Subscript in beamer class using frames and equations

Question

\documentclass{beamer}
\usepackage[latin1]{inputenc}
\usepackage{textpos}
\usetheme{CambridgeUS}
\usepackage[british,UKenglish,USenglish,english,american]{babel}
\begin{document}
 \begin{frame}
  \begin{equation}
    Energy Factor_A_big/small 
  \end{equation}
 \end{frame}
\end{document}

What I am trying to achieve there is to get a space in between Energy and Factor, secondly. I want A to be a subscript of Energy Factor and big/small to be a subscript of A.

What is the mistake I'm doing?

Answer 1

I think it is quite nasty, but Energy~Factor_{A_{big/small}} does the job. In my opinion \text{Energy Factor}_{A_\text{big/small}} is way better.