Physics III Lab

Spring Term 2014

General Information

Instructor:    Galen C. Duree Jr., PhD

Office:    Room DL102                       Phone:    872-6025                                 Box:    182


Office Hours:      9:15 AM - 11:00 AM  Th  &  4:20 PM - 5:30 PM M T  Th F

The second series of experiments for the Physics III laboratories will be held in CL117 this week.  The experiments are entitled "Faraday's Law" and the description can be found in the lab manual, beginning on page 131.  The lab reports will be due by 5:30 PM in the green bin outside my office, one week from the date that you perform the experiments.

Section 51 will meet at 8:05 AM on Monday, April 20, 2015.

Section 52 will meet at 8:05 AM on Tuesday, April 14, 2015.

Section 53 will meet at 8:05 AM on Friday, April 17, 2015.


For this lab, you will be evaluating a couple of induction models for the given coil arrangement.  The first model is the induced emf is proportional to ΔV/Δt for a saw-tooth input function.  Take data for at least 5 different values of ΔV/Δt.  The uncertainty in the induced emf should be estimated from the readings on your oscilloscope.  Before you make the graph for this situation, make sure that you propagate the uncertainty for the ΔV/Δt values since you should have an uncertainty with ΔV and a separate one for Δt.  Make a graph of induced emf vs. ΔV/Δt, fit a trend line to the data and place error bars on all of the points.  If a majority of the points' error bars cross the trend line, the model is appropriate; if they do not, then the model is not appropriate for your situation.

The second model is the induced emf is proportional to the angular frequency for a sinusoidal input function.  Take data of the induced emf for at least 5 different values of frequency.  Calculate the angular frequencies and determine the appropriate uncertainties.  Make a graph of induced emf vs. linear frequency (f) OR angular frequency (ω), fit a trend line to the data and place error bars on all of the points.  If a majority of the points' error bars cross the trend line, the model is appropriate; if they do not, then the model is not appropriate for your situation.


Lab #1:

For this lab, you will be evaluating a model for the force between parallel, current-bearing, conductors.  After you have taken your data of force vs. current (there should be at least five different masses used), make a graph of the force (weight) vs. the current SQUARED.  The current value that you use should be the average of the four current values that you obtained for each mass.  The uncertainty in the current is the standard deviation of the four currents.  The standard deviation is the uncertainty that you should use for the current - propagate the uncertainty to find the uncertainty in I2.  Include error bars on each of the points on your graph and fit a trend line to the data.  If a majority of the points' error bars cross the trend line, the model is appropriate for your situation.  If a majority of the points' error bars do not cross the trend line, then the model is not appropriate.  Using the slope of the line (with uncertainty), compare this experimental C value to the theoretical constant value (calculated from Equation 4-9).  Make sure that you propagate the uncertainties!  Do this for both the single spacer and the double spacer arrangements.  If you were not able to get enough points (3 or more masses) with the double spacer, then you only need to do the analysis for the single spacer.  Please make sure that you explain why you did not do the analysis for the double spacer if you do not have enough data points.

Download a copy of the Error Analysis Worksheet

The second experiments will be performed during the week after Spring Break.

Lab Report Format

A complete lab report must have the following sections:

Make sure that you address the specific tasks that I give you!  If you perform great analysis and have insightful conclusions, but do not address the tasks that I give you, do NOT expect a very good grade on your report - no matter how much effort you put into it!

Do not forget to update your Table of Contents and to number the pages in your lab notebook!

The first page of your report must have a title, the name of the P.I. (explicitly indicate who was the P.I.), the name of the lab assistant, and the date that the report was turned in (not the date that you performed the experiment!).

*Abstract - a BRIEF description of what you were investigating, how you conducted the experiment and your conclusions based on your experience.  Try to write the abstract with 150 words or less, but still communicate important information.  The abstract should not be a discussion of what you are going to do in the lab.  The abstract cannot be written before you have analyzed your data.  In the lab notebook, skip a page or two so that you can write this in at the beginning of the report after you have analyzed your data.

Introduction - a discussion about any details that you think would help someone perform the experiment.  This should include a discussion about the model or the method selected for performing the tests.  If you use models (equations) in your analysis, list the models in this section and describe what each of the variables represent.  Do NOT include formulas for calculating averages and standard deviations.

*Procedure - a detailed description of what you did in the lab.  At the beginning of this section, place the date and the time that you began the experiment.  This section must include a schematic, detailing how things were connected, where appropriate.  The raw data must appear in this section immediately following the description about how the data was taken.   A person must be able to read your procedure section and be able to duplicate your results without having the lab manual present.  Do not do any calculations in this section, just record how you performed the experiments and record the raw data.  If the data is taken by computer, you must specify the path and filename where the data is stored.   This information must be listed in this section right after the description of how the data was taken.  Do not simply list all of the files generated at the end of the section.

This section MUST be signed by the instructor before you leave the lab.  If you turn in a report without the signature, it will not be accepted!

*Analysis - a sample of the calculations made in the lab.  **This section should include a sample of the error calculations and propagation of errors used in your analysis.   The final data that you are analyzing to generate conclusions, the values with appropriate uncertainties, must be shown in this section.  The actual calculations for each one does not have to be included, as long as you show an example for one, but you may include them all if you wish.  The calculations may be done by the computer, but include printouts of the worksheet in your lab book.  Any graphs or printouts that are placed in your notebook must occupy one whole page and be trimmed to fit within the page and not hang outside of the notebook.

*Conclusion - this section must have a conclusion that is based on your experiments and analysis.  If your conclusions do not following logically from your analysis, your grade will be deducted significantly.  This section must also contain a brief description of significant factors that you think affected your data, in particular, the uncertainties in your data (factors that contributed to the error in your experiment).  A good thing to keep in mind is to think of this report as a report you are submitting as part of your job responsibilities.   If you do not think your boss would accept what you have to say, it is a safe bet that I will not like it either.

The asterisks indicate the sections that I will pay particular attention to when grading.

Modified April 17, 2015 by Galen C. Duree Jr.