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How to Report on an
Experiment
A laboratory report should communicate, as clearly and concisely as possible, the rationale for the experiment, what was done, what the results were and what the results mean. On the basis of a report on an experiment a reader should, basically, be able to repeat it and get similar results. The report should be as short and simple as possible to accomplish these ends; it takes practice to learn how to write a technical report which does this well.
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Any report must have certain content to accomplish the above purpose and to facilitate the administration of the course. While the specific format outlined below is not essential for this, it is one way to accomplish it and students should find following it to be useful and instructive. However, as long as the objectives above are accomplished, this scheme may be reasonably modified for certain labs if desired. For instance, if an experiment has several parts which use different apparatus or if the same apparatus is used to do several different experiments, the material in some sections may need to be repeated for the various different situations and this should be organized in the most suitable way.
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Heading:
Identify the experiment by name and give the date performed, your name (first and underlined) and that of your lab partner(s), and lastly the name of your TA. |
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Abstract:
Give an extremely short (only a few sentences) description of the object of the experiment and a statement of your principal results.
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Theory:
Start with the motivation (or reason) for the experiment. Follow this with the theory behind the experiment. Give a brief presentation, in your own words, of the essential ideas behind the experiment. Include only the most important formulas (explaining the meaning of any symbols used). Do not give any derivations unless they are original. The purpose is just to establish the context of the experiment and state, for reference, the relations you will be using in analyzing your data. (The proverbial interested reader should be able to look up details elsewhere on the basis of your outline.) One paragraph, in good English, should suffice.
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Experiment:
Succinctly describe, in your own words, the apparatus used and the procedures followed to get your results. It is best to do this without reference to the lab manual. Relying on your own memory is more authentic and provides practice for your powers of observation. Tell what you did so that someone else could duplicate it from your description. Obviously, neither your teacher nor the other students need this exposition (anymore than they need your solutions to the homework problems for the lecture part of the course); they all know about the experiment. This is an instructive exercise, for your benefit, in attending to and understanding facts in a scientific manner and to give you practice in describing them intelligibly. Think of your reader as an intelligent physics student who has not done the experiment. You should demonstrate clearly to your teacher that you know and understand what you did and can articulate it simply. Often the simplest and clearest way to explain something is to give a schematic drawing. This means a drawing without the details that are not essential to the point you are trying to communicate. It is important to gain the skill of realizing and illustrating the essence of a situation. This will also make it easier for the teacher to read and understand what you write. So you are encouraged to use such drawings and you should include one of the apparatus used. However, do not copy the detailed diagrams in the lab manuals directly, a rough sketch of the apparatus showing the relevant physical variables (e.i. x, y, [[theta]], etc.) is appropriate. Emphasize sketches of the equipment but three dimensional artist's sketches are inappropriate. Such a drawing should illustrate what you have to say.
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Data Analysis:
Give one example of each calculation made; it should be clear that you understand what you are doing. You may do the other calculations separately and include only the final results. For your own benefit (and for the instructors sanity): BE NEAT! Calculate errors and show any error formulas used; again, include one sample calculation.
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Clearly state the results you obtain. Data should be presented in an organized form, such as in tables, charts and graphs, and stated in correct SI units. Do not use the tables from your original data sheets for this purpose. All data is to be recopied and reformatted in the Data Analysis section of the write-up. Experimental data should be compared to theoretical predictions and calculations. Include the error analysis (such as standard deviations and uncertainties) in your tables and with your final results. For help on error analysis, see the Error Analysis section in the lab manual. See the section on Graphs and Curve Fitting in the lab manual for an explanation on obtaining results from your graphs and data. If a book value for the measurement is available, state the number of standard deviations that your result differs from the accepted value.
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Conclusion:
Summarize, in a paragraph or two, what you conclude from the results of your experiment and whether they are what you expected them to be. Compare the results with theoretical expectations and include percent error when appropriate. Don't use terms such as "fairly close" and "pretty good;" give explicit quantitative deviations from the expected result. Evaluate whether these deviations fall within your expected errors and state possible explanations for unusual deviations. Discuss and comment on the results and conclusions drawn, including the sources of the errors and the methods used for estimating them. Include brief answers to the specific questions asked in the lab instructions.
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Remarks:
Please critique the experiment as presented in the lab manual. Could the lab be done in a better way? Do you have some other or original method for obtaining the same results? Your suggestions are encouraged and are used to improve the lab manual.
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Data: Attach a copy of the initialed data which you took in the lab to the back of your lab write-up. |
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