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Unformatted text preview: e to calibrate t he com puter sim ulation program in ord er to translate vector
lengths on the screen to vector m agnitud es that you calculate using your pred iction
equation, w hich are in SI units (assum e Q = 1C). You can use the d ata that you just
collected to d o this. On the com puter, plot the electric field strength in SI units vs. the
electric field in length units that you m easured w ith the ruler. Fit a line to the d at a. If
the fit is good , then you can use the fit equation to convert from electric field lengths on
the screen to electric field m agnitud es in SI units. If it is not good , then you need to go
back and repeat steps 13 above.
N ow , explore the line charge configuration. From the sources pulld ow n m enu select
3D Point Charges. Drag positive charges onto the screen to create a long, uniform line
of charge. H ints: make sure the charges are evenly distributed. Optimize the overall charge
density and placement of the line on the screen in order to be able to obtain good measurements
of electric field vectors. D isplay electric field vectors by clicking at the locations of interest
for this problem , and investigate how the m agnitud e and d irection of the electric field
d epend s on position. Determ ine a m easurem ent plan. M EASUREMEN T
M easure the length and d irection of the electric field vector at varying locations along
each axis of sym m etry. Record the d ata in your notebook. A N ALYSIS
U se the d ata for the follow ing analysis (perform on Excel):
1. Using your calibration equation, convert the lengths of the m easured electric field
vectors prod uced by the com puter sim ulation into electric field strength s in SI units. 43 THE ELECTRIC FIELD FROM A LINE OF CHARGE – 1302Lab2Prob2
2. Using your pred iction equation , w hich is based on Coulom b’s law , calculate the
expected electric field m agnitud es in SI units at the point of interest for your chosen
values of the variable param eter.
3. Com pare your calcu lated electric field strength to that from the com puter sim ulation
on a plot. Also, com p are your pred iction to t he d irection of the field to that from the
com puter sim ulation. CON CLUSION
H ow d id your expected result com pare to your m easured result ? Explain any
d ifferences. From your results, w hich general properties of the electric field d oes the
sim ulation faithfully reprod uce? What is the specific evid ence? 44 PROBLEM #3: ELECTRIC POTEN TIAL
FROM MULTIPLE POIN T CHARGES
You are a m em ber of a team build ing the w orld ’s highest intensity particle accelerator.
In this m achine, charged atom ic nu clei are brought from a very slow speed to alm ost
the speed of light by p assing them through a charged electrod e structure. You nee d to
d eterm ine the effect of these electrod es on the speed of various nuclei. The first step is
to calculate the electric potential that affects the nuclei. Because the charged electrod e
configuration is so com plicated , your team has d ecid ed to use a com puter sim ulation.
Your task is to d eterm ine if the sim ulation results agree w ith the p hysics that you know .
You d ecid e to calculate the electric potential at a point caused by a set of charged objects
that is com plex enou gh to test the sim ulation but sim ple enough to m ake your
calculation possible. The first configuration that you try is a square w ith tw o equal
negatively charged point objects in opposite corners and a positively charged point
object of 1/ 3 the m agnitud e of the negative charges in a thir d corner. You w ill calculate
the electric potential at the rem aining corner of the square and com pare your result to
that of the com puter sim ulation of the sam e configuration.
Instructions: Before lab, read the required reading from the textbook and the laboratory in its
entirety. In your lab notebook, respond to the warm up questions and derive a specific prediction
for the outcome of the lab. During lab, compare your warm up responses and prediction in your
group. Then, work through the exploration, measurement, analysis, and conclusion sections in
sequence, keeping a record of your findings in your lab notebook. It is often useful to use Excel to
perform data analysis, rather than doing it by hand. A t the end of lab, disseminate any electronic
copies of your results to each member of your group.
Read : Tipler & Mosca Sections 23.1 and 23.2 and Exam ple 234. EQUIPMEN T
You w ill use the com p uter program EM Field and a ruler.
If equipment is missing or broken, submit a problem report by sending an email to
l [email protected] . Include the room number and brief description of the
p roblem. WARM UP
1. Draw a schem atic of the charge configuration. Label the objects and their charges.
Show and label all relevant d istances and angles u sing geom etry. Choose an
ap propriate coord inate system .
2. Write d ow n equations for the (scalar) electric potentials at the point of interest caused
by each of the three charged objects using the value of each char ge an...
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This document was uploaded on 02/23/2014 for the course MANAGMENT 2201 at University of Michigan.
 Spring '14

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