\documentclass[11pt]{article}
\usepackage{fig4tex}
\begin{document}

% 1. Definition of characteristic points

\figinit{.8cm}

%Axes.
\figpt 1:(0,0)
\figpt 2:(2,0)
\figpt 3:(0,2)
\figvectC 0 (6,0)
\figpttra 1:=1 /1, 0/
\figpttra 2:$x$=2 /1, 0/
\figpttra 3:$y$=3 /1, 0/

%Antenne.
\def\ray{2}

\figpt 5:(0,\ray)
\figpt 6:(0,0)
\figpt 7:(0,-\ray)
\figpt 8:(\ray,0)

\def\ang{35}
\figptrot 9:=7 /6,\ang/
\def\angi{20}
\def\angii{55}
\figptrot 10:=7 /6,\angi/
\figptrot 11:=7 /6,\angii/
\def\rap{.4}
\figpthom 12:=7 /6,\rap/
\figpthom 13:=9 /6,\rap/
\figptbary 14:[12,13;1,1]

% 2. Creation of the graphical file

\figdrawbegin{}

%Axes.
\figdrawarrow[1,2]
\figdrawarrow[1,3]

%Anneau.
\figdrawline[5,7]
\figdrawarccircP 6;\ray[8,5]

%Courant.
\figset arrowhead(fillmode=yes)
\figdrawarrowcircP 6 ; \ray [7,8]
\figset arrowhead(fillmode=no)

%dl.
\figdrawline[6,9]
\figset (width=1.5)
\figdrawarrowcircP 6 ; \ray [10,11]
\figset (width=default)\figset arrowhead(length=0.3)
\figdrawarrowcircP 6 ; 1 [12,13]

\figdrawend

% 3. Writing text on the figure

\def\dist{3pt}
\figvisu{\figBoxA}{{\sc Fig. 7}\ --\ Demi-anneau }{%
\figwritene 2:(\dist)
\figwriten 3:(\dist)
\figwriten 5:$B$(\dist)
\figwrites 7:$A$(\dist)
\figwritee 8:$I/2$(\dist)
\figwritese 9:$\overrightarrow{dl}$(\dist)
\figwriten 9:$P$(6pt)
\figwrites 14:$\theta$(8pt)
}
\box\figBoxA
\end{document}