Source: Physics 212 Lab 4 Activity v1.2, Appendix 1 | Course: University Physics: Electricity & Magnetism
Tags: testing experiment, claim testing, scientific report, lab report, prediction, uncertainty, IOLab, schematic diagram, data annotation
Difficulty: Introductory | Prerequisites: None beyond basic familiarity with lab equipment and the scientific method. Useful for any PHYS 212 lab from Lab 4 onward.
Lab 4 is the first time PHYS 212 asks you to write a full scientific report and to follow a structured process for testing a claim with quantitative data. These skills recur in every subsequent lab. The testing-experiment framework gives you a repeatable method: assume the claim, predict what data should look like, collect data, compare, and decide. The report structure (introduction, methods, results, discussion, conclusions) mirrors the format used in professional scientific papers, so learning it now pays off well beyond this course.
A testing experiment has five steps: accept the claim temporarily, design an experiment, predict the outcome, run it, and decide whether the data supports or rejects the claim. Your lab report documents each of those steps in five sections (introduction, methods, results, discussion, conclusions), with annotated figures and numerical data including uncertainty.
Claim
A testable statement about how something in the physical world works. In Lab 4, the claim is: "Charge can move between capacitors, but as long as the DAC is disconnected the total charge is conserved." In simple terms, it is the specific thing you are trying to prove or disprove.
Testing experiment
An experiment designed so that its outcome can be predicted from the claim. If the prediction matches the data, the claim is supported. If not, the claim is rejected (or the experiment needs refinement).
Prediction
What you expect the data to show if you assume the claim is true, stated before collecting data. For Lab 4: Q_before should equal Q_after within experimental uncertainty.
Uncertainty
A quantitative estimate of how much your measured value might differ from the true value. Expressed as ± some amount (e.g., 0.95 V ± 0.02 V). Comparing two quantities "within uncertainty" means checking whether their uncertainty ranges overlap.
Schematic diagram
A simplified drawing of a circuit using standard symbols for components (capacitors, voltage sources, ground, measurement points). Required in the Methods section of your report.
Annotation
Labels, arrows, or markers added to a graph or screenshot to highlight important events (e.g., "DAC turns on," "capacitor disconnected"). Required when presenting IOLab data in your Results section.
Quantitative result
A numerical measurement or calculation with units and uncertainty, as opposed to a qualitative observation like "the voltage went down." Lab 4 requires quantitative results to test the claim.
Temporarily accept the claim as true. You are not assuming it is correct forever. You are assuming it long enough to figure out what the data should look like.
Design an experiment whose outcome the claim predicts. For Lab 4: charge one capacitor, disconnect the source, add uncharged capacitors in parallel, measure voltages, calculate charges.
Make a prediction. State, in numbers, what you expect. Example: "If charge is conserved, Q_before = C_1 × V_initial should equal Q_after = (C_1 + C_2) × V_final."
Conduct the experiment and compare. Collect data, do the calculations, and see whether the prediction and the result agree within uncertainty.
Decide: accept or reject the claim. If prediction and result agree (uncertainty ranges overlap), the claim is supported. If they do not agree, the claim is rejected, or there may be a systematic error worth investigating.
Introduction (one paragraph)
Tell the reader what the report is about.
Name the claim being tested.
Briefly summarise your method and main finding.
Methods
Describe the circuit setup with a schematic diagram.
State the DAC voltage setting and what was connected to the IOLab.
Explain what you changed in the circuit and when (e.g., disconnecting the DAC, adding capacitors).
List the equations you will use (Q = CV, C_total for parallel capacitors).
State your prediction: what the data should show if the claim holds.
Results
Present IOLab data with annotated screenshots or graphs.
Mark key events on the graphs (DAC on, DAC disconnected, capacitors added).
Report numerical voltages with uncertainty.
Show charge calculations (Q_before and Q_after) with uncertainty.
Note any difficulties or unexpected observations.
Discussion
Describe what you observed in plain language.
