Physics 271L
Electricity and Magnetism Laboratory

Physics 271L Coordinator: Physics 271L Lab Instructors:
Prof. T.E. Clark A.M.: Shu-Ju Tu     P.M.: Matt Long
Office: Room 254, Physics Bldg. Office:TBA
Office Telephone: 49-43038 Office Hours:TBA
e-mail: sjtu@physics.purdue.edu     
             mlong@physics.purdue.edu

GENERAL INSTRUCTIONS

[Requirements | Grading | Lab Reports | Significant Figures ]

The laboratory is designed to give you experience with the physical applications of the theory you will receive in lecture and recitation, and to introduce you to some techniques of data analysis.


I. The requirements of the laboratory are as follows:

A. Attendance is required for each lab period. Attendance will be taken for each lab period.   If you miss a lab due to illness, etc., you must make up the lab.  You are responsible for arranging a lab make-up session with the lab instructor. If you fail to make up a missed experiment, you will receive an Incomplete.  It is the responsibility of the student to be aware of the University regulations regarding an Incomplete.

B. You will be required to make a brief report for each experiment. This report must be made individually by each student and will include the data taken during the experiments, calculated results, graphs, tables and any conclusion you arrive at as a result of performing the experiment.  The lab reports are to be turned in on time as indicated in the Schedule and below in section III.  A late report or no report will result in a lowered grade.  A grade reduction of 5% per day for late reports will be made down to a score of  0% for that lab report.

C. You must prepare for the experiments before lab time since you will be expected to know the main ideas of the theory and procedure. Each instruction sheet will contain a complete description of the experiment (usually with schematic diagrams and/or pictures) and the procedure. You should make a special effort to be able to recognize the equipment from the drawings and pictures in the write-up. A SHORT QUIZ OVER THE EXPERIMENT'S IDEAS AND/OR PROCEDURES MAY BE GIVEN AT THE BEGINNING OF EACH CLASS.
You are also expected to bring your own calculators, graph paper, straight edges, etc. These will be listed as needed at the beginning of each write-up.


II. The grading for the lab is as follows:

10% - Based on the short lab quizzes at the beginning of classes.



90% - Based on the lab reports, the instructors evaluation of 
	the preparation for the laboratory, and the general understanding 
	shown by the student for laboratory work.


III. Lab Reports:
Lab reports are due as stated on the Schedule. An experiment is not complete until a report is turned in.  Reports must be turned in on time. A grade reduction of 5% per day for late reports will be made down to a score of  0%(zero percent). Turn reports in directly to your instructor at the beginning of the class on which they are due. Write your reports on one side only of a 8 1/2 x 11 paper. Clearly state on the front of the report the experiment for which it pertains, along with your name, Physics 271L and the date. Failure to precisely follow these instructions will result in lost reports and the necessity of repeating the experiment.

The In Class Reports (see Schedule) should be abbreviated versions of the full lab reports which follow the laboratory report outline given below.  Prudent time management is essential in order to complete the in class reports.  Although abbreviated, in class reports should include a sentence of purpose and procedure (a diagram is often sufficient), and a concise analysis of the data, which should include a discussion of error, sufficient to compare and contrast with the expected results. 

In your work you will often be using fairly expensive equipment, $150 meters for example. Be aware of this and have your lab instructor check your set-up before you start to work. Do not plug in circuits to the power supply until the circuits have been checked.

Physics 271L Laboratory Report Outline

  1. Title Page: This includes Physics 271L, the experiment number and title, your name, your lab partner's name,  the date the experiment was performed and the date the report is being turned in.
  2. Purpose/Objective: In your own words describe what it is that you are investigating in the experiment.
  3. Procedure/Data: Before each set of measurements, briefly describe how the measurements were made. If you have to construct a circuit, include the diagram of the circuit. ORGANIZE your DATA neatly into tables with columns. USE A RULER!
  4. Graphs/Calculations: For some data you may be asked to graph the data to obtain a straight line indicative of a particular theoretical relationship. On the graph include: 


    	*When calculating slope and intercept, it is acceptable 
	to use the least squares fitting provided on many 
	calculators. If you choose L.S. Fit,  then please 
	indicate as such. Otherwise, calculate slope & 
	intercept from your best line through your data points. 
	DO NOT use a data point in your slope calculation, 
	take points from your line.
  5. Graphs/Calculations cont'd.: Any manipulation of data involving anything more complex than a single multiplication, show first the symbolic manipulation and then substitute one pair of data points.
    example:

                                                        symmbolic manipulation          data points

  6. Conclusion/discussion: When you have finished all of the above, then conclude the report.  What did you learn?  Does this confirm the theory?  What can be done to improve the experiment?  What is the error involved with these measurements?   What are the sources of error?

Significant Figures

When taking data, the numbers recorded and the calculations made with them are not known with unlimited precision. The term "significant figures" is used to indicate the precision to which a given number is known and includes all digits in that number which are known with certainty plus the first uncertain digit.

Rules for Determining Significant Figures

  1. All non zero digits are significant.
  2. All zeros between non zero digits are significant.
  3. Zeros to the right of a non zero digit are significant ONLY if specifically indicated to be so or if they precede a decimal point.
            ex. 500 generally would be considered to have 1 significant figure.
  4. All zeros to the right of a decimal point and which are not preceded by a non zero digit are not significant.

            ex. 0.03 has 1 significant figure.

                 1.005 has 4 significant figures.
  5. All zeros to the right of a decimal point and to the right of a non zero digit are significant.

            ex. 1.00 has 3 significant figures.

                  .050 has 2 significant figures.
  6. Notation using powers of 10 may aid in noting the numbers of significant figures. This allows the placing of the decimal point according to the preceding rules. Combining rules 5 and 3, if 500 were given to 3 significant figures, one would write 5.00 x 102.   If it were known to 1 significant figure, it would be given as 5 x 102.

Operations Using Significant Figures and Propagation of Error

  1. Addition and Subtraction
    The right most significant figure in a sum or difference occurs in the left most place at which a doubtful figure occurs for the measurements involved. The uncertainty in the sum or difference is the sum of the absolute values of the individual uncertainties.
    In this example, the result would be recorded as 119.4 ± .1, since the left most place in which a doubtful figure occurs in the first decimal place. The number must be rounded off to that digit. Usually rounding off consists in raising the last significant digit by 1 if the digit to its right is between 5 and 9, otherwise leaving it as it stands. Had the first number in the example been 3.90, the result of the example would have been 119.5 ± .1.
  2. Multiplication and Division
    The product or quotient is known to the precision of the number of significant figures in the least precise factor. The uncertainty is the percentage equal to the sum of the individual percentage uncertainties.

  3. Calculations involving polynomials and transcendental functions.
    If a quantity y has an uncertainty Dy, then the uncertainty in yn is given by

    or

    .

    The uncertainty in lny is

    .

    The uncertainty in sin(y) is

    .

    These are approximations with y small compared to y.