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Introduction to Fundamental Physics Laboratory Lecture II

Learn to graph I-V curves for diodes and magnetic field distribution in solenoids. Understand figure drawing techniques for scientific data visualization.

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Introduction to Fundamental Physics Laboratory Lecture II

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  1. Introduction to Fundamental Physics LaboratoryLecture II Dr. Yongkang Le March 5th, 2013 http://phylab.fudan.edu.cn/doku.php?id=course:fund_phy_exp:start

  2. Example：Density of a metal cylinder Mass measured with an electronic balance: M=80.36g, d =0.01g, a =0.02g. Height measure with a ruler:H＝H2－H1, where H1＝4.00cm, H2＝19.32cm；d =0.1cm，uB1 =d /5；a =0.01cm. Diameter measure with a vernier callipers (D data are given in the table); d =0.002cm；a =0.002cm。 Please calculate the density and its uncertainty.

  3. For height： Average value of the diameter： Uncertainty estimation： For mass：

  4. Density ： Results：

  5. Draw a figure Why? 1、Show the qualitative relationship 2、Illustrate the different characteristics 3、Derive the useful information Get the slope through graphing I-V curves for two diodes Magnetic field distribution along the axis of solenoid

  6. How to draw a figure • Select a proper graph paper（usually standard graph paper 20×25cm2、scaling should match the significance digits、not smaller than half of a graph paper） • According to the value range of the physical quantities, decide the scaling(1:1,1:2 or 1:5; but not 1:3, 1:7) • According to the variable relationship (independent-dependent), select orientation of the graph paper (take the independent variable as abscissa) • Draw axis, scale division (homogenous, not too close), and mark the name of the physical quantity (italics) and its units (roman style) • Draw data points with symbols (do not mark the data values) • Draw a straight line or curve, mark the points for readout for evaluation, usually also their coordinates (for slope, peak, valley, etc.) • Write down the information of author, lab name, graph name, date

  7. Example:

  8. How to read out from a figure 1、 Mark the readout point, usually select the crosssection of the curve with X-grids(do not take the original data points), with a symbol different from that for data point. Mark its coordinates (X,Y). 2、To read out a single coordinate, X or Y value, mark the unit together with the coordinate. 3、To get the slope of a straight line, the two readout points should be far away from each other, but in the scope of experimental data. Don’t forget the unit of the slope.Calculation should be carried out in the report but not in the figure. 4、The read coordinates should always have the correct signifcance digits.

  9. Example: Experiment：Frank-Hertz experiment Figure：Ip-UG curve Author：Shiyan Hao Date：03/09/2010

  10. Data got from Voltage-Current experiment: What’s wrong? What fails? • Possible answers • The axis name and the unit of the quantity fails • Scale of the Y-axis is 1:120----wrong • Figure description • Different symbols for different series of data • Insert legend for different series of data • Not necessary to go through the origin • If necessary, read out

  11. The purpose of this course 1. Master the basic knowledge, the basic approach and basic skills of physics experiments. 。 2. Learn to investigate the physical laws by the experimental method, to deepen understanding and mastery of physical laws, and enhance the ability to raisequestions in the experiment, analyze and solve problems. 3. Cultivate the scientific attitude

  12. Important Notice! Evaluation of experimental data must be strict, careful, accurate and true.

  13. General Guide 1、Evaluation over the whole process: preparation, lab work and report 2、Don’t fail a lab or a report! Arrive in time! 3、Try to understand the lab and to enjoy the lab. Try your best to find something new in the labs. 4、Safety! ------ Highest priority!

  14. How to do experiment? 1、Pre-lab preparation（20%） 2、Operation and record（40%） 3、Data Processing and Analysis/Discussion （40%） On the cover of the notebook： name、student ID ..

  15. Pre-lab (20%） • It is not allowed to do experiment without pre-lab report! • Every 10 minutes late for -0.5 points; more than 30 minutes late, then not • allowed to do experiment and get 0 point for this experiment. • Asking for absence must be done in advance, no make-up otherwise. Pre-lab • How to prepare the pre-lab? • Read the lab manual carefully and try to figure out how to carry out the lab. Visit your lab in advance will always be helpful. (Lab-open on each Tuesday afternoon) • Write the pre-lab report. Experiment title Purpose： Principle： (Including backgroud, theory, important formula, circuit and ray diagram) Content and procedures： Briefly! Prepare the table for record! • Suggestions • Write report is something you should learn and practise. • Always try with your own words • A report consists all the important items, should be brief and easy to be understood ..

  16. Suggestions for drawing a data table 1、To find out how many physical quantities you are going to measure? Which is a directly measured quantity, which is derived by calculation? Which should be measured several times? Which should be measured once (Multiple measurements should normally be 10 times or more; but due to limited time, 5 times in our lab.) 2、The table should be reasonably arranged according to the carry out of the lab. List the directlymeasured quantiyies first, then the calculated ones. For multiply measured quantities, enough places should be left in the colum. List the independent-quantities before the dependent-quantities. 3、Mark the physical quantities(their symbols and units). The symbols should be written in italics style and the units in roman style, respectively. 4、Write down the related formula for calculation in the near of the table.

  17. Example：Measuring the density of a cylindrical sample The mass of the sample: M=g。 Room Temperature=℃；Humidity =%。

  18. Lab work （40%） • Following the guide and pay attention to the safety. • Carry out the lab with confidence, but cautiously and seriously • Wirte the lab record faithfully, clearly and in detail. Contents including operation, parameters, phenomena, measured data, findings, reasoning, new ideas, doubts etc. • Notice: Detailed and timely! • To ensure the originality of all the data: any change of the data should be accompanied with a notification. No scratch of your labbook. • Write down the specifications of your equipments. • You are encouraged to try the optional contents. • Arrange your lab equipment properly and let your supervisor have a check before you leave. In the lab Experiment record： （fill the table） （record the condition, phenomena, data, problems and ideas, etc. ) Equipment： （ specifications and models??）

  19. After the lab Report （40%） 1、Finish the data evaluation with uncertainty estimation. 2、Explain the phenomena you observed correctly, give your own reasoning. 3、Interpret the experiment results carefully(own understanding). 4、Draw a conclusion. 5、Further discussion, comments and suggestions. Evaluation： Discussion： Conclusion： Further discussion, comments and suggestions： ..

  20. Question? Thanks! Let's have fun together in labs!

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