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Unformatted text preview: nt magnitudes of charge. What range of charge values allows you to
accurately measure the length of the electric field vector at all points on the screen?
Where is a good place to put the configuration in order to get a larger number of
To check whether or not you get the correct behavior of the electric field from a point
charge do the following:
1. Pick a useful charge value and determine several locations at different distances r
from the center of the single point charge. (Hint: Choose your locations at regular
intervals.) At each location, measure r and the length of the electric field vector. In
your notebook, record the data and sketch a plot of the vector length as a function of r.
2. Now, calculate what Coulomb’s law predicts and sketch the values for the field
strength vs. distance (r) on the same graph.
3. Compare the shape of the graph to that based on the Coulombs’ law and record your
You have to calibrate the computer simulation program in order to translate vector
lengths on the screen to vector magnitudes that you calculate using your prediction
equation, which are in SI units (assume Q = 1C). You can use the data that you just
collected to do this. On the computer, plot the electric field strength in SI units vs. the
electric field in length units that you measured with the ruler. Fit a line to the data. If
the fit is good, then you can use the fit equation to convert from electric field lengths on
the screen to electric field magnitudes in SI units. If it is not good, then you need to go
back and repeat steps 1-3 above.
Now, explore the line charge configuration. From the sources pull-down menu select
3D Point Charges. Drag positive charges onto the screen to create a long, uniform line
of charge. Hints: 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. Display electric potential values by clicking at the locations of
interest for this problem, and investigate how the electric potential depends on position.
Determine a measurement plan. MEASUREMENT
Measure the electric potential at varying locations along each axis of symmetry. Record
the data in your notebook. 51 ELECTRIC POTENTIAL FROM A LINE OF CHARGE – 1302Lab2Prob4 ANALYSIS
Use the data for the following analysis (perform on Excel):
1. Using your calibration equation, convert the electric potential values produced by the
computer simulation into electric field strengths in SI units.
2. Using your prediction equation, which is based on Coulomb’s law, calculate the
expected electric potential in SI units along each axis of symmetry.
3. Compare the calculated potential to that from the computer simulation on a plot for
both data sets (2 axes of symmetry). Include uncertainties. Without them, the results
are nearly meaningless. CONCLUSION
How did your expected result compare to your measured result? Explain any
differences. From your results, which general properties of the electric potential does
the simulation faithfully reproduce? What is the specific evidence?
Where is the electric potential defined to be zero? Is this consistent with your results?
Compute the derivative with respect to the distance from the rod along each axis of
symmetry. How do these compare with the magnitude of the electric fields from the
earlier lab Electric Field from a Line of Charge? Is this consistent with what you know
about the relationship between electric field and electric potential? Why or why not? 52 CHECK YOUR UN D ERSTAN D IN G LAB 2: ELECTRIC FIELD S AN D ELECTRIC POTEN TIALS
For each of the charge configu rations below , find the electric field and the electric p otential at the p oint
m arked w ith the “?”. C onfigu ration 2 C onfigu ration 1 C onfigu ration 4 C onfigu ration 3 53 CHECK YOUR UN D ERSTAN D IN G LAB 2: ELECTRIC FIELD S AN D ELECTRIC POTEN TIALS 54 TA Name: PHYSICS 1302 LABORATORY REPORT
Name and ID#:
Date performed: Day/Time section meets: Lab Partners' Names: Problem # and Title:
Lab Instructor's Initials:
Grading Checklist Points LABORATORY JOURNAL:
(individual predictions and warm-up completed in journal before each lab session)
(measurement plan recorded in journal, tables and graphs made in journal as data is
collected, observations written in journal) PROBLEM REPORT:*
(clear and readable; logical progression from problem statement through conclusions;
pictures provided where necessary; correct grammar and spelling; section headings
provided; physics stated correctly)
DATA AND DATA TABLES
(clear and readable; units and assigned uncertainties clearly stated)
(results clearly indicated; correct, logical, and well-organized calculations with
uncertainties indicated; scales, labels and uncertainties on graphs; physics stated correctly)
(comparison to prediction & theory discussed with physics stated correctly ; possible
sources of uncertainties identified; attention called to experimental problems)
TOTAL(incorrect or missing statement of physics will result in a maximum of 60% of the
total points achieved; incorrect grammar or spelling will result in a maximum of...
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This document was uploaded on 02/23/2014 for the course MANAGMENT 2201 at University of Michigan.
- Spring '14