\section{EC-6 Magnetism}
\subsection*{EC-6a~~Lens's Law}

\noindent OBJECTIVES: \begin{enumerate} \epind{
\item\vspace*{-.08in} {To observe the eddy currents induced by the magnetic field 
in a moving conductor.}
\item\vspace*{-.08in} {To follow how the eddy current intensity depends on the shape of
the conductor.}  
} \end{enumerate}

\hspace*{.3in} \framebox[5.2in]{\parbox[b]{5in}{\smallskip {\em YOU NEED TO KNOW:} 
You must understand and be able to use the Right Hand Rule in order to 
determine the direction and sense of the forces involved. 
\smallskip }}\smallskip 

\noindent
APPARATUS: \latex{\vspace*{.00in}}   \\ 
\pind{ A Permanent Magnet; four different padle penduli; 
two small red and green magnets.} 
\begin{figure}[h] \centering 
\latex{\includegraphics[height=6.5cm]{figs/l104/fec6a-1.eps}}
\html{\includegraphics[height=7cm]{figs/l104/fec6a-1.eps}}
\vspace*{-.08in}
\caption {The magnet and the paddle pendulum}
\end{figure}
\vspace*{-.15in}\hspace*{.03in}

\noindent PROCEDURE I:  (10 min) \\ 
\vspace*{-.15in}\hspace*{.03in}
\parbox{0.5\linewidth}{
\begin{enumerate}
\item [1.]\vspace*{-.11in} Using one of the small magnets determine the direction of the
magnetic field between the jaws of the permanent magnet.
\item [2.]\vspace*{-.11in} Observe and describe the behaviour of the four penduli when dropped
between the jaws of the permanent magnet.
\item [3.]\vspace*{-.11in} Reverse the magnet. Observe and describe the behaviour of 
two penduli when dropped
between the jaws of the permanent magnet.
\item [4.]\vspace*{-.11in} Set pendulum \#1 between the jaws of the magnet. Move the
magnet  rapidly in a direction parallel to the pendulum plate 
i.e.~{\em without touching} 
jaws. Describe what happens.
\end{enumerate}
}\hspace*{.03in}
\parbox{0.5\linewidth}{
%\begin{figure}[h] \centering 
\latex{\includegraphics[height=6cm]{figs/l104/fec6a-2.eps}}
\html{\includegraphics[height=8cm]{figs/l104/fec6a-2.eps}} \\
\hspace*{0.00in}Figure 2: Paddle moves in the $+y$ direction
\vspace*{-.08in}
%\caption{The setup}
%\end{figure}
}
\newpage


\noindent QUESTIONS:   
\begin{enumerate} \epind{
\item[Q1]\vspace*{-.08in} Use the right hand rule to determine the motion of electrons at 
the moment when pendulum \# 4 enters the magnetic field  region. Is it from 
A to B? Or from B to A? 
\item[Q2]\vspace*{-.08in} What is the direction of the current flowing in the pendulum?  
Is it from 
A to B? Or from B to A?
\item[Q3]\vspace*{-.08in}  Use the right hand rule to determine the direction of the force
exerted on the current that flows in the arm of the pendulum by the magnetic 
field. Is it along the positive or the negative y axis?}
\end{enumerate}
%\end{document}
%\end
