How to share a one column figure with two column text on same page

Question

I am writing an article that is composed of a two column body. But on one page, I want a figure that takes up both columns at the top and below I want to continue writing in two column text.

So far I have,

\newpage
\onecolumn
\subsection{Pumped Hydro}

\begin{figure}[h!]
\includegraphics[scale=0.75]{operatingprincipal.jpg}
\caption{Pumped Hydro}
\end{figure}
\twocolumn
 {text goes here}

what happens here is the text continues on the next page, leaving about 3/4 of a page of blank space below the figure. Any help would be appreciated.

Answer 1

For a two column figure you want the * form. remove the \onecolumn and \twocolumn and use

\begin{figure*}
\includegraphics[scale=0.75]{operatingprincipal.jpg}
\caption{Pumped Hydro}
\end{figure*}

(don't use [h!] on figures as the main effect of that is to prevent the figure being placed in any available float area and so go to the end of the document. LaTeX issues a warning and changes it to [!ht] to at least allow top floats but it still leaves float pages disabled.

As two column floats come at the earliest on the page after they appear in the source you may need to move the location of this in your source document.