[Tex/LaTex] Superscript/subscript fonts different from body font

Question

The following minimal example:

\documentclass{article}
\renewcommand{\familydefault}{\sfdefault}

\begin{document}
10$^5$ and CO$_2$.
\end{document}

produces the following:

The superscript and subscript fonts are different from the body font. Why is this happening, and how can I ensure that those fonts are the same as the body font?

Answer 1

In my view, it's abusing the math environment to use it only to make superscript and subscript numbers in a context that is not math. So I would use \textsuperscript and \textsubscript instead.

\documentclass{article}
\usepackage{fixltx2e}
\renewcommand{\familydefault}{\sfdefault}

\begin{document}
10\textsuperscript{5} and CO\textsubscript{2}.
\end{document}