PH 202 Laboratory – Summer 2015
Instructor:
Mr. Michael Boleman, M.S.
Office: ILB 108
Office Hours: Mon. & Wed. 11:00 – 11:30 and Mon. – Thurs. 12:30 – 1:00
Phone: Off campus: 460-6224 Ext. 1544; On Campus: 6-1544
E-mail: mboleman@southalabama.edu (Preferred Method)
Web page: physics.southalabama.edu → Classes → Lecture Notes → Mr. Boleman
Lab Manual: Physics Experiments for PH 201 & PH 202, 5th Edition (May, 2014)
Week of:
May 27 – 28
June 1 – 2
June 3 – 4
June 8 – 9
June 10 – 11
June 15 – 16
June 17 – 18
June 22 – 23
June 24 – 25
June 29 – 30
July 1 – 2
July 6 – 7
July 8 – 9
July 13 – 14
July 15 – 16
Experiment Number
---1
2
3
4
No Labs
5
6
7
8
July 4 Holiday – No Labs
9
10
11
12
Topic
Course Introduction
The Electric Field
Capacitors
Ohm’s Law & DC Circuits
Kirchhoff’s Rules
e/m of the Electron
Faraday’s Law
RL Circuits
AC Circuits
Geometric Optics
Lenses & Spherical Mirrors
Diffraction
Interference
Course Objectives:
As with any laboratory course, the hope is that conducting hands-on experiments in the lab will help deepen your
understanding of the material you are learning in lecture. In addition, the lab reports you write should help improve your
scientific and technical writing skills.
Attendance Policy:
You may make up a missed lab if:
1. You have a valid reason for missing class (as determined by me).
2. You are able to attend another lab section during the week of the missed lab.
3. You obtain permission from the instructor of the class you will attend to make up the lab.
Lab Reports:
There are 12 lab experiments for you to perform this semester. Your grade for each experiment is determined
from a preliminary assignment, which you must complete prior to coming to class, and a six-section formal lab report,
which you write in class.
The preliminary assignment is located at the end of each lab in the lab manual. The preliminary assignment
questions are experimental in nature. For each assignment, you are given a sample set of data to analyze. This means that
you will need to read the lab carefully in order to answer the questions. Preliminary assignments must be turned in at
the beginning of class, before the lab introduction.
Your lab report will be hand written in class and must be turned in by the end of class. Each lab report must
include the Title, Introduction, Equipment, Theory, Data, Calculations, & Conclusions sections. These sections are
explained on pages 14-15 in the lab manual. See pages 15-18 for a sample lab report.
When writing your reports please note:
1. Write on the front of your paper only.
2. The data in your Data section is shared with your lab partner.
3. All sections of the lab report MUST BE YOUR OWN WORK. Discussions with your lab partner are
encouraged, but do your own work.
4. The points awarded in each section are based on the inclusion or omission of the required elements as well as
grammar, spelling, neatness, and overall presentation.
Grades:
Each lab report is graded out of a maximum of 20 points according to the following scale:
Preliminary Assignment (10%)
Title
Introduction (5%)
Equipment (5%)
Theory (10%)
Data (25%)
Calculations (25%)
Conclusions (20%)
Lab grades will be posted on USA Online (a.k.a. Sakai).
Your final lab grade is the average of all 12 lab reports (There is no ‘drop grade’). Your final lab average is converted to
a 100-point scale and is counted as 15% of your overall course grade.
At the beginning of each class, I will return your graded lab report from the previous week. At the end of class, you must
turn in both your current lab report as well as the graded report from the previous week. I will keep you graded reports on
file, and they will not be returned.
Students with Disabilities:
“In accordance with the Americans with Disabilities Act, students with disabilities who are registered with the
Office of Special Student Services will be afforded reasonable accommodations in completing lab assignments.”
Important Note:
It is the policy of the Physics Department that you must have a passing laboratory average (≥ 60%) in order to
pass the course.
The Lab Report
•
Title
•
Introduction: Clearly explain the purpose of the experiment. What physics are we studying? Do not get into the
specifics of how to do the experiment at this point. Just briefly describe the purpose of the experiment.
•
Equipment: List the equipment used in experiment.