Compare the results to your prediction. Do Q_before and Q_after agree within uncertainty?
Explain the physics behind what you see. Why does the voltage drop? Why is charge conserved?
Conclusions
Summarise the experiment and findings in a few sentences.
Explicitly state whether you accept or reject the claim, and why.
Mention any further experiments that could strengthen the result.
Take screenshots of the IOLab software showing voltage vs. time for the DAC output, the capacitor voltage, and GND.
Add annotations (text labels and vertical lines) to mark when you turned the DAC on, disconnected the DAC wire, added capacitors, etc.
Use the IOLab's highlighting function to select a region and display statistics (mean voltage, standard deviation).
Every figure needs a caption explaining what it shows. Refer to figures by number in your text.
"If my data doesn't perfectly match the prediction, the claim is wrong." Measurements always have uncertainty. The question is whether the prediction and result agree within those error bars. Perfect agreement is not expected.
"The prediction is just a guess." The prediction is derived from physics and the assumption that the claim is true. It is a calculated expectation, not a shot in the dark.
"I only need to show my final answer, not the raw data." The report requires both: raw IOLab voltage data (with annotated figures) and calculated quantities (charge values with uncertainty).
"A schematic diagram is optional." It is required. The Methods section must include a circuit diagram showing how the components were connected.
⚠️ The five-step testing-experiment framework is reused in every remaining PHYS 212 lab. Learn it once, apply it repeatedly.
⚠️ Reports are graded on whether you state the claim clearly, make a quantitative prediction, present data with uncertainty, and explicitly accept or reject the claim. Missing any one of these costs marks.
⚠️ Annotated figures are not optional. Unmarked screenshots without labels or captions will lose points.
⚠️ The Discussion section is where most students lose marks. You need to compare results to prediction with numbers, not just say "they were close." Spell out whether the uncertainty ranges overlap.
True or False: The prediction in a testing experiment is made after collecting data. (False, it must be made before.)
Fill in the blank: If the prediction and result agree within ________, the claim is supported. (experimental uncertainty)
True or False: A lab report's Methods section should include a schematic diagram. (True)
True or False: In the Conclusions, you should state whether you accept or reject the claim. (True)
Fill in the blank: To annotate IOLab data, you add ________ to screenshots indicating important events. (labels, arrows, or vertical markers)
Q: What are the five steps of a testing experiment, in order?
A: (1) Temporarily accept the claim. (2) Design an experiment whose outcome the claim predicts. (3) Make a prediction. (4) Conduct the experiment and compare the outcome to the prediction. (5) Decide to accept or reject the claim.
Q: Your prediction says Q_before = 95 ± 3 µC and your measured Q_after = 89 ± 4 µC. Do you accept or reject the claim of charge conservation?
A: Q_before ranges from 92 to 98 µC. Q_after ranges from 85 to 93 µC. The ranges overlap (92 to 93 µC), so the claim is supported, though the overlap is narrow and you might note that improved measurements would strengthen the conclusion.
Q: A classmate's report states "the charge was about the same before and after" without giving numbers. What is missing?
A: Quantitative results. The report needs the actual calculated values of Q_before and Q_after, their uncertainties, and an explicit comparison showing whether the ranges overlap.
Q: Why must you state your prediction before collecting data?
A: To prevent bias. If you see the data first, you might unconsciously adjust your "prediction" to match it, which defeats the purpose of testing the claim.
Q: What belongs in the Discussion section that does not belong in the Results section?
A: Interpretation and explanation. Results presents the data and calculations. Discussion compares those results to the prediction, explains the physics, and considers whether anything was surprising or problematic.
The testing-experiment framework applies to every lab in PHYS 212 (and most experimental science courses). The report structure (introduction through conclusions) mirrors the format of published research papers, so practising it here builds a transferable skill. Uncertainty analysis connects to statistics and error propagation, which you will use more rigorously in later labs. The idea of comparing a prediction to data within error bars is the same logic behind hypothesis testing in statistics courses.
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