\documentclass{standalone}
\usepackage[american]{circuitikz}
\usepackage{graphicx}
\usepackage{mathrsfs} 
\usepackage{latexsym,amssymb,amsmath}
\newcommand{\equal}{=}
\begin{document}
	
			\begin{circuitikz}
				\draw (0,2) to [V,l_=$\mathscr{F}\equal NI$] (0,0) 
				(0,0) to [R,l^=$\mathscr{R}_{g}$, v_<=$\mathscr{F}_1$, color=green] (4,0)
				(0,2) to [R,l_=$0.5\mathscr{R}_{s}$, v^>=$\mathscr{F}_2$, color=blue] (4,2)
				(4,2) -- (4,0);
			\node (phi) at (3.0,0.25) {$\phi$};
			\draw[-stealth]  (3.25,1.75) to [bend left=90] (phi); 
			\end{circuitikz}
\end{document}