•
Theory: Describe the physics theory. Note that you do not need to use any resources other than your lab manual.
•
•
•
•
•
Discuss the main physics concepts.
Include all equations used and define the variables. How are these equations obtained?
Write in your own words. (I.e. do not copy the lab manual).
Try to explain the theory without discussing the particulars of the experiment itself. That is, do not
explain how to prove the theory experimentally, but rather, explain the theory itself.
Data: In this section, you want to explain the actual experiment and record your measurements.
•
•
•
Draw a sketch of the experimental setup.
Briefly describe the experiment, and explain how you obtained your data.
Include neatly organized data tables and any printouts from the computer.
•
_
If the statistical uncertainty is calculated for a set of data, then record the average x , the standard
deviation σ and the statistical uncertainty δ x =
•
N
next to the data table.
Calculations:
•
•
•
•
σ
Work one example of each type of calculation, including error analysis calculations. The one exception
to this is statistical uncertainty. You do not need to show the calculation of an average, standard
deviation, or statistical uncertainty.
Use transitional text between equations.
Work in SI units. (Meters, Kilograms, Seconds)
Conclusions:
•
•
Report your results and draw conclusions based on those results. Do your results provide evidence to
support the physics theory you are investigating?
Discuss “sources of error”. Note that “source of error” does NOT mean mistake. Think about
‘experimental limitations’. Do not give a list of mistakes that you may have made along the way, but
rather think about the nature of the measurements. What is the largest contributing factor to the total
error? If you had to do the experiment again, what could be done to improve the precision of
measurements? Are there assumptions made in the theory that are not strictly true in the real world?
Finally, never, ever, never, ever say “human error”! It’s a meaningless phrase.
Measurement Uncertainty & Error Propagation
All measurements have an uncertainty. For example, suppose you measure the width of a table to be 10.2cm. Suppose
too that the instrument you used to measure the width has an uncertainty of 0.05 cm. In your data section, you should
record that measurement as W = (10.2 ± 0.05) cm. This means that given the instrument you used you measure W, you
can at best say that W is between 10.15cm and 10.25cm, or to be more concise, (10.15 ≤ W ≤ 10.25) cm.
Measurement Uncertainty: Assign an uncertainty to every measurement you make.
Suppose that you measure a value A. It has an uncertainty δA (delta-A). The uncertainty you assign to the measurement
depends on how you make the measurement. For each measurement, the uncertainty in that measurement will be either:
1. Instrumental uncertainty: (Use instrumental uncertainty if you make a single measurement of A.)
i. If A is measured with an analog instrument, then δA = ½ least count.
ii. If A is measured with a digital instrument, then δA = last decimal place of the instrument’s display.
2. Statistical uncertainty: (Use statistical uncertainty if you make many measurements of A and calculate an
average value of A.)
The uncertainty of the average value of A is given by δA =
σ
, where N = number of measurements in the
N
average and σ = Standard Deviation.
3. Estimated uncertainty: Use estimated uncertainty when neither 1 nor 2 make sense. I will explain this as it
occurs.
Error Propagation: Use error propagation to determine an uncertainty for every calculated value.
Since all measurements have an uncertainty, then certainly the results of calculations made using these measurements
must also have an uncertainty. Error propagation is the means by which you determine the uncertainty in a calculated
result.
1. Addition / Subtraction: Add absolute uncertainties.
•
For example, if D = A − B + C then δ D = δ A + δ B + δ C .
2. Multiplication / Division: Add relative uncertainties.
•
For example, if D =
A⋅ B
δ D δ A δ B δC
 δ A δ B δC 
then
. Therefore, δ D = 
=
+
+
+
+
⋅ D
C
D
A
B
C
B
C 
 A
3. Functions
•
i.e. C = tan(A), C =
A
, etc. Refer to the introduction section of the lab manual for these special cases.
B
Comparison of results with theory
In order to conclude that you have successfully proven a theory, the data must agree with the theoretical expectation
within uncertainty. Just having a result that is “close” is not enough. For two values X and Y to agree within uncertainty,
they must agree within three standard deviations. That is, to conclude that X ± δ X agrees with Y ± δ Y , we require that
X−Y
≤ 3.
δ X +δ Y