Synchronized manual with one of Justin

Updated source was located at
located at https://bitbucket.org/jrsteven/phys251_manual/src/master/

1 files changed, 18 insertions, 15 deletions

diff --git a/emratio.tex b/emratio.tex
index 42d6630..af4df4b 100644
--- a/emratio.tex
+++ b/emratio.tex
@@ -123,7 +123,6 @@ between the cathode and the anode. The grid is held positive with respect to
 the cathode and negative with respect to the anode. It helps to focus the
 electron beam.
 
-
 The Helmholtz coils of the $e/m$ apparatus have a radius and separation of
 $a=15$~cm. Each coil has $N=130$~turns. The magnetic field ($B$) produced by
 the coils is proportional to the current through the coils ($I_{hc}$) times
@@ -135,6 +134,15 @@ scale, you can measure the radius of the beam path without parallax error. The
 cloth hood can be placed over the top of the $e/m$ apparatus so the experiment
 can be performed in a lighted room.
 
+\subsection*{Pasco High Voltage Power Supply}
+
+The Pasco High Voltage Power Supply in Fig.~\ref{hv_power.fig} provides up to 500 V DC accelerating voltage to the electrodes in the e/m tube, which is measured on the voltmeter shown in Fig.~\ref{emfig3}.  The electron gun heater is also powered by this supply using the right panel, which should be set to a maximum of 6 V AC using the dial on the supply.
+
+\begin{figure}[h]
+\centering
+\includegraphics[width=0.7\columnwidth]{./pdf_figs/eoverm_powersupply.jpeg}
+\caption{\label{hv_power.fig} Pasco High Voltage Power Supply.}
+\end{figure}
 
 \subsection*{Safety}
 You will be working with high voltage. Make all connections when power is off.
@@ -180,7 +188,7 @@ For each measurement record:
 \item[Accelerating voltage $V_a$]
 \item[Current through the Helmholtz coils $I_{hc}$]
 \end{description}
-Look through the tube at the electron beam. To avoid parallax errors, move your head to align one side the electron beam ring with its reflection that you can see on the mirrored scale. Measure the radius of the beam as you see it, then repeat the measurement on the other side, then average the results. Each lab partner should repeat this measurement, and estimate the uncertainty. Do this silently and tabulate results. After each set of measurements (e.g., many values of $I_{hc}$ at one value of $V_a$) compare your results. This sort of procedure helps reduce group-think, can get at some sources of systematic errors, and is a way of implementing experimental skepticism. 
+Look through the tube at the electron beam. To avoid parallax errors, move your head to align one side of the electron beam ring with its reflection that you can see on the mirrored scale. Measure the radius of the beam as you see it, then repeat the measurement on the other side, then average the results. Each lab partner should repeat this measurement, and estimate the uncertainty. Do this silently and tabulate results. After each set of measurements (e.g., many values of $I_{hc}$ at one value of $V_a$) compare your results. This sort of procedure helps reduce group-think, can get at some sources of systematic errors, and is a way of implementing experimental skepticism. 
 
 \item Repeat the radius measurements for at least 4 values of $V_a$ and for each $V_a$ for 5-6 different values of the magnetic field.
 
@@ -214,21 +222,16 @@ cause the radius to be measured as smaller than it should be.
 
 \subsection*{Calculations and Analysis:}
 \begin{enumerate}
- \item Calculate $e/m$ for each of the
-readings using Eq. \ref{emeq7}.    NOTE: Use MKS units for
-calculations.
+ \item Calculate $e/m$ for each of the readings using Eq. \ref{emeq7} and determine the uncertainty on $e/m$ based on your uncertainty estimates for those readings.  NOTE: Use MKS units for calculations.
 \item  For each of the four $V_a$ settings calculate the mean
-$<e/m>$, the standard deviation $\sigma$ and {\bf the standard error in the
-mean $\sigma_m$.}
+$<e/m>$ and the standard deviation $\sigma$.
 Are these means consistent with one another sufficiently that you can
-combine them ?  [Put quantitatively, are they within $2 \sigma$ of each
-  other ?]
-\item Calculate the {\bf grand mean} for all $e/m$ readings, its
-standard deviation $\sigma$  {\bf and the standard error in the grand mean
-$\sigma_m$}.
-\item Specify how this grand mean compares to the accepted value, i.e., how many $\sigma_m$'s is it from the accepted value ?
+combine them?  [Put quantitatively, are they within $2 \sigma$ of each
+  other?]
+%\item Calculate the {\bf grand mean} for all $e/m$ readings and its standard deviation $\sigma$.  
+%\item Specify how this grand mean compares to the accepted value, i.e., how many $\sigma$'s is it from the accepted value ?
 
-\item  Finally, plot the data in the following way which should, ( according to Eq. \ref{emeq7}), reveal a linear relationship: plot  $V_a$ on the abscissa [x-axis] versus  $r^2 B^2/2$ on the ordinate [y-axis]. The uncertainty in $r^2 B^2/2$ should come from the standard deviation of the different measurements made by your group at the fixed $V_a$. The optimal slope of this configuration of data should be $<m/e>$. Determine the slope from your plot and its error by doing a linear fit. What is the value of the intercept? What should you expect it to be?
+\item Finally, plot the data in the following way which should, ( according to Eq. \ref{emeq7}), reveal a linear relationship: plot  $V_a$ on the abscissa [x-axis] versus  $r^2 B^2/2$ on the ordinate [y-axis]. The uncertainty in $r^2 B^2/2$ should come from the standard deviation of the different measurements made by your group at the fixed $V_a$. The optimal slope of this configuration of data should be $<m/e>$. Determine the slope from your plot and its error by doing a linear fit, and compare the slope parameter to the accepted value for $<m/e>$. What is the value of the intercept? What should you expect it to be?
 
 \item Comment on which procedure gives a better value of $<e/m>$ (averaging or linear plot).
 \end{enumerate}
@@ -250,7 +253,7 @@ where $\mu_0$ is the magnetic permeability constant, $I$ is the total electric c
 This configuration provides very uniform magnetic field along the common axis of the pair, as shown in Fig.~\ref{emfig4}. The correction to the constant value given by Eq.(\ref{emeq_apx}) is proportional to $(x/a)^4$ where $x$ is the distance from the center of the pair. However, this is true only in the case of precise alignment of the pair: the coils must be parallel to each other!
 \begin{figure}[h]
 \centering
-\includegraphics[width=0.6\columnwidth]{./pdf_figs/emratioFig4}
+\includegraphics[width=0.7\columnwidth]{./pdf_figs/emratioFig4}
 \caption{\label{emfig4}Dependence of the magnetic field produced by a Helmholtz
 coil pair $B$ of the distance from the center (on-axis) $x/a$. The magnetic
 field is normalized to the value $B_0$ in the center.}