1

Draw a sphere with radius with TikZ. According to the figure

enter image description here

20

It is always hard to get answers to questions on the form "draw this for me" without showing any effort your self. Next time try to start a solution and add a MWE to your question, then you have much higher chance of getting someone to dig into your problem.

Here I guess the problem is the equator, where you can use \arc with different x- and y-radius.

\documentclass[border=5mm]{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
  \shade[ball color = gray!40, opacity = 0.4] (0,0) circle (2cm);
  \draw (0,0) circle (2cm);
  \draw (-2,0) arc (180:360:2 and 0.6);
  \draw[dashed] (2,0) arc (0:180:2 and 0.6);
  \fill[fill=black] (0,0) circle (1pt);
  \draw[dashed] (0,0 ) -- node[above]{$r$} (2,0);
\end{tikzpicture}
\end{document}

enter image description here

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