I was taught that if you want to change the direction of a three phase rotating machine that is rotating in forward direction, you interchange the phases. Since the phases has the same features (voltage and current), what is responsible for making the machine to rotate in reverse direction, when the phases are interchanged?


Question: Using pstool with beamer
Answer: pstool package uses the preamble of main document class(in your Q it is beamer) to build the pdf figures during the underhood auxiliary processing (latex-dvips-ps2pdf) of  .eps figure and psfrag commands. So to get a circle.pdf figure without navigation bar add 

\setbeamertemplate{navigation symbols}{} 


in the preamble after \documentclass{beamer}as shown in
How to get rid of navigation symbols in beamer? and compile with pdflatex -shell-escape gives



Once you have all pdf figures are generated via auxiliary processing.  Set the option process=none instead of process=all and comment out the only line  like this 
%\setbeamertemplate{navigation symbols}{} to process beamer slides with figures (navigation bar less) and finally you will get navigation bar on main beamer slides.

Note: \EndPreamble can be used to limit the preamble used for auxiliary processing and thereby speed it up. More details refer pstool documentation