);
  \draw (R.start-\p)--(\x,\y) node[below] {\p};
 }
 \node[differential ring,element inner radius=1cm,element radial thickness=2mm] (D) at (6,0) {};
 \foreach \p/\pos in {0/right,25/above,50/left,75/below}{
  \fill (D.outer-\p) circle (1.5pt);
  \node[\pos] at (D.outer-\p) {\p};
 }
 \fill (D.centroid) circle (1.5pt);
 \node[below=14pt] at (R.south) {Rotated radial edge: inner to outer};
 \node[below=14pt] at (D.south) {Full ring: centroid at its centre};
\end{tikzpicture}
\end{center}

\clearpage
\section*{Percentage coordinates on projected rims}
\begin{center}
\begin{tikzpicture}[>=latex,font=\small]
 \pic (S) {sphere slice diagram};
 \foreach \p/\pos in {0/right,25/above,50/left,75/left}{
  \fill (S-disk-rim-\p) circle (1.5pt);
  \node[\pos] at (S-disk-rim-\p) {\p};
 }
 \pic (C) at (7,0) {cylinder slice diagram};
 \foreach \p/\x/\y in {0/.4/.7,25/0/.5,50/-.4/.2,75/0/-.6}{
  \fill (C-slice-top-rim-\p) circle (1.5pt);
  \draw (C-slice-top-rim-\p)--++(\x,\y) node[above] {\p};
 }
\end{tikzpicture}
\end{center}
Rim percentages run counterclockwise from the rightmost point of the displayed
ellipse. They use pic coordinates, such as \texttt{(C-slice-top-rim-25)}.
\begin{center}
\begin{tikzpicture}[>=latex,font=\small]
 \pic (H) {cylinder shell diagram};
 \foreach \p in {0,50,100}{
  \fill (H-height-\p) circle (1.5pt);
  \node[left=2pt] at (H-height-\p) {\p};
 }
 \pic[rotate=20,scale=.8,transform shape] (K) at (7,0) {cone slice diagram};
 \foreach \p/\x/\y in {0/.3/.7,25/-.8/.7,50/-.5/.1,75/0/-.7}{
  \fill (K-slice-top-rim-\p) circle (1.5pt);
  \draw (K-slice-top-rim-\p)--++(\x,\y) node[above] {\p};
 }
\end{tikzpicture}
\end{center}
Cylinder height coordinates measure the axial height between circle centres.
Cone rim coordinates follow the unequal top and bottom slice radii, including
under rotation and scaling. The highlighted slice thickness is schematic.

\clearpage
\section*{Native TikZ stroke and arrow defaults}
\begin{center}
\begin{tikzpicture}[>=latex,font=\small]
 \node[draw,minimum width=2cm,minimum height=1cm] (A) at (0,0) {TikZ node};
 \node[conduction slab,conduction width=2cm,conduction height=1cm] (B) at (4,0) {thermal};
 \node[rectangular element,element width=2cm,element height=1cm,pattern=none] (C) at (8,0) {element};
 \draw[->] (A.south)--++(0,-1.2);
 \draw[force] (B.south)--++(0,-1.2);
 \draw[->] (C.south)--++(0,-1.2);
 \node[heat engine] (E) at (0,-4) {$E$};
 \node[radiating body,radiation ray length=.5cm] at (4,-4) {$T$};
 \node[plane mirror,mirror height=2cm] at (8,-4) {};
\end{tikzpicture}
\end{center}
No line width is specified in this picture. The ordinary TikZ node, package
nodes, force arrow, and heat-transfer rays share the document's native stroke
width and latex arrow convention. Colors default to black and white. Authors
can style their document using ordinary TikZ options and the package's
\texttt{every ...} hooks.
\end{document